My 2300 ft^2 (210 m^2) house in NC uses 11000kWh per year. I needed less than half my roof (the southern half) to be covered in solar panels to generate almost all my electricity (I do have gas air and water heating, however).

I'd like to build my next house to PassivHous or similar standards. I think I can get the energy usage to 5000 kWH anually. With the whole roof sloping southward, I think I'd be able to generate more than what I need for the house, even accounting for electric transportation.