If you had a modern well insulated house you could heat your house with a hair drier in the dead of winter in climate zone 5. If your stacking up to 4mwh then your house is not really a good example.
I mean... that's all our energy inputs, including pumping water from a fairly deep well, almost all our transportation miles (300-400kWh/mo), heat, hot water, etc. It's a ~7 year old manufactured, 2k sq ft, 2x6 exterior walls, pretty tight (blower door and ducting tests have concluded "Nothing to fix here"), though I'm still running down a few weatherstripping issues on one of our doors.
A 1800W hair dryer running constantly is 1.3MWh/mo, and this isn't 4MWh/mo, it's since about Nov, on a colder than usual winter. I'm right on the north end of Zone 5.
In any case, I've yet to figure out how to get our heat pump outdoor unit from freezing up in icing fog, but neither is it worth $20k to put a ground source unit in right now.
