Exploring the Appeal of Electric Vehicle Interior Design from the Perspective of Innovation

Abstract

Electric vehicles now play a critical and promising role in the automotive industry. This study presents how electric car interiors innovatively appeal to consumers’ needs, influencing their preference for interior design based on essential features. It investigates why consumers prefer the interior design of electric vehicles and what specific characteristics influence these preferences from the perspective of innovation. This study applies a preference-based research method to determine the significance of the innovative appeal of electric cars. The evaluation grid method is applied to interpret experts’ professional insights, which are outlined using a semantic hierarchical diagram of electric vehicle interiors. This study also conducts a questionnaire survey based on consumers’ reactions and analyzes their answers using Quantification Theory Type I. The four key original evaluation items for electric car interiors are determined as “tasteful,” “avant-garde,” “technical innovation,” and “sustainable innovation.” These four factors can be applied using their corresponding reasons and characteristics. This study contributes critical suggestions for interior designers and researchers of electric vehicles. The study also provides useful information on user-centered interaction design, sustainability, and consumer psychology.

1. Introduction

EVs are at the forefront of the automotive sector’s transformation, reshaping technology, market dynamics, and sustainability trajectories and underscoring their central, forward-looking role in the car market. A 2024 systematic review synthesizing 88 studies concluded that EV uptake is materially advancing environmental and policy goals while reconfiguring industry practices [1]. Global EV sales reached more than 10 million vehicles in 2022 and were expected to grow to 14 million vehicles in 2023 [2]. Today, humans are facing various environmental challenges, with attempts being made to solve them through environmental protection and energy-saving solutions. The development of electric vehicles (EVs) could be viewed as a practical and effective solution and is becoming a dominant trend.

However, developing EVs for environmental reasons is not closely connected to humans’ daily lives and is insufficient to influence consumer preferences, since they have to consider various practical needs, such as functions and usability. Therefore, providing EV consumers with choices that align with their desires is a key challenge for EV manufacturers. This study endeavors to prove that the progressive appeal of EVs can motivate consumer preferences. For example, the Ford Mustang Mach-E features advanced and tech-laden interior design to create a futuristic impression for EV consumers [3]. In addition, the BMW i7 applies some special materials to create a modern and novel EV atmosphere, according to the IEA’s annual Global Electric Vehicle Outlook [2]. This evidence indicates that EV manufacturers are attempting to attract consumers by applying fashion design characteristics to car interiors. Furthermore, there is a clear trend toward creating smoother and more elegant surfaces in car interiors to provide consumers with the impression of a futuristic appearance [4]. This point of view reveals a possible development direction for electric car interior design.

Consumer preferences and considerations regarding car interiors are always changing; therefore, motivating their needs and evoking their concepts of sustainable design, based on the advantages of EVs, could be a key focus for manufacturers. However, transferring customer expectations of internal combustion engine vehicle (ICEV) interiors to EV interiors could be a significant engineering challenge because drivers’ long-held concepts and preferences are not easy to change. Hence, making a prospective impression on consumers using EV interiors and increasing their purchase motivation based on their emotions inspired me to study this research topic. This study focuses on consumer preferences related to innovation and excludes other factors, such as their ergonomic preferences. Hence, related fields, such as aesthetics, fashion, sustainability and innovation, are also studied in this article. Furthermore, this study uses the concept of “innovation” to inspire consumer interest in EV interiors, reflecting the point of view of Jochen Paesen, Kia’s vice president of interior design, who argues that designing an “inspiring space” is critical for EVs [5]. However, designing an inspiring space is more difficult then describing it, as this involves motivating consumers’ feelings based on the advantages of EV interiors. In addition, incorporating innovative features in EV interior design to attract consumers is necessary for car manufacturers.

Customer-based design of EV interiors is becoming increasingly valuable as EVs grow in popularity. Hence, more researchers have started to study EV interior design in recent years. A recent study emphasized that electric vehicle interior design is evolving with innovative information visualization strategies, such as displaying state-of-charge (SoC) within cabin spaces, to enrich user interactions and enhance the driving experience in EVs [6]. However, the study did not investigate the interaction between users and car interiors based on human emotions. In addition, Shen et al. studied the functional and usable appeal of interior design in relation to the crossover B-Car [7]. However, the factors that attract customers to crossover B-Car interiors are different from those for EVs. Crossover B-Car interiors attract consumers who prefer cost-effective designs to not only save money, but also to meet their practical needs. In contrast, EV interiors target consumers who prioritize pursuing a prospective experience. Unlike previous studies, this study aims to explore the appeal of EV interior design based on consumer feelings and preferences for innovation. Hence, this study focuses on the design characteristics inside EVs, including textures, technologies, decorations, innovations, and sustainability.

In addition to the consideration of saving energy, EVs are transforming the traditional interior design of ICEVs and appealing to consumers’ prospective emotions. This inspired me to study the appeal of EVs, including their unique styles and characteristics. Furthermore, strategies that inspire consumers’ sustainable, modern, and innovative feelings can be developed by gauging their psychological reactions to EV interiors. Hence, this study assumes that consumers prefer EV interiors because they are inspired by innovative design.

Furthermore, this study explores how EV interior design can motivate consumers’ emotions based on innovative characteristics. Therefore, it addresses the following three research questions related to consumer reactions:

• Why do consumers prefer EV interior design over that of ICEVs in innovative aspects?
• What innovative characteristics do EV interiors have that fascinate consumers?
• What are the implications of EV interiors that can guide the innovative design of automotive manufacturers?

I hypothesize that the innovative attractiveness of EV interiors has a significant connection with consumers’ emotions, cognition, and perceptions, further elevating consumer preferences. Compared to ICEVs, EV interiors attract consumers through the innovative concepts that provide a completely new experience. In addition, I found that various characteristics of EV interiors effect consumers’ psychological considerations. Hence, this study applied Miryoku Engineering as a technical method to depict the relationship network between consumers’ psychological needs and design characteristics. Furthermore, this study applied the evaluation grid method (EGM) to explore consumer preferences for EV interiors by determining the critical appealing factors and design characteristics from an innovative perspective. EGM, as a qualitative assessment tool, was conducted through expert interviews and semantic analysis in this study. Then, a questionnaire survey was conducted and analyzed through Quantification Theory Type I, a quantitative assessment tool, which was used to evaluate the importance each evaluation item.

