Give it your address, draw out your roof or backward solar array (or place wind turbines) and it will calculate your output for your area, quantify that in dollars and figure out the cost minus incentives for the setup. Then combine the two to figure out how long it will take to pay itself off.

For my home, covering the garage in solar arrays will generate $500 in electricity a year, and after factoring in incentives will cost about $15,000. This mean it will have paid for itself in nearly 25 years.

However I don’t know if that factors in the added the value the PV array gives to the house (I doubt it does).