The Effect of Variable Electricity Tariffs in the Household on Usage of Household Appliances

Abstract

Demand side management (DSM) has been discussed and investigated widely as a strategy to also influence residential energy consumption. Flexible energy tariffs are often proposed as a possible tool of DSM. However, real-life experience with this tool is rare. It was therefore the objective of this study to investigate under more realistic conditions how consumers are able and willing to adjust their residential energy consumption under the conditions of flexible energy tariffs with and without the support of intelligent smart appliances. Sixty-seven households in Germany within an experimental design with fictive tariff model (August 11 to July 12) driven by RWE Effizienz GmbH, as the energy utility, and Miele & Cie.KG, as the appliance manufacturer, were equipped with intelligent smart meters and 41 of them also with smart appliances (washing-machine and tumble-dryer). As a first part of the experiment, the energy tariff changed per hour and day by day, depending on the forecast of the availability of renewable energy in Germany between 10 €-Cent and 40 €-Cent per kWh. Consumers could respond to this change by adjusting the operation of their energyconsuming appliances either by themselves or—with the smart appliances—by a programmed start at low tariffs. The behaviour of the 41 consumers with smart appliances and their motivation are intensively investigated and analysed during this running two year project including several questionnaires. The consumers had to fill out daily a diary about the usage of their washing-machine, tumble-dryer, dishwasher and ironing devices. These data were matched with the actual tariff. This did allow identifying if and to which extend the consumers adjust their household activities depending on availability of solar and wind energy. These data were also used to calculate the cost savings by using the flexible tariff. In comparison to the costs of the fixed tariff of 25 €-Cent per kWh savings of 25% were realised on average. The results of a first phase already show that flexible tariffs are able to influence the operation of household appliances towards a flexible demand.