• Research Gaps and Contributions

Although previous studies have examined aspects of car interior design, most of them have focused on ergonomics, usability, or comfort factors in internal combustion engine vehicles (ICEVs). Meanwhile, the emotional and psychological appeal of electric vehicle (EV) interiors, particularly from the perspective of innovation, has received limited attention. In addition, while some studies has explored functional design features, few have systematically linked design characteristics with consumer perceptions of innovation using a mixed-methods approach. This leaves a clear gap in our understanding of how innovative interior elements, such as flat and smooth surfaces, multi-screen displays, eco-friendly materials, and push-type electronic doors, shape consumer impressions and purchase motivation.

This study addresses these gaps and makes the following contributions. First, it applies a combined methodological framework of Miryoku Engineering, the evaluation grid method (EGM), and Quantification Theory Type I to integrate expert insights and consumer responses, providing a novel approach to analyzing the emotional appeal of EV interiors. Second, it identifies four key appeal factors—tasteful, avant-garde, technical innovation, and sustainable innovation—and clarifies how these are linked to specific design characteristics. Third, it provides practical guidance for designers and manufacturers by showing how innovative design can enhance consumer perceptions and differentiate EVs from ICEVs. Together, these contributions advance theoretical understanding in design psychology and offer actionable insights for the EV industry.

This article is composed of seven sections. First, the Introduction Section provides critical market information, motivations, issues, and definitions in this study for readers. Second, the Related Works section reviews critical studies in the fields of ergonomics, design, and Miryoku Engineering. Third, the Research Objectives Section expounds the purpose, critical issues, and methods used to attain the study’s goals. Fourth, the Research Method Section outlines how the EGM and Quantification Theory Type I are used to collect and analyze data based on Miryoku Engineering. Fifth, the Discussion Section provides an analysis of the results obtained from the research instruments used in this study. Sixth, the research findings, implications, and contributions are presented in the Conclusions Section.

2. Related Works

This section reviews the key literature related to car interior design, covering topics such as consumers’ emotions, fashion, sustainability, human–car interaction, innovation, and the theoretical basis of this study. Consequently, Section 2.1 explores the critical interaction issues to understand how consumers communicate with EV interiors. Furthermore, in Section 2.2, I review key articles related to innovative design, with a focus on sustainability and technology. In Section 2.3, this study explores design issues related to the evaluation of consumer experience. In Section 2.4, I introduce the application and achievements of Miryoku Engineering and explain how this theory is applied in the context of this study.

2.1. Human–Vehicle Interaction

Consumers’ emotional responses to vehicles often result from the interaction between the user and the car. In this context, the car interior serves as a bridge that facilitates this communication. Therefore, interior design plays a crucial role in shaping consumers’ emotions and perceptions. The effectiveness of this communication largely depends on the quality of the interior design. More specifically, the designer’s attention to interior elements significantly influences how consumers feel while inside a vehicle. Dembirbilek, for instance, investigated users’ emotional responses by examining how the “meaning” embedded in a product can be designed to “communicate” with them [8]. Moreover, the challenge of creating an attractive and livable car interior that emphasizes human sensibilities is a critical issue in automotive development [9]. The interaction between external stimuli and perceived characteristics within a car can be better understood through empirical investigation [10]. Additionally, the relationship between complexity (or the arousal potential of a stimulus) and consumer preference has been examined using the inverted U-shaped curve model [11]. Furthermore, a study examining electric concept car interiors investigated how user impressions emerge in relation to specific design elements. By employing a repertory grid technique, the research systematically analyzed the relationships between anticipated user experience and the visual components of EV interiors, reflecting a clear connection between design features and user perceptions [12]. These studies collectively demonstrate how product design elements interact with consumers and influence their emotional and perceptual experiences.

In addition to understanding the communicative relationship between consumers and car interiors, creating a positive emotional impression is another critical issue. Zeynali and Alppay, for example, aimed to improve user experiences of EVs by examining both user perceptions and the visual components of EV interiors [12]. Their work also highlighted the importance of consumer motivation in the decision to adopt EVs. While the aforementioned studies have explored how consumers interact with car interiors and what motivates their preferences, few have examined the specific role that emotions play in the process of human–vehicle interaction. This emotional dimension is the central focus of the present study.

2.2. Sustainable and Technological Innovation

In addition to understanding human–vehicle interactions, how electric vehicles can leave a favorable and innovative impression on consumers is a critical issue in EV design. Both sustainable and technological innovations have been shown to influence consumer attitudes toward EVs. With regard to sustainability, the idealistic appeal of environmental protection alone is often insufficient to motivate consumer behavior, even if such concepts receive public approval. Therefore, translating sustainable concepts into practical, design-driven solutions is essential for EV manufacturers. In response, researchers have begun developing sustainable strategies that align with brand positioning, mission, and goals in the electric vehicle sector [13]. However, transforming these strategies into actionable plans and tactics requires more than vague intentions; it demands practical, design-based execution. EV manufacturers must consider how to integrate efficient spatial planning, visual aesthetics, material textures, and technological applications into interior design in order to realize sustainability. Therefore, innovation plays a vital role in bridging the gap between sustainability ideals and their practical implementation within EV interiors. Moreover, the pursuit of sustainable design must address not only lofty environmental goals but also actual consumer perceptions and preferences. Understanding how to influence consumer attitudes and behavior through innovative design is a critical pathway worthy of further development. Horn and Salvendy emphasized that product creativity significantly impacts consumer satisfaction and purchase intention [14]. Regarding technological innovation, EVs themselves are inherently technology-driven products; consequently, EV interiors often incorporate advanced technologies. Research is increasingly focusing on connecting consumer psychology with EV-related technologies, as this link is fundamental to future EV development. Jaiswal (2025), for instance, examined consumer adoption of battery electric vehicles by analyzing the relationship between technological perception, psychological response, attitude, and behavioral intention [15]. Building on this, the present study focuses on exploring EV interior design through the lens of human emotion.

