One of my buddies got in at the right time with a 10kW solar installation at the start. Took 7 years to pay off the build but now he makes about 10k/year off it until the end of his 20 year contract. So first 7 years everything he made went into paying it off followed by 13 years at +/- 10k per year into his pocket. So far as well he has not had any real expenses related to repair but knock on wood that may change but at this point it has paid for itself and he has been in black for a few years now.