To achieve the 1.5 °C goal of the Paris Agreement, it is estimated that 70–85% of electricity generation must come from renewable energy sources by 20501. This requires large-scale investments in green technologies such as solar panels2,3. Photovoltaic (PV) systems convert solar energy into green electricity using solar panels. In the United States, solar energy would need to account for more than 40% of total energy consumption to achieve this goal4. Hence, countries around the globe have implemented policies that encourage household adoption of PV systems, or hereafter simply solar panels, through financial incentives (e.g., in the United States5, Germany6, and the Netherlands7), yet such policies are costly. Here, we show that behavioral interventions, that is, interventions that do not rely on regulatory or financial incentives, are a cost-efficient alternative to promote green technologies.
Behavioral interventions have been used in various studies to promote environmentally friendly behavior8,9,10,11,12,13,14,15,16,17,18,19,20. Such interventions nudge behavioral responses in various ways, for example, by giving real-time feedback on energy consumption9,10,11,12,13, setting the green option as the default21,22,23,24 or labeling products as green14,25,26,27. Previously, behavioral interventions have been aimed at, for example, curtailing energy consumption9,10,11,12,13,13,28, or increasing subscriptions to green electricity tariffs21,22,29,30. However, research evaluating the effectiveness of behavioral interventions for large-scale investments is scarce. In this study, we thus test the effectiveness of behavioral interventions in the form of message framing in the context of large-scale investments, namely, solar panels for retail consumers. Solar panels generate green energy, which has a positive influence on various aspects of household energy consumption, such as powering heat pumps, appliances, and electric vehicles. The potential environmental impact of these investments is substantial2,31. Therefore, it is crucial to develop scalable and effective strategies to promote the adoption of solar panels among the general public.
Message framing refers to changes in the presentation of information, such as for products, and typically provides a scalable and cost-efficient approach to induce certain behavioral responses. As a result, message framing has been applied to various settings, such as advertising32,33,34, health communication35,36,37, or pro-environmental behavior32,34,38. In the context of pro-environmental behavior, previous research on the effect of message framing focuses on repeated or low-cost behavior32,38,39,40,41,42,43 but not large-scale investments. For repeated or low-cost behavior such as choosing electricity tariffs, the findings are inconclusive: On the one hand, research has found that interventions targeting oneself are more effective32,38,44. In contrast, other studies have found interventions targeting the environment to be effective14,39,40,41,45,46,47. However, decision processes for repeated or low-cost behaviors are likely to be different from large-scale investment decisions, such as solar panels, as the latter requires detailed planning, significant up-front costs, and substantial time commitment48,49,50. Hence, previous findings on the effectiveness of message framing may not generalize to large-scale investments, which motivates our evaluation in the field.
There are good reasons why message framing targeting oneself or the environment might be (in)effective for promoting large-scale investments such as solar panels (see Supplementary Materials 1 for a detailed discussion). For messages targeting oneself, a common assumption is that individuals’ decisions are driven by self-interest32,41,51. Hence, interventions highlighting economic gains, such as additional earnings or cost savings, might be more effective in motivating pro-environmental behavior. However, the large costs of solar panels mandate a thorough economic evaluation regardless of whether people are driven by self-interest such that this may not be a key determinant of the decision to adopt solar panels. In general, investment decisions may depend to a large extent on financial resources52,53 or, at least, their perceived financial risks for an individual such that economic considerations may outweigh environmental concerns and attitudes51,54. People may thus be more likely to act when the decision to adopt solar panels is framed as an economic gain for oneself.
In contrast, individuals are also driven by group interests51 and the desire to maintain a positive self-concept39,41. People often acknowledge the importance of environmental preservation and express a willingness to engage in environmentally friendly actions55,56. Therefore, pro-environmental concerns are a strong driver of human behavior9,20,28,40,41,45,46,47,50. By highlighting the environmental benefits of behaviors like preventing harm to the environment and addressing climate change, individuals may be motivated to contribute to the collective social good51 and align with their positive self-concept39,41. Consequently, emphasizing the environmental gains may be effective in promoting a serious commitment to adopt solar panels.
Overall, it is thus unclear whether message framing targeted at oneself or the environment is more effective in promoting the adoption of large-scale investments in the form of solar panels. In the following, we propose messages designed to promote a serious commitment of retail consumers to adopt solar panels by targeting themselves or the environment.
