Depends where you are. In Australia it's pretty cheap - I had 6.6kW installed for about US$4000 and it should pay off in about seven years. Would have been five

Depends where you are. In Australia it's pretty cheap - I had 6.6kW installed for about US$4000 and it should pay off in about seven years. Would have been five or six but the feed in tariff went down - although with the massive increase in the price of coal and gas, the tariff should increase again, given the wholesale electricity cost is jumping up.