A comparative survey of investment conditions for solar facades and rooftop PV in building applications

• We study the investor perspective concerning solar facades. • 26 interviews comparing integrated and mounted solar facades to rooftop PV. • Integrated facades cost 3-5x more, with 15-year longer payback than rooftop PV. • Building decarbonization also driven by non-economic investment dynamic. • Sustainability criteria and making a visual statement main investment drivers. Photovoltaics (PV) are a key technology for low-carbon power generation, especially in cities where rooftop systems are widely adopted. Despite the larger surface area and solar irradiation potential, building facades remain vastly underutilized compared to rooftops. Yet using them for solar electricity could substantially boost cities’ decarbonization efforts. Here, we analyze why solar facades lag behind rooftop PV, focusing on the financial and investment perspective in Switzerland, a country with among Europe’s largest solar facade deployment rates. Through interviews with 26 solar planners and architects, we analyze investment conditions – investment costs, operational costs, capacity factors, payback periods, and development timelines – for two facade types (facade-integrated and facade-mounted) and compare them to rooftop PV. Our findings reveal that compared to rooftop PV, solar facades feature three to five times higher investment costs, four times longer development, and 30 % less electricity per kWh output due to the vertical orientation and shading. These conditions result in mean 25 to 27-year payback periods for integrated facades versus 14 to 19 years for facade-mounted ones, depending on the size. We argue that future policies must simultaneously foster economic and aesthetic incentives to boost the adoption of solar facades, advancing sustainable urban decarbonization.