This applies any time you hire someone to come into your home, but solar combines the logistics of a home improvement project with the risks of electrical work. Credentials and references are especially important.

“You wouldn’t hire an electrician who had never done electrical work to come into your house and change things around,” says Kelly Larson, an electrical contractor in California with 20 years of experience doing solar installations.

This is harder to predict, but, ideally, you want a company that will stick around for the lifetime of your installation. Since solar cells don’t have moving pieces, they tend to need very little maintenance, Larson says. Still, in the event that anything does stop working during the warranty period, you don’t want to realize that your installer isn’t around to fix it.