Founded in 2011, Vivint Solar is a renewable energy company that sells, installs, and maintains PV solar energy systems. The company is one of the most talked-about solar panel installers in the industry, in part due to its notorious door-to-door sales approach. Vivint Solar was one of the first rooftop solar companies to offer a power purchase agreement (PPA), which allows customers to pay only for the power the system produces during the life of the contract — often at a lower rate than their electric bill.