2.3. Design Evaluation of Consumer Experience

This study examines consumers’ emotional responses to product design following their interaction with it. Emotion-based evaluation is particularly useful for understanding consumer tendencies in relation to vehicle interaction. Accordingly, an emotion-focused methodology was adopted to assess the appeal of EV interiors. More specifically, this study evaluates EV interior design from the perspective of design psychology. A similar study explored the affective role of future autonomous vehicle interiors using focus groups, identifying affective design attributes such as “focused,” “pleasant,” and “comfortable”, thereby demonstrating how interior design can evoke specific emotional states in users [16]. In line with this perspective, user–product interaction is viewed as a form of communication between consumers and EV interiors, mediated by emotional responses. The study focuses on assessing the emotional appeal of EV interiors as experienced by users. Key evaluation items were selected based on expert input to measure consumer perceptions of interior design. In addition, a semantic analysis method—similar to the Semantic Environment of Description (SMB)—was employed to capture experts’ subjective impressions of EV interiors. Beyond design, engineering, and marketing applications, the SMB framework has also been widely used to evaluate impressions of vehicle interiors [17]. For example, Shimizu et al. (1989) developed a simulation-based procedure to assess human impressions of car interiors, laying the groundwork for future research in this area [18].

2.4. Miryoku Engineering

Miryoku Engineering is a technical framework used to determine product attractiveness based on user preferences, incorporating insights from psychology, sociology, and aesthetics. It is widely applied to examine how product styles shaped by specific design attributes leave impressions on users. Both subjective expert interviews and objective user studies are typically conducted to explore the relationship between users’ impressions and product characteristics. In addition to identifying users’ semantic interpretations, Miryoku Engineering employs multivariate analysis to present empirical findings [19,20]. As a methodology that integrates expert knowledge with popular user perceptions, Miryoku Engineering has been widely applied across various design-related fields [21,22].

Miryoku refers to the “power of attractiveness” in the human mind and is associated with psychological concepts such as perception, sentiment, and emotion. In this study, the Japanese term Miryoku is interpreted as “appeal.” Junichiro Sanui and Masao Doi developed Miryoku Engineering based on the psychological foundations of personal construct theory [23]. Later, in 1999, Masato Sato and Gen Matsumura organized the interdisciplinary Miryoku Engineering Forum, originally launched in 1991, which aimed to examine design-related challenges and compile effective theories and methods for creating attractive products [24]. Miryoku Engineering provides a framework for defining the relationship between consumer preferences and product attributes in order to determine what constitutes appealing design.

While consumers may attempt to make rational decisions when considering whether to purchase a product, their emotional responses to merchandise cannot be overlooked in the consumption decision-making process. As a result, an increasing number of researchers have sought to examine consumer emotions alongside rational considerations. Khatoon and Rehman argued that brand-related stimuli can significantly influence consumers and evoke emotional responses during the decision-making process [25]. Their findings highlight the critical role of consumer emotion in purchasing behavior and align with the perspective of this study. Accordingly, this research applies Miryoku Engineering to investigate how various EV interior designs elicit consumers’ sustainable emotional responses.

In this section, I reviewed a broad range of research literature related to EV interior design. This study did not utilize generative artificial intelligence (GenAI) to generate text, data, or graphics, nor was GenAI used in the study’s design, data collection, analysis, or interpretation.

3. Research Objectives and Methods

3.1. Research Objectives

This study extends our previous research on car-borne central control platforms [26] by shifting the focus from a single interface to the holistic design of EV interiors. Whereas the earlier study emphasized the functional usability of control platforms, the present work investigates consumers’ emotional and perceptual responses to overall interior design. Although several features, such as “tasteful (i.e., elegant and refined),” “narrow-border screen,” and “flat and smooth style” reappear, they are reconsidered here in relation to broader spatial, aesthetic, and innovative aspects of EV interiors.

Designers of electric vehicles (EVs) aim to create attractive interiors grounded in innovative design concepts. EV manufacturers attempt to translate these creative ideas into practical interior designs that can effectively engage and motivate consumers. Beyond evaluating various design characteristics, this study explores the complex psychological considerations that influence consumers’ preferences toward EV interiors. Specifically, two critical research questions are addressed: (1) why consumers prefer EV interiors, and (2) which innovative design characteristics leave a strong impression on them. In addition, this study examines the extent to which consumer preferences vary with respect to key design attributes. To achieve this, the study integrates expert professional knowledge with general consumer responses in order to identify the most influential appeal factors and their corresponding design characteristics, using a semantic conversion framework. Furthermore, the hierarchical relationships between appeal factors and design characteristics are established. Finally, consumer responses to EV interiors are collected through a questionnaire survey and statistically analyzed using quantitative methods to determine the relative importance of each appeal factor and design element.

3.2. Research Methods

This study investigates how EV interiors evoke consumers’ emotions through various design attributes. To explore the appeal of EV interior design, Miryoku Engineering is employed as the overarching theoretical framework, utilizing two main research methods: the evaluation grid method (EGM) and Quantification Theory Type I, both of which are introduced in detail in the following sections. The research process is divided into two major phases. In the first phase, EGM is used to gather and synthesize expert perspectives on EV interiors through in-depth interviews and content analysis. The outcomes are then organized into a hierarchical diagram that visually represents the relationships between appeal factors and design elements. In the second phase, consumer responses to EV interiors are collected via a structured questionnaire and analyzed using Quantification Theory Type I. This quantitative method enables the identification and statistical evaluation of the most influential appeal factors and design characteristics from the consumers’ perspective. Both research phases are conducted under the framework of Miryoku Engineering, linking expert insights with consumer perceptions to determine the emotional appeal of EV interior design.

