Electric Kettles: An Assessment of Energy-Saving Potentials for Policy Making in the European Union
2. Definition of Representative Kettles for the EU-27 Market
2.1. Common Kettle Technologies
- A container filled with water where the actual heating and boiling takes place. It is usually equipped with a handle and a lid and offers additional room for sensors and the control system. The container can differ in construction design (single-wall, double-wall, insulated, and vacuum), material (plastic, steel, and glass), capacity, and included features (e.g., water-level indicator, filters, etc.);
- Cordless models are portable as they feature a base that is connected to the mains;
- A power cord with a plug;
- A heating element. This can be an immersed element in direct contact with the water or an underfloor element concealed in the bottom of the container. The types of elements are as follows:
- Common tubular heating element: This consists of a heating wire (as the original resistance heating element), often comprising a nickel-based, nichrome heating element (NiCr), magnesium oxide powder, and an outer casing;
- A thick film heating element, which generally consists of a metal core. The core is coated with a glass-ceramic lining, which ensures electrical insulation and carries conductive, screen-printed heater tracks. These elements can transfer a higher amount of energy/heat per surface. Additionally, such elements offer a lower thermal mass; therefore, heat losses to the surrounding material are lower. Currently, thick film heating elements are more expensive than conventional, tubular ones. Kettles with thick film heating element are very rare on the EU market.
- Sensors, control units, and mechanical or electrical switches that ensure the proper function of the kettle with features such as auto-switch-off, temperature selection, keep-warm, and boil-dry protection (i.e., precaution against empty operation). Temperature control is based on the following main technologies:
- Bi-metal switches: Steam from the boiling water is conducted to a mechanical bi-metallic disk in the base, handle, or lid. When the steam reaches a defined temperature, the bi-metallic disk snaps its position and cuts off the power. Bi-metal switches have tolerances of +/− 5 to 7 K.
- Thermistors: Electric elements that change their electrical resistance in response to a change in temperature. Kettles use Positive Temperature Coefficient (PTC) models typically chosen for several pre-set temperatures (step-approach) or Negative Temperature Coefficient (NTC) models with step or stepless temperature setting.
- Both NTCs and PTCs can provide features such as auto-switch-off, boil-dry (PTC), temperature selection, and keep-warm and are more accurate than bi-metal switches.
2.2. Overview of the Market in the EU-27
2.3. Utilisation of Kettles
2.4. Definition of Representative Kettles
3. Characterisation of the Base Cases
3.1. Existing Test Standards and Energy Efficiency Metrics
3.2. Measurement Method
- For kettles with pre-set temperature: energy consumption and time measurement for heating until shut-off at a pre-set temperature of 70 °C (or the nearest pre-set temperature above 70 °C) at minimum water capacity;
- For kettles with keep-warm feature: average input power, average water temperature, and maximum keep-warm time measurement for the keep-warm function at the maximum keep-warm temperature, and maximum time setting at a rated water capacity. In addition: temperature drop during a cool-down phase of 30 min after boiling at rated water capacity.
3.3. Measurement Results
3.3.1. Specific Consumption for Heating
3.3.2. Keep-Warm and Cool-Down Measurements
3.4. Performance of the Representative Kettles
4. Energy-Saving Potentials
4.1. Overview of the Measures
- Indicator: This measures aims to reduce “overboiling”, which has a significant effect on energy consumption, by directly showing the user how much water is in the kettle. This is carried out using an enlarged water level indicator down to a low minimum volume (e.g., 0.25 l) and information on the filling level in both litres and cups.
- Heating: In this design option, conventional heating elements (immersed or concealed) are replaced by thick film heating elements. Thick film heating elements operate with higher efficiency due to their higher energy density and lower thermal losses, which has a particularly strong effect on performance in the case of low filling levels.
- Electronics: Measurements reveal an “overheating” of kettles, i.e., a situation where kettles exceed the boiling temperature beyond 95 °C as required by the current standard IEC 60530:1975 . This measure seeks to reduce overheating by automatically shutting off the heating early by sensors and controllers with greater accuracy.
- Insulation: To minimise energy dissipation after boiling, this measure improves kettle insulation with a double-shell container. This has special relevance for keep-warm features but also reduces heat losses in general during the cooling phase, i.e., after boiling.
