The combination of a big federal tax credit, incentives from many utilities and states, better and cheaper panels, and millions of consumers wanting to reduce their use of fossil fuels has begun to generate an era of widespread residential solar energy use. If you’re thinking about going solar, there are many decisions to make, each of which will impact how much you’ll spend now, how much you’ll save over the life of the system, and whether you’re eligible for tax breaks and other incentives.

Because standard residential solar energy systems seldom cover all electricity costs, you probably won’t say goodbye to your power company—or its bills. But you will save big bucks each month. Despite these savings, the biggest obstacle for most homeowners remains cost: To buy a standard-size system, you’ll have to plunk down about $20,000. A 30 percent federal tax credit will pay for a chunk of that, and over time your lower utility bills will add up to pay for the rest—eventually.

Begin by making sure your home is a good site for solar. Then check the condition of your roof. Because solar panels last for 25 years or more, and because your roofing shingles will need equal longevity, ask a good roofer if you should replace shingles where you plan to install panels.

Be sure to thoroughly vet solar contractors you consider. When our mystery shoppers asked companies to propose systems, they received wildly different proposals, some of which included overly optimistic or haphazardly calculated estimates of payback periods. We discovered some fairly big price differences, too.

Before hiring an installer, nail down all details in a contract. Read everything, and ask the company to clarify anything you don’t understand before you sign.