• Phase One: Analyzing Experts’ Concepts using EGM

This study adopt the evaluation grid method (EGM) as an analytical tool to examine semantic content derived from expert interviews and professional publications. Through this process, the appeal factors and design characteristics of EV interiors are identified and visually represented in a hierarchical diagram, illustrating the relationships between these factors and design elements. Sanui (1997) introduced two sequential procedures to integrate the Repertory Grid Method into the EGM framework [27]. This study followed these procedures to guide the research process in the first phase. Initially, trained research assistants collected descriptive terms from selected sources, including magazines, books, and online materials, in accordance with the EGM protocol. The assistants were instructed to distinguish between upper-level (abstract) and lower-level (concrete) concepts within the text and to systematically categorize and record them. Subsequently, expert interviews were conducted, in which participants were asked to compare pairs of objects and express their preferences, identifying favored and disfavored aspects of EV interiors. In addition to abstract comparisons, follow-up questions were used to elicit more specific and detailed responses. A coding system was developed to structure participants’ impressions and reasoning, transforming their semantic input into a graphical hierarchical structure. The goal of this system is to connect participants’ abstract impressions with their concrete explanations, following the principles of the EGM, which has been widely applied in various design-related fields [28,29].

In this phase, the objective was to obtain professional insights from participants with relevant expertise in EV interior design. Instead of relying on simple multiple-choice questions, in-depth interviews supported by content analysis were employed to collect richer qualitative data. The expert knowledge gathered through these methods had to be systematically interpreted and synthesized. Therefore, the evaluation grid method (EGM) was selected as an appropriate approach for evaluating EV interiors from an expert perspective in this phase. The results of this stage are presented using interpretive structural modeling to visualize the relationships between key concepts. A similar approach was adopted by Dong (2010), whose findings offer a useful reference for this study [29]. In this research, the EGM was used to identify the appeal factors and specific design characteristics of EV interiors, and the results are visualized through a hierarchical diagram. The detailed procedures are described as follows:

First, three research assistants were recruited and trained to conduct content analysis and in-depth interviews. They were instructed on how to identify specific phrases and abstract emotional vocabulary. More specifically, the assistants collected expert-generated descriptions related to EV interiors and were trained to distinguish between technical terms (e.g., professional nouns) and emotional expressions (e.g., adjectives), in accordance with the principles of the evaluation grid method (EGM).

Second, the research assistants collected authoritative sources related to EV interior design, such as automotive magazines, online blogs, and expert columns, to conduct content analysis. This analysis aimed to identify and present the basic semantic relationships among the collected words and phrases.

Third, the research assistants selected and interviewed experts with substantial knowledge of EV interiors. The group included four male and three female experts, ranging in age from 29 to 58. Two of the experts were editors of automotive magazines, three were experienced sales professionals, and the remaining two served as senior managers in the design departments of automobile manufacturers. A total of 53 sample cards featuring images that represented key characteristics of EV interiors were prepared and used during the interviews. All participating experts had at least 25 years of experience in vehicle-related fields, meeting the eligibility criteria for this study, which required extensive professional backgrounds in automotive design.

Fourth, the research assistants conducted one-on-one interviews, allowing each expert to express their preferences regarding EV interiors during a one-hour session. Each of the seven experts was then guided to sort the 53 sample cards into three groups, based on the strength of their preference—from strong to weak—at different intervals during the session. Furthermore, the assistants asked follow-up questions to elicit the experts’ reasoning behind their groupings, enabling the study to gather qualitative insights into their judgments of EV interior characteristics.

Fifth, the evaluation grid method (EGM) was applied to organize the results of the content analysis and in-depth interviews, identifying the appeal factors and specific characteristics of EV interiors based on the experts’ professional descriptions and reasoning. Through this process, a total of 233 emotional words and descriptive phrases related to EV interiors were collected. Using the EGM framework, these terms were categorized into “upper-level” and “lower-level” concepts. Descriptive phrases that were more specific and technical were classified as lower-level concepts, while more abstract emotional words, such as fashionable, were assigned to the upper-level category. Finally, the original evaluation items were derived by converging similar upper-level concepts and merging related emotional expressions.

All of the aforementioned procedures were carried out to identify the appeal factors and specific design characteristics of EV interiors using the evaluation grid method (EGM). The results of the EGM were then organized and visualized through a hierarchical diagram. Based on these findings, key evaluation items were selected for use in the questionnaire survey conducted in the next phase of the study. All the steps carried out in the EGM are presented in Figure 1.

• Phase two: Evaluating Consumer Responses Using Quantification Theory Type I

Compared to the first phase, which explored expert perspectives on EV interiors and identified evaluation items through semantic analysis, the second phase of this study investigated general consumers’ preferences using Quantification Theory Type I (QTT1), presenting the corresponding statistical results. Specifically, the key “upper-level” and “lower-level” concepts derived from the EGM analysis in the first phase were used as evaluation items in the consumer questionnaire. The relationships among these variables were analyzed using a form of multiple linear regression based on the questionnaire data [30]. QTT1 was employed to measure the strength of the associations between design characteristics and stylistic impressions. In this framework, the weights assigned to each evaluation item reflect the degree of consumer preference for specific design features [31]. In this way, consumers’ emotional tendencies toward EV interiors can be quantified in a statistically meaningful manner using the QTT1 method.

Evaluation items with higher frequencies in the EGM analysis—those most frequently favored by experts—were selected as the basis for the questionnaire content. In addition, the hierarchical structure derived from the EGM informed the organization of the questionnaire, which was designed to assess general consumers’ emotional responses to EV interiors. Specifically, the questionnaire was structured into three levels of evaluation items: “original,” “upper-level,” and “lower-level,” progressing from abstract concepts to specific attributes. After collecting all valid responses, Quantification Theory Type I was applied to statistically analyze the data and quantify consumer preferences. Through this process, the key impressions influenced by specific design characteristics of EV interiors were identified. Furthermore, the EGM-based questionnaire design helped to ensure that the questions were concise and easy to understand, allowing respondents to provide effective and meaningful answers. The key attributes and categories of EV interiors were used to form the foundation of the questionnaire, based on their influence on consumer impressions.

