The general solar payback period is about 5-10 years. Cost factors include the size of your solar system, how much solar panels cost per watt in your city, and which financing options you choose. With cash purchase solar you can pay off your solar panels in as little as 6-18 months. With solar financing you can pay off your solar panels in about 5-7 years. With the average lifetime of solar systems being around 25 years, this means the system will pay for itself and will save you a ton of money.