Maybe my math is wrong.
Isn't 400 watts about 33 amp hours? that is if it is 400 watts at 12 volts vs 110.
Assuming a 15 amp draw, maxing out a normal circuit in a home, isn't that more than enough to power it? Assuming he has 180 amps worth of battery to power it during any lulls?
That would be a 1800 watt heater on a 120 v circuit.
Not sure what the losses are on an inverter though.
That also might drive up the costs quite a bit.

Also OP, don't forget about the noise. Apparently windmills can be quite loud. Vertical wind mills or a bunch of micro ones on the barn might also help.