The questionnaire survey was designed to collect general consumers’ impressions of EV interiors both extensively and accurately. To ensure efficiency in responses, the study employed purposive sampling, allowing respondents to recommend potential participants who met the research criteria. This approach enabled continuous recruitment of qualified participants through referrals, effectively expanding the sample size while maintaining reliability during the data collection process. Only consumers who currently owned or had previous experience with an EV were included in the sample, while those with no EV experience were excluded to enhance the validity of the results. A total of 455 questionnaires were distributed to eligible participants, and 332 were returned. After excluding 27 responses due to either extreme values or insufficient EV experience, 305 valid questionnaires were retained for analysis. The final dataset, representing a valid response rate of 67%, consisted of 157 male and 148 female respondents, ranging in age from 19 to 63. The data were analyzed using Quantification Theory Type I to evaluate consumer preferences related to EV interior design. All the procedures of QTTI are presented in Figure 2.

All procedures used in this study are presented in Figure 3.

4. Analysis and Results

4.1. Evaluating Experts’ Impressions Using EGM

This study applied the evaluation grid method (EGM) to synthesize experts’ impressions of EV interiors, presenting the results through a hierarchical diagram. This hierarchical structure summarized the viewpoints of all experts and categorized the content into three levels: original evaluation items, emotional impressions (upper-level), and specific design characteristics (lower-level). Emotional adjectives were distinguished from specific nouns to support this classification. An example of an individual participant’s evaluation structure is shown in Figure 4. Figure 5 presents the overall EGM results, which identify consumers’ preferences based on the key appeal factors and characteristics of EV interiors as perceived by all experts. The complete list of evaluation items, including critical upper-level and lower-level concepts, is also presented in Figure 3. These evaluation items served as benchmarks for assessing consumer preferences and were subsequently converted into questionnaire items. The selected items formed the foundation of the survey used to investigate consumer impressions. Additionally, the more frequently an evaluation item appeared in expert interviews, the more likely it was to be selected for inclusion in the questionnaire. The evaluation items ranked by frequency of mention are presented in

Table 1. Ranking of evaluation items by frequency in the hierarchical diagram.

Original Images	Upper Level (Reasons)	Lower Level (Specific Attributes)
Technical innovation, 24	Tech-laden, 22	Ambient lighting, 18
Tasteful, 22	Sophisticated, 19	Additional decoration, 15
Avant-garde, 21	Modern, 20	Mirror texture, 19
Sustainable innovation, 19	Energy-saving, 16 Eco-friendly, 16	Recycled material, 17 Natural fibers, 14

.

This hierarchical diagram, constructed using the evaluation grid method (EGM), represents the aggregated preferences of all seven expert participants. The numbers shown on the right side of each item indicate how many times the same opinion was expressed across the expert responses.

The four most important original evaluation items—“tasteful,” “avant-garde,” “technical innovation,” and “sustainable innovation”—were identified through the EGM process and selected as the foundation for the main sections of the questionnaire survey.

• The first original evaluation item, “tasteful,” is associated with two upper-level concepts: “sophisticated” and “elegant.” These, in turn, correspond to four lower-level design features: “additional decoration,” “narrow-border screen,” “high-quality leather or Alcantara,” and “flat and smooth style.”
• The second item, “avant-garde,” is linked to “modern” and “virtualized” as upper-level concepts, which relate to six lower-level features: “mirror texture,” “glass texture,” “large touchscreen,” “portrait-oriented touchscreen,” “multiple-screen displays,” and “roof-mounted cinema screen”.
• The third item, “technical innovation,” includes “tech-laden” and “revolutionary” as upper-level categories, which are connected to five lower-level features: “ambient lighting,” “metal texture,” “push-type electronic door,” “advanced digital instrument cluster,” and “special gear device”.
• The fourth item, “sustainable innovation,” consists of three upper-level concepts: “energy-saving,” “eco-friendly,” and “alternative thinking”. These are associated with six lower-level features: “recycled materials,” “plant-based leather,” “natural fibers like bamboo or hemp for upholstery,” “lightweight materials,” “leather-free texture,” and “innovative production processes”.

Table 2. Top four original evaluation items and their associated reasons, ranked by frequency in the hierarchical diagram.

Classified	Original Images	Reasons (Upper Level)
First	Technical innovation, 24	Tech-laden, 22 Revolutionary, 20
Second	Tasteful, 22	Sophisticated, 19 Elegant, 18
Third	Avant-garde, 21	Modern, 20 Virtualized, 19
Forth	Sustainable innovation, 19	Energy-saving, 16 Eco-friendly, 16 Alternative thinking, 15

presents the top four original evaluation items and their corresponding design features, selected from the EGM hierarchical diagram based on their frequency of appearance across expert interviews.

4.2. Quantification Theory Type I Analysis for Surveying Consumers’ Reactions

After the critical evaluation items were identified through expert analysis, the questionnaire was developed using the level-based structure derived from the EGM results (see

Table 3. Level-based structure of the questionnaire derived from EGM. Adapted from Ref. [26].

Level of Questionnaire	First Level	Second Level	Third Level
Type of question	Original evaluation item	Upper level	Lower level
Example of question	Avant-garde	Modern	Mirror texture

). The weights of these evaluation items for EV interiors were then measured based on consumer responses using Quantification Theory Type I. The statistical analysis involved several procedural steps. Specifically, the formulas used in Quantification Theory Type I were implemented in an Excel Macro for efficient data processing. The results of the analysis are presented in

Table 4. Partial correlation coefficients, category scores, and coefficient of determination for the factor “tasteful.” Adapted from Ref. [26], under CC BY 4.0 license.

	Categories	Category Scores	Partial Correlation Coefficients
Sophisticated	Additional decoration	−0.043	0.389
	Narrow-border screen	0.086
Elegant	High-quality leather or Alcantara	−0.137	0.666
	Flat and smooth style	0.121
C	0.750
R=	0.666
R2=	0.443

,

Table 5. Partial correlation coefficients, category scores, and coefficient of determination for the factor “avant-garde” Adapted from Ref. [26], under CC BY 4.0 license.

Items	Categories	Category Scores	Partial Correlation Coefficients
Modern	Mirror texture	−0.053	0.430
	Glass texture	0.092
Virtualized	Large touchscreen	−0.135	0.648
	Portrait-oriented touchscreen	0.115
	Multiple-screen displays	* 0.167
	Roof-mounted cinema screen	0.042
C	0.76
R=	0.649
R2=	0.421

* This asterisk indicates the category with the highest score.