For message framing targeting oneself, we test two messages, which are motivated by people’s loss aversion57. Specifically, we highlight cost savings versus additional earnings for oneself when adopting solar panels. Framing the decision to adopt solar panels as cost savings (versus earnings) is motivated by the fact that customers may associate the term “to save” with avoiding losses (i.e., their energy bill is too high), which may cause stronger behavioral reactions compared to “to earn”58. In addition, framing messages as cost savings has effectively increased support for green energy in previous research but outside of large-scale investments44. We thus test whether the following two messages promote solar panels: (1) Self-Save: “Save on average € 813 per year” and (2) Self-Earn: “Earn on average € 813 per year.”
For message framing targeting the environment, we also test two messages, whereby we frame our message as either reducing emissions, which highlights the prevention of environmental harm or generating green electricity, which emphasizes positive environmental outcomes. Here, previous research showed that preventing a negative environmental outcome may be a stronger incentive to adopt environmentally friendly behavior but again outside of large-scale investments59. To this end, we study the following two interventions: (1) Environment–CO2: “Reduce CO2 emissions” and (2) Environment-Green: “Generate green electricity.”
Overall, we test four different messages that are intentionally designed separately for each frame (see Fig. 1). As such, our messages may vary depending on the specific context of each frame so that they effectively elicit behavioral responses when targeting oneself or the environment (see Supplementary Materials 1 for details).
We test the effectiveness of message framing to promote a serious commitment to adopting solar panels in a large-scale field experiment without opt-in bias or financial incentivization. Customers (N = 26,873) were randomized to different messages targeting either oneself or the environment.
A shortcoming of prior research in the context of green message framing for large-scale investments is the focus on self-reported variables such as willingness to pay, attitudes, or intentions (e.g., refs. 50,60,61) while neglecting actual behavioral outcomes in the field2,59. Even if people report that they are willing to live environmentally friendly, it does not mean that they will act accordingly51,62. This observation is known as the “intention-behavior gap” and poses a severe limitation when measuring intentions instead of actual behavior. The intention-behavior gap may be especially wide for large-scale investments such as solar panels63. Economic abilities, regulatory frameworks, or personal living conditions can make it unfeasible to purchase solar panels but do not preclude participants in survey experiments from reporting an intent to purchase solar panels. In this study, our variable of interest differs from purchase intentions as we measure whether customers make a serious commitment to adopting solar panels in the field (i.e., whether they initiate the planning process and allocate the necessary time and resources, after having passed the feasibility check).
Solar panels have a complex sales funnel due to being high-stakes investment decisions. In contrast to many other goods (e.g., fridges, coolers, fashion), solar panels require detailed planning and custom installation, which often takes several months or even years. Thus, the first step in the sales funnel is the successful completion of a feasibility check, which is followed by a tailored planning process for installation. In our paper, we thus analyze whether a customer has made a serious commitment to invest in solar panels, i.e., they have started the planning process (and have therefore passed the feasibility check as well as have allocated the necessary time and resources for the planning process). This is a crucial step in the sales funnel and is later the dependent variable in our field experiment. Different from using completed installations, measuring commitments is beneficial in our context. The reason is that high-stakes investment decisions with custom installation naturally come with potential idiosyncrasies (e.g., some components may not be available due to production or delivery bottlenecks or some geographic areas may also have a shortage of installation workers), and, by comparing commitments, such idiosyncrasies are avoided in our analysis.
In this work, we test the effectiveness of message framing for promoting a serious commitment to adopting solar panels in a large-scale randomized controlled trial in the field with N = 26,873 participants. Using a between-subjects design, customers visiting the website of a nationwide online retailer are randomly assigned to the four messages targeting oneself (i.e., Self-Save, and Self-Earn) or the environment (i.e., Environment–CO2, and Environment-Green). We then estimate the causal effect of message framing through different interventions on the propensity of a customer to make a serious commitment toward adopting solar panels. Across all messages, we observe a higher rate of customers committing to solar panels compared to the baseline. However, the framing in terms of financial savings for oneself was by far the most effective, resulting in a 40% higher level of commitment than the baseline and 30% higher than the average of the other three messages, which were not significantly different in effect from each other. In our experiment, there is neither opt-in bias nor financial incentivization. Overall, our results show that message framing is cost-efficient and scalable among retail consumers to promote large-scale investments in green technologies and thus clean energy.
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