An excellent article describing the interdisciplinary approach of rebound effects in German solar photovoltaic user households (prosumer) has been recently published (Galvin et al. 2022). Authors highlight the most important steps of their interdisciplinary process: an engagement to dialogue between various background researchers, to design “from the beginning” an interdisciplinary method and findings analysis strategies, to identify the detailed role of each researcher teams, and to develop a shared vocabulary.

This paper presents an overview of method, findings, and common analysis/interpretation of 3 studies (see Fig 1). This research team explored the potential rebound effect in term of electricity consumption in prosumers.

Qualitative interviews of rural prosumers (N= 19)

Three frameworks emerged form thematic analyses: a “geo-sociotechnical” domain (association between technology, self-regulation and sun), interaction between ‘positive and negative’ rebound effects, and financial/psychological explanations. An “income effect” also was identified in early photovoltaic adopters (i.e., 2000’s). Indeed, extra electricity was purchased around 0.5 euro/kWh, and household ‘benefits’ may have been associated with more travels,.. Here, it was not necessary a rebound effect in term of electricity consumption. A ‘price effect’ was observed (i.e., the kWh price was lower in more recent adopters), so it was less interesting to purchase its own electricity. A moral licensing effect was reported among participants.

National online cross-sectional questionnaire (N= 1291 vs 297 (non)prosumer).

Prosumers were younger, lived in a larger house, had higher incomes, had more frequently a heat pump, and high level of environmental concerns. Researchers would quantify a possible rebound effect occurring after households install a photovoltaic system. To identify possible correlated of rebound effects, they also collected data about attitudes, economic incentives, and behaviors. No significant differences was observed for electric consumption between (non)prosumers (even if I don’t clearly understand their statistical approach).

Data analysis of co2online dataset

This no profit organization have a data-set of people self-reporting their electricity consumption (1992-2018). 79 households reported their consumption before and after their photovoltaic system installation. A rebound effect of 9.6% was found. Authors highlighted a possible limit, a possible self-monitoring effect on electricity consumption. In other words, this rebound effect may be underestimated.

As expected in an interdisciplinary research project, all findings were collectively discussed. The team decided to ‘re-run’ their analyses to investigate the effect of feed-in tariff (major change in 2011 from 0.5 euro/kWh to 0.09 euro/kWh, see Fig 3) and regulations changes (i.e., allowed self-consumption) on their previous results.

A significant difference was found between (non)prosumers in 2011 sub-sample, prosumers consumed more electricity (18%, c-à-d 675.57kWh/y) than control participants. A rebound effect of 14% was observed. Analyses based on co2online data-set suggested a possible rebound effect of 33% in post-2011 installers. It is important to note that ‘income effect’ was reported in interview only in pre-2011 users. Again, the level of self-reported environment concerns (questionnaire measure) was not related to electricity consumption. It contrasts with findings from some interviews. Furthermore, authors suggested that this important rebound effect in post-2011 prosumers could be problematic because it decrease the renewable electricity going into the grid.

By extrapolating the findings and conclusions, this investigation may be a good illustration of interdependence between decision to buy a solar photovoltaic mostly based on (economic and ‘rational’ psychological factors), the system rules moving (e.g., kWh price), technical and power improvements of photovoltaic systems, and strengthened personal ecological values (for better of for worst). This figure synthesizes this idea.

• Galvin, Ray, Johannes Schuler, Ayse Tugba Atasoy, Hendrik Schmitz, Matthias Pfaff, and Jan Kegel. 2022. “A Health Research Interdisciplinary Approach for Energy Studies: Confirming Substantial Rebound Effects Among Solar Photovoltaic Households in Germany.” Energy Research & Social Science 86 (April): 102429. https://doi.org/10.1016/j.erss.2021.102429.

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