When households acquire a PV system, they become prosumers: they not only consume energy, but also produce electricity themselves. This can lead to behavioural changes that influence the overall consumption of the household. The EE-Rebound project has investigated such rebound effects. This working paper analyses the ecologic and economic impact of the behavioural changes at the household level.
A simulation model was used to represent prosumer households. Generation, self-consumption and feed-in of prosumers are simulated in different scenarios. The scenarios are characterized by different consumption patterns, household sizes, and system sizes. Overall, as expected, the switch to prosuming results in lower grid purchases compared to pure consumption. Furthermore, it becomes clear that total consumption as well as grid purchases increase due to rebound effects as well as additional consumers, while grid purchases can be reduced by load shifting. Even though feared curtailment can be a reason for additional consumption after the installation of a PV system, the simulations were able to show that curtailment is actually unproblematic, as it is relatively low in all scenarios.

In the ecological assessment, in addition to the scenarios, differences regarding the electricity purchased from the grid are also investigated (grey electricity vs. green electricity). The ecological impact is mainly dependent on the electricity provider of this additional grid purchase or its emission factor. Due to additional consumption and additional consumers, emissions also increase with grey electricity purchases. A larger dimensioning of PV systems and batteries reduces the grid purchase and thus also the ecological impact of possible rebound effects. However, the additional self-generated and consumed PV electricity is not fed into the grid and is accordingly missing from the grid.

The economic evaluation shows the effects of the behavioral change when switching to prosuming, as well as income changes for the prosumer household in the different scenarios. The switch to prosuming leads to positive income changes for the household when the systems are comparatively small in size. This positive development can be enhanced by sufficiency and load shifting or reduced by rebound effects. Larger dimensioning of the plants leads to negative income changes above a certain value. In addition, the type of financing (amount of interest and proportion of equity and debt) also has an influence on the economic effects for the household.