- Temperature: In some cases, e.g., preparing certain types of tea, temperatures of 95 °C or above are not required. This measure allows temperatures below 95 °C to be selected.
- Keep-warm: Currently, this measure is intended to limit the use of the keep-warm function when this is available. Excessive re-heating of boiled water is avoided by setting a maximum duration for keep-warm to 30 min.
4.2. Data and Assumptions
4.3. Analysis of Impact
4.4. Analysis of Packages
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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|General||Description||Unit||BC 1||BC 2||BC 3|
|Description||Concealed heating element||No||Yes||Yes|
|Real input power||[W]||1000||2200||2200|
|Maximum volume (Vmax)||[l]||1.0||1.7||1.7|
|Minimum volume (Vmin)||[l]||0.50||0.50||0.50|
|Sales||Market share in 2020||%||15%||79%||6%|
|Name/Reference||Description||Country||Volume [l]||Start–End Water Temperature [°C]||Energy Efficiency Metric||Detail|
|IEC 60530:1975 ||Test standard||1||15–95||None (focus on boiling time)|
|Blue Angel/RAL-UZ 133 ||Eco label (voluntary endorsement label)||Germany||1||20–100 (switch off)||Specific energy consumption [kWh/l] |
W20 = WM × 80/TM
|WM: power consumption until automatic switch-off of the kettle |
Temperature difference compared to the boiling temperature of 100 °C
|Topten ||Voluntary endorsement label (private initiative)||Switzerland||1||15–100 (switch off)||Yearly energy consumption [kWh/a] |
Ekettle = Eboil + Ekeepwarm + Estand-by
|Eboil = 365 × Econsumption to heat 1 l |
if T-setting feature is available: −10%
Ekeep warm = Pkeep warm × 0.5 × (max time keep-warm) × 365 ll
if no measurement possible: 15 W × 1 h × 365
Estand-by: Pstand-by × 8760 h
|Eco-Label Standard (EL408:2013) ||Voluntary endorsement label||South Korea||1||15–99||Specific energy consumption [kWh/l]|
|GB/T 22089-2008 ||Voluntary standard||China||Rated volume||20 *–80||η = C × M × (80−T1)/E × 100%||T1: start temperature|
|Greenmark N126 ||Voluntary endorsement label||Taiwan||1||15–99||Specific energy consumption [kWh/l]|
|Energy Efficiency Label ||Voluntary comparative label||Thailand||30–90||η = ϱ × (90−30)/(0.24 P × t) × 100|
|ISIRI 7875 ||MEPS and Energy Label||Iran||1||20–90||Specific energy consumption [kWh/l]|
|Manufacturer (confidential)||Test method applied by a manufacturer||20–98||Efficiency: |
η = Q/Energy Consumption
Q = (98−20) × 4186 × Volume
|Test||Type of Test||Quantity of Water||Measurement||Measured or Calculated Parameters|
|1||Heating 80 K||Rated water capacity||Until shut-off (at least +80 K)||E95°C,Vrated, t95°C,Vrated, EEI|
|2||Heating 80 K||Minimum water capacity||Until shut-off (at least +80 K)||E95°C,Vmin, t95°C,Vmin|
|3||Heating 80 K||1 l *||Until shut-off (at least +80 K)||E95°C,1, t95°C,1|
|4||Heating||Rated water capacity||Until shut-off, when 70 °C pre-set temperature (or the nearest pre-set temperature above 70 °C) is selected||E70°C,Vrated, t70°C,Vrated|
|5||Heating||Minimum water capacity||Until shut-off, when 70 °C pre-set temperature (or the nearest pre-set temperature above 70 °C) is selected||E70°C,Vmin, t70°C,Vmin|
|6||Keep-warm||Rated water capacity||Max keep-warm temperature selected|
Longest possible keep-warm time
|tkwmax, Tkw, Pkw,Vrated, pkw,Vrated|
|7||Cool down||Rated water capacity||Tdrop|