,

Table 6. Partial correlation coefficients, category scores, and coefficient of determination for the Factor “technical innovation.” Adapted from Ref. [26], under CC BY 4.0 license.

Items	Categories	Category Scores	Partial Correlation Coefficients
Tech-laden	Ambient lighting	−0.040	0.392
	Metal textures	0.089
Revolutionary	Push-type electronic door	−0.141	0.666
	Advanced digital instrument cluster	0.118
	Special gear device	0.040
C	0.750
R=	0.666
R2=	0.443

and

Table 7. Partial correlation coefficients, category scores, and coefficient of determination for the factor “sustainable innovation.” Adapted from Ref. [26], under CC BY 4.0 license.

Items	Categories	Category Scores	Partial Correlation Coefficients
Energy-saving	Recycled material	−0.042	0.372
	Plant-based leather	0.083
Eco-friendly	Natural fibers like bamboo or hemp for upholstery	−0.133	0.626
	Lightweight materials	0.117
Alternative thinking	Leather-free textures	0.008	0.074
	Innovative production processes	−0.013
C	0.750
R=	0.668
R2=	0.446

, which assess the factors of “tasteful,” “avant-garde,” “technical innovation,” and “sustainable innovation”. These factors were evaluated based on the coefficient of determination, partial correlation coefficients, and category scores.

In this study, Quantification Theory Type I was used to quantify the importance of the original evaluation items by measuring their coefficients of determination. A higher coefficient of determination indicates greater reliability and persuasiveness of the findings. The reliability test showed that all four original evaluation items had a significant influence on EV interiors, as their coefficients of determination exceeded 0.6. This result suggests that the four original evaluation items shaped consumers’ impressions through their corresponding upper-level factors, which can be regarded as indicators of preference for EV interiors. For example, the coefficient of determination (R² = 0.668) for the factor sustainable innovation demonstrated high reliability, according to the Quantification Theory Type I analysis (Table 7).

Partial correlation coefficients were used as test values to determine the strength of the relationships between the upper-level evaluation items and the corresponding factors. Higher partial correlation coefficients indicate stronger upper-level evaluation items. For instance, the finding that the revolutionary concept had the highest partial correlation coefficient (0.666) suggests that consumers’ impressions of technical innovation were most influenced by this upper-level attribute (Table 6).

The category score values indicate the relative importance of each evaluation item. Higher category scores suggest that the corresponding design characteristic plays a more significant role in its associated upper-level reason. For example, the finding that the design characteristic multiple-screen displays received a higher score indicates that this lower-level category has a positive influence on the virtualized upper-level reason (Table 5). Conversely, negative category scores indicate that a design characteristic may have an adverse influence on its corresponding upper-level reason. For instance, the result showing that consumers assigned the category high-quality leather or Alcantara a negative score suggests that this design characteristic could negatively affect the elegant reason (Table 4).

The analysis of the coefficients of determination confirmed that EV interiors convey consumer impressions of tasteful, avant-garde, technical innovation, and sustainable innovation. Regarding the tasteful factor, the statistical results show that consumers preferred the elegant feature (0.666) over sophisticated (0.389), as indicated by the partial correlation coefficients (Table 4). Furthermore, according to the category scores (0.121), consumers favored the design characteristic flat and smooth style, which had a stronger influence on their impression of the elegant feature. The pronounced influence of flat and smooth style on the elegant impression may be explained by several psychological mechanisms. From the perspective of processing fluency, smooth and simplified forms are processed more easily and thus perceived as more aesthetically pleasing and elegant [32]. Additionally, minimalist aesthetics—characterized by clarity, simplicity, and visual restraint—have been shown to heighten perceptions of elegance, usability, and professional credibility. Finally, material aesthetics research indicates that smooth textures are consistently associated with sophistication and elegance, reinforcing the present findings that flat and smooth style enhances the perception of elegance [32].

Regarding the “avant-grade” factor, compared to the “modern” factor (0.343), consumers put more emphasis on the “virtualized” (0.648) concept because of the design characteristic of “multiple-screen displays” based on the higher category scores (0.167). Regarding the “technical innovation” factor, compared to “tech-laden,” consumers viewed “revolutionary” (0.666) as the priority reason according to the partial correlation coefficient test. The design characteristic of “advanced digital instrument cluster” (0.118) may play a critical role in affecting consumers’ impressions of the “revolutionary” factor based on the category scores. While direct research connecting advanced digital instrument clusters with impressions of the “revolutionary” factor is limited, related design research indicates that digital clusters—by enabling intuitive, graphical, and user-centered interfaces—substantially elevate aesthetic quality and operational experience, reinforcing perceptions of innovation [33]. This aligns conceptually with our finding that such clusters contribute strongly to EV consumers’ impressions of the “revolutionary” factor.

Regarding the sustainable innovation factor, the statistical results show that eco-friendly (0.626) was the most favored among the three reasons and had a significant influence on the impression of sustainable innovation. The finding that “eco-friendly” features significantly influence perceptions of sustainable innovation is supported by the broader literature. For instance, Cheng et al. (2023) demonstrated that green process innovations and productivity improve overall sustainability, particularly when environmental awareness is high [34]. Similarly, Adomako and Nguyen (2023) showed that eco-innovation, fostered by strong stakeholder relationships, mediated improved product performance and supported sustainable innovation outcomes [35]. These studies reinforce the role of eco-friendly design in shaping consumer impressions of sustainable innovation.

These four factors collectively explain why consumers prefer EV interiors and identify the specific characteristics that lead them to choose particular interior designs, based on the results of the Quantification Theory Type I analysis presented in this section.

