Load shifting of domestic water heaters under double price tariffs: Bringing together money savings and comfort

Demand Side Management (DSM) programs can offer residential electricity consumers opportunities to cut their energy bills. However, if such programs significantly downgrade comfort of consumers, they can choose to opt them out. This impedes the DSM implementation in practice and declines the efficiency of DSM in overall. Finding ways how consumers can reduce their money expenses with least impact to their comfort is thus desirable. This paper focuses on tank electric water heaters (WHs) under double-price tariffs as a case of energy storage devices under simplified variable pricing. We investigate whether or not the WH load shifting can bring money savings while maintaining the user comfort based on the introduced expenses-comfort balancing approach. The proposed approach is based on day-night energy rates and the energy-comfort model suggested earlier. The refined energy model constitutes the first contribution of this paper. As the second contribution, we reformulate the energy-comfort balancing problem into the problem of `expenses-comfort balancing'. By simulating diverse hot water usage we show that the proposed mechanism can enable monetary savings without significant drop of comfort. Specifically, the customers can reach up to 20% of daily money savings compared to the regular operation of the heater during weekdays. The reported research can be of interest to utilities that focus on improving consumer uptake of DSM.