Are rooftop photovoltaic systems a sustainable solution for Europe? A life cycle impact assessment and cost analysis

Global energy demand is constantly increasing and recent projections show that this trend is going to continue with an average increase of 1.2% up to 2040. Since the building sector has emerged as a large energy consumer, in an effort to combat this trend, governments worldwide introduced various policies. The utilization of solar energy conversion systems are at the forefront of attention as they are considered carbon dioxide neutral and can be used in order to cover both electricity and heating load demands. Thus, these systems need to be thoroughly investigated taking into consideration the variations in the solar potential and the differences that exist in the electricity mix throughout Europe both in terms of cost, as well as of emissions, in order to assess their sustainability. In the current work a complete life cycle impact assessment is conducted for typical 4 kWp photovoltaic systems throughout Europe, and their environmental impact, sustainability, energy return on energy invested and payback period are calculated. The results highlight that although residential photovoltaic systems are considered "clean" and have a relatively low environmental impact throughout their life cycle, depending on the installation location and local electricity mix this might not be the case in the coming years. The energy return on energy invested ranges from 1.64 to almost 5 depending on location, while their simple payback period is less than 11 years in most cases, and as low as 5, without any subsidy.