5. Discussion

The results of the EGM, summarized in the hierarchical diagram (Figure 2), reveal the most representative appeal factors, the reasons for consumers’ preferences, and the key design characteristics of EV interiors from the experts’ perspectives. Building on this, a questionnaire survey was conducted—based on the experts’ findings—to investigate general consumer preferences for EV interior design. The analysis identified four appeal factors—tasteful, avant-garde, technical innovation, and sustainable innovation—as playing critical roles in shaping consumer preferences. Among these, innovation emerged as the central driver of EV interior appeal. While technical innovation and sustainable innovation rely heavily on creativity to capture consumer interest, the factors of tasteful and avant-garde require designers’ meticulous attention to detail to create interiors that are both aesthetically pleasing and emotionally engaging. By examining EV interiors through the lens of innovation, this study provides insights into how the design of electric vehicles can be distinguished from that of traditional fuel-powered vehicles, offering consumers experiences that go beyond functional requirements to inspire lasting impressions.

The analysis of the coefficients of determination confirmed that EV interiors convey consumer impressions of tasteful, avant-garde, technical innovation, and sustainable innovation. Regarding the tasteful factor, consumers preferred the elegant feature (0.666) over sophisticated (0.389), as indicated by the partial correlation coefficients (Table 4). According to the category scores (0.121), the design characteristic of flat and smooth style had the strongest influence on the impression of the elegant feature. Figure 6 shows a seamless large-arc display merging multiple screens under a single glass surface, exemplifying a minimalist yet revolutionary user interface. Overall, EV interiors were perceived as tasteful primarily due to the elegant attribute, as supported by the partial correlation coefficient analysis. The flat and smooth Style characteristic was found to significantly enhance this perception. These findings indicate that consumers’ preferences are shaped by specific styles that align with their aesthetic and emotional expectations—preferences that extend beyond the basic functional demands of driving.

Regarding the avant-garde factor, consumers placed greater emphasis on the virtualized concept (0.648) than on the modern concept (0.343), primarily due to the design characteristic of multiple-screen displays, which had the highest category score (0.167) for this factor (Table 5). The partial correlation coefficients indicate that the virtualized concept significantly shaped consumers’ impressions of the avant-garde factor. Furthermore, multiple-screen displays had the strongest influence on the virtualized attribute compared to other design characteristics of EV interiors. These results highlight the importance of virtualization in automotive interior design. In this study, the term virtualized refers to transforming physical controls or displays inside (or outside) a vehicle into touchscreens for more convenient driver monitoring and control. Compared to ICEVs, which provide drivers with numerous physical interfaces for vehicle control, EVs adopt virtualized interfaces, such as touchscreens, which enable drivers to monitor and operate the vehicle. Figure 7 exemplifies the flat and smooth style evaluated in this study and illustrates the contemporary shift toward touchscreen-centric EV interiors. The touchscreen design not only had a strong impact on consumers’ avant-garde impressions but also symbolized a future trend in EV interiors. This finding further suggests that consumers value functional innovations that can enhance their adoption of EVs [13]. Although the touchscreen remains a critical component in current EV interior design, it still relies heavily on direct driver operation. Looking ahead, artificial intelligence (AI) is likely to reshape EV interiors by enabling personalized, adaptive, and context-aware user experiences. AI-driven systems can adjust lighting, temperature, and interface layouts based on real-time user behavior, thereby enhancing the perception of innovation. Consequently, the role of the touchscreen is likely to evolve as AI-driven systems become more prevalent.

Regarding the technical innovation factor, consumers prioritized the revolutionary factor (0.666) over the tech-laden factor, as reflected in the partial correlation coefficients (Table 6). The design characteristic of advanced digital instrument cluster (0.118) played a critical role in shaping the impression of the revolutionary concept. Figure 8 illustrates the advanced digital interface characteristic. This suggests that consumers’ perceptions of technical innovation were strongly tied to the revolutionary attribute, with the advanced digital instrument cluster making a substantial contribution to this impression. These findings indicate that advanced technology plays a pivotal role in EV interior design. EV interiors rely heavily on technological innovations to enhance appeal, and more technical features, such as push-type electronic doors, could be integrated to further strengthen this perception. In fact, the design of push-type electronic doors is rarely seen in ICEVs, most of which are still equipped with traditional handles. Beyond push-type electronic doors, other EV-specific designs, such as special gear devices, reflect different considerations compared to ICEVs, which tend to emphasize human habits more than technical innovations. This result underscores the importance of new technology in shaping consumer impressions and aligns with the findings of Shahab et al. [24], as well as the established links among technology, psychology, perception, attitude, and intention [16].

Regarding the sustainable innovation factor, the statistical results show that the eco-friendly feature (0.626) was the most favored among the three upper-level reasons and had a significant influence on the overall impression of sustainable innovation (Table 7). Figure 9 highlights the brand’s eco-friendly approach to integrating recycled materials into EV interiors, including the use of recycled textiles, such as repurposed blue denim fibers. This indicates that the eco-friendly attribute played a central role in shaping consumers’ perceptions of sustainability in EV interiors. In addition, the design characteristic of lightweight materials was particularly well-received, reinforcing the impression of sustainable innovation among general consumers. These findings suggest that consumers’ sustainability needs can be effectively addressed through innovative approaches, such as the use of plant-based leather. Compared to ICEV designs, which typically develop car interiors with a focus on cost-effectiveness, EVs can offer consumers more sustainable options and motivate them through innovations, as evidenced by the results of this study.

Collectively, these findings explain why consumers prefer EV interiors and identify the specific design characteristics that most strongly influence their preferences, as revealed by the Quantification Theory Type I analysis. The four upper-level reasons—elegant, virtualized, revolutionary, and eco-friendly—were shown to contribute most significantly to the impressions of tasteful, avant-garde, technical innovation, and sustainable innovation, respectively. In addition, the corresponding key design characteristics—flat and smooth style, multiple-screen displays, and advanced digital instrument cluster—emerged as critical elements for creating EV interiors that align with consumer preferences. Furthermore, these evaluation items collectively reinforce the overarching impression of innovation. This result supports the argument that creativity plays a critical role in driving consumer satisfaction and purchase intentions [15]. The study also indicates that consumers increasingly prioritize long-term value beyond immediate functional needs, suggesting that a product’s perceived value can significantly influence purchase intentions [14]. In addition, the results of this study highlight the most significant differences between EVs and ICEVs and point out the complexities of EV purchase decisions [36].

