What makes people decide to put solar panels on their roof? Surveys show it’s not their age, their race, their level of income, or their political affiliation. The determining factor is whether their neighbors did it first. Now Google is putting this finding into practice. Next week the company’s “Project Sunroof” is adding a new feature and will show you which of your friends have already put solar panels on their roof. Project Sunroof will now not only inform users how much sun hits their roof, or how much solar panels would save them per month, but also which of their neighbors have taken the plunge first.