According to a study by the National Renewable Energy Laboratory (NREL), solar quotes from national installers are about 10 percent higher, on average, compared to those provided by local installers. However, if you decide a national installer is the best choice for your home solar panel installation, here are some of the biggest companies to consider: SunPower, Sunrun, Tesla, Trinity Solar, ADT Solar (formerly Sunpro), and Momentum Solar.