6. Conclusions

6.1. Implications

This study examined electric vehicle (EV) interior design from the perspective of consumer emotions, emphasizing the role of innovation in shaping preferences. Drawing on Miryoku Engineering, this research integrated expert evaluations with consumer surveys to identify the most influential appeal factors—tasteful, avant-garde, technical innovation, and sustainable innovation—and their corresponding design characteristics. These findings reveal that innovative design is central to enhancing the desirability of EV interiors, distinguishing them from those of traditional internal combustion engine vehicles (ICEVs).

From a practical perspective, the results offer actionable guidance for EV designers and manufacturers. Beyond “technical innovation” and “sustainable innovation,” which rely heavily on creativity to appeal to consumers, factors such as “tasteful” and “avant-garde” also require deliberate, detail-oriented design to capture attention and stimulate purchase intent. While interior design significantly influences consumer preference, it should be complemented by equally innovative approaches in exterior styling and marketing strategies.

In an era of rapidly advancing technology and increasing prevalence of AI applications, this technological horizon suggests that future EV interior design will not only emphasize physical and digital integration, but also address ethical considerations such as privacy, user dependency, and transparency. Acknowledging these opportunities and challenges ensures that sustainable innovation in EV interiors remains both forward-looking and responsible.

In addition, marketing designs—particularly those targeting consumer psychology—can further reinforce purchase motivations. Therefore, integrating online and offline promotional strategies that evoke emotional resonance should be a strategic priority. Given the competitive landscape with ICEVs, creating lasting value in the minds of EV consumers remains essential.

From a theoretical perspective, this study contributes to the interdisciplinary understanding of EV interior design by applying Miryoku Engineering to measure the interaction between human emotions and vehicle interiors. It demonstrates that design evaluation can effectively capture consumers’ emotional and cognitive responses to specific stylistic and functional attributes. In addition, the limitations, contributions, and directions for future research of this study are outlined below for further explanation.

6.2. Limitations

Certain limitations must be acknowledged in this study. For instance, consumers’ perceptions of an interior may change due to varying environmental conditions while a vehicle is in motion. Additionally, the interpretation of evaluation items collected via the evaluation grid method (EGM) may be influenced by linguistic or cultural differences among participants.

The second limitation of this study is that the initial evaluation items were derived from expert interviews, which may inevitably reflect subjective biases based on professional backgrounds. To address this concern, we employed a mixed-method approach: the expert-derived constructs were subsequently validated through a large-scale consumer survey analyzed using Quantification Theory Type I. This methodological triangulation reduced the potential impact of expert bias and ensured that the findings captured both professional insights and general consumer perspectives. Moreover, the experts consulted in this study came from diverse backgrounds, including automotive editors, sales professionals, and design managers, which further reduced the risk of bias caused by relying on a small, homogeneous group of experts.

Furthermore, although the evaluation grid method (EGM) is qualitative in nature, we mitigated potential bias by systematically validating the constructs in a large-scale consumer survey (305 valid responses). The data were analyzed using Quantification Theory Type I, which ensured statistical rigor and reliability, as evidenced by coefficients of determination exceeding 0.6. This integration of qualitative and quantitative approaches strengthens the credibility of the findings.

The third limitation of this study is that, although the sample size was acceptable for the analysis, all participants were drawn from a single cultural and national context. Perceptions of design characteristics, such as elegance, innovation, or eco-friendliness, are known to vary across demographic groups and cultural settings. As a result, the findings may not fully capture cross-cultural differences in consumer perceptions of EV interiors. Additionally, the conclusions reported here should be interpreted with caution when applied to different populations.

The fourth limitation of this study is that, while the evaluation grid method (EGM) and Quantification Theory Type I (QTTI) provided useful insights into the relationship between consumers’ impressions and EV interior characteristics, these approaches rely primarily on self-reported and semantic responses. In addition, the reported R² values and partial correlation coefficients serve as indicators of effect size in Quantification Theory Type I analysis. As such, their reliability and validity in capturing immediate emotional reactions may be limited

6.3. Contributions

While both the EGM and Quantification Theory Type I are established tools, their combined application within the framework of Miryoku Engineering to explore EV interior design represents a novel methodological integration. This approach allows for a systematic translation of expert impressions into quantifiable consumer preferences, bridging qualitative and quantitative insights. Thus, the novelty of this research lies not in the invention of new methods, but in the innovative application of existing tools to reveal how consumers perceive innovation in EV interiors—a topic that remains largely underexplored in the current literature.

This study also recognizes that EV purchasing decisions are becoming increasingly complex [34], driven by a combination of technological, economic, and policy factors. This complexity underscores the need to examine EV adoption from multiple perspectives. By focusing on interior design, this research addresses essential intersections among psychology, design, and human–machine interaction. The insights provided herein can serve as a reference for researchers, automotive designers, and industry practitioners seeking to create interiors that not only satisfy functional requirements but also inspire emotional engagement.

6.4. Future Studies

Finally, the study aspires to advance sustainability goals by encouraging design innovations that align with environmental protection and societal well-being. Future research will further explore how innovative marketing strategies, grounded in emotional appeal, can enhance consumer adoption, while continuing to investigate ways to integrate technological and aesthetic innovations with sustainable design principles.

Future research should extend this work by incorporating cross-cultural and cross-demographic samples in order to validate the robustness and universality of the proposed relationships.

Future research can also strengthen the measurements by combining these techniques (EGM and QTTI) with standardized affective scales (e.g., PAD, PANAS) or physiological methods, such as eye-tracking, galvanic skin response, or heart rate variability, thereby providing a more robust assessment of emotional responses to EV interior design.

In summary, this study extends the understanding of EV interior design by highlighting the innovative characteristics that most strongly shape consumer perceptions and emotions. By integrating expert evaluations with consumer surveys through Miryoku Engineering, EGM, and Quantification Theory Type I, this research offers a novel methodological approach to exploring design psychology in EV contexts. The findings identify four critical appeal factors—tasteful, avant-garde, technical innovation, and sustainable innovation—and link them with concrete design elements. These insights contribute to both theoretical knowledge in design and human–vehicle interaction and practical guidance for designers and manufacturers, supporting the development of user-centered and sustainable EV interiors.