We put 7.8kw on our roof on a snowy mountain town in Canada in a tight valley. In 12 months it generated $950 worth of power at $0.13/kwh, and we now have no power bill for our house and all heating and cooling with a heat pump.
We tore out the old natural gas furnace and had the line disconnected, saving us about $2k/year for the heating.
Game changer.