# A Heuristic Approach to the Decision-Making Process of Energy Prosumers in a Circular Economy
## 3 Case Study and Method
### Avoiding electricity network dependency;  
#### Reducing environmental impact using renewables. For closed questions, answers were structured according to the following Likert scale: 1 \"not relevant\", 2 \"rarely relevant\", 3 \"relevant\", 4 \"very relevant\", and 5 \"totally relevant\". Considering pre-installation (Part C of the questionnaire), respondents considered the five factors as \"relevant\" (3) at the very least, although some differences were noticeable, as shown in Figure 1, which includes the average values (all above 4 \"very relevant\") and dispersion. Using box plots, we could identify the median of all the answer values and graphically illustrate the interval in which the most common and, therefore, most representative values fell. The mean is also included in these figures. Vertical lines show the rank of the obtained answers, and colored boxes allow seeing the dispersion of answers. Colored bars show the 25 th and 75 th percentiles as a function of the median, i.e., each bar covers the central 50% of data. A larger colored box denotes greater dispersion of the answers. An inexistent colored box means that the values were barely dispersed, although the median could have differed from the average value due to atypical values. Responses to an open-ended question related to the motivations when installing PV systems revealed that responders considered energy security and energy independence as part of the economic benefits, as they felt that they were \"less vulnerable to changes in the electricity tariff\". On the other hand, \"influence of others in the neighborhood with PV systems\" and \"influence of a close acquaintance not from the neighborhood\" were not considered relevant factors in the decision to install PV systems. This is mainly because the spatial distribution of these systems was sparse; the respondents were largely \"innovative\" adopters. Finally, at the end of the interview (Part D in the questionnaire), respondents were asked to rate the performance, operation, maintenance, and financial attractiveness of their systems post installation. The same set of questions as in Part C1 (see Figure 1) was used in order to compare the obtained results. This approach was expected to eliminate the subjectivity seen in pre-installation answers from the average values and data dispersion. By comparing the average answers shown in Figures 1 and 2, the following conclusions can be drawn:  
* Regarding the level of general interest in energy self-generation (C1.1 vs. D1) or environmental concern (C1.5 vs. D5), we can say that internal attitudinal factors were unchanged on average, but dispersion increased in the answers related to the second issue. Figure 1: Relevance level (average and range) of global factors in the pre-installation phase. * Economic concern was displaced from savings (C1.3 and D3) to home value (C1.2 and D2). After installation, prosumers identified the possibility of improving the value of their home. However, owners did not perceive a reduction in their total electricity consumption post installation of PV systems, and the independence of the grid was not as high as expected. * Regarding avoiding electricity network dependency (C1.4 vs. D4), the reduction seen in the range of answers could have been due to the fact that any perceptions were now evidenced. Economic and financial aspects are expected determinants in the adoption of PV self-consumption; thus, Part C.2 was intended to gather the interviewee's thoughts with regard to the relevance of price (C2.1), access to financing (C2.2), payback (C2.3), operation and maintenance costs (C2.4), and regulations (C2.5) in their final decision. Answers are shown in Figure 3.  
Prosumers were asked to select the tool used to establish the economic viability of their installation (internal rate of return, net present value, etc. ), revealing that a cost-benefit analysis was implemented by all respondents.