|8||Standby||0 l||According to current harmonised standard||Pstandby|
|9||Durability||1 l (or Vrated if Vrated > 1 l)||Until shut-off (at least +80 K)||Ncyc|
|Description||Unit||BC 1||BC 2||BC 3|
|Description||Capacity of the container [l]||1.0||1.7||1.7|
|Real input power [W]||1000||2200||2200|
|Technical data Performance||Lifetime||[a]||6||6||6|
|Maximum volume (Vmax)||[l]||1.0||1.7||1.7|
|Minimum volume (Vmin)||[l]||0.50||0.50||0.50|
|Heat 1 l from 15 °C to 98 °C (Tswitchoff)||time to heat [s]||390||189||189|
|Heat Vmax from 15 °C to 98 °C (Tswitchoff)||time to heat [s]||390||306||306|
|Heat Vmin from 15 °C to 98 °C (Tswitchoff)||time to heat [s]||213||103||103|
|Heat 1 l from 15 °C to 80 °C||time to heat [s]||n.a.||n.a.||148|
|Vmax from 15 °C to 80 °C||time to heat [s]||n.a.||n.a.||240|
|Keep-warm: max time||[min]||n.a.||n.a.||60.0|
|Keep-warm 1 l at 98 °C||[kW/l]||n.a.||n.a.||0.127|
|Keep-warm 1 l at 90 °C||[kW/l]||n.a.||n.a.||0.115|
|Keep warm 1 l at 80 °C||[kW/l]||n.a.||n.a.||0.099|
|Yearly energy consumption||Heating (assuming 1 l at Tmax each time) – indicative||[kWh/a]||86.75||92.19||92.19|
|Heating (assuming 1 l filled in and 73% at 98 °C, 22% at 90 °C, and 5% at 80 °C)||[kWh/a]||86.75||92.19||88.99|
|Keep-warm (assuming 1 l at 98 °C over 60 min every day)||[kWh/a]||-||-||46.25|
|Total energy consumption [kWh]||[kWh/a]||86.75||92.19||137.33|
|ID||Name||Details||Applies to||Changes Energy |
|Marginal Change in Price |
|BC 1||BC 2||BC 3||... Boiling|
by up to
|... Keep-Warm |
by up to
|BC 1||BC 2||BC 3|
|1||Indicator||Less overboiling through: Enlarged water level indicator, min volume, dual scale (in l and cup)||X||X||X||−10%||−10%||None||None||None|
|2||Heating||Thick film heating element||X||X||X||−8%||−8%||+3.50||+2.00||+2.00|
|3||Electronics||More accurate T-sensor, 95 °C target temperature||X||X||X||−5%||−5%||+4.00||+4.00||None|
|5||Temperature||Allows temperatures below 95 °C to be selected||X||−3.5%||None||+2.00|
|6||Keep-warm||Max 30 min||X||None||−50%||None|
|Scenario||BC||Design Options Implemented||Annual Energy Consumption [kWh/Year]||Purchase Cost [EUR]||Annual Maintenance Cost [EUR/Year]||Energy Consumption of the EU Stock in 2030 [TWh/Year]||Expenditure for the EU Stock in 2030 [Bn. EUR/Year]|
|LLCC||1||1, 2, 3||73.6||23.5||3.3||7.4|
|2||1, 2, 3, 5||70.0||34.0||4.0|
|3||All (1, 2, 3, 4, 6)||75.0||67.0||4.2|
|BAT||1||All (1, 2, 3, 4)||72.5||25.5||3.3||7.2|
|2||All (1, 2, 3, 4, 5)||68.9||37.0||4.0|
|3||All (1, 2, 3, 4, 6)||75.0||67.0||4.2|
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Durand, A.; Hirzel, S.; Rohde, C.; Gebele, M.; Lopes, C.; Olsson, E.; Barkhausen, R. Electric Kettles: An Assessment of Energy-Saving Potentials for Policy Making in the European Union. Sustainability 2022, 14, 12963. https://doi.org/10.3390/su142012963
Durand A, Hirzel S, Rohde C, Gebele M, Lopes C, Olsson E, Barkhausen R. Electric Kettles: An Assessment of Energy-Saving Potentials for Policy Making in the European Union. Sustainability. 2022; 14(20):12963. https://doi.org/10.3390/su142012963Chicago/Turabian Style
Durand, Antoine, Simon Hirzel, Clemens Rohde, Marcel Gebele, Carlos Lopes, Emma Olsson, and Robin Barkhausen. 2022. "Electric Kettles: An Assessment of Energy-Saving Potentials for Policy Making in the European Union" Sustainability 14, no. 20: 12963. https://doi.org/10.3390/su142012963