Google's Project Sunroof, which examines the viability of solar installations on homes in the US, has found 4 out of 5 homes have solar power potential. The project began two years ago and has surveyed 60 million buildings across 50 states.
Although there is state-by-state variation in solar viability, 79% of US homes could potentially benefit from a solar installation. That increases to 90% in areas like Hawaii, Arizona, and New Mexico. Meanwhile it's closer to 60% in Maine and Minnesota.
You can use Project Sunroof to figure out how much sunlight your roof receives and therefore the financial aspects of using solar power. Google figures out your sun exposure based on a "3D modeling of your roof and nearby trees," weather patterns, and the position of the sun during the year.