The objective of this paper was to compare primary energy consumption and energy efficiency during the operation phase of different types and combinations of water heating systems in single-family dwellings. Systems with an electric shower, liquefied petroleum gas heater, and solar heater with electric backup were analysed. The analysis was performed by means of computer simulation using EnergyPlus. Three Brazilian cities with different climates were assessed, i.e., Curitiba, Brasília and Belém. The systems were compared in terms of final energy and primary energy consumption. Results showed that systems with an electric shower, which have a lower water flow rate, led to lower primary energy consumption. The solar heating system combined with an electric shower was the option with the lowest energy consumption, and the solar heating system with a heating element in the storage tank was the option that consumed more energy. The systems were sized according to the requirements of the Brazilian energy efficiency labelling for residential buildings, and the efficiency level was compared to the results of primary energy consumption. The electric shower was found to be the third lowest energy consumer, but it was ranked the least energy efficient by Brazilian labelling, while systems with high energy consumption, such as gas heaters and solar heaters with a heating element in the storage tank, were ranked the most energy efficient. Therefore, a review of the requirements and methodology of the Brazilian energy efficiency labelling for residential buildings is recommended in order to encourage the use of truly efficient systems. Public policies that encourage solar heating systems should establish requirements regarding the configuration and sizing both the solar heating system and the backup system.
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