[jewel]

It would probably make more sense to store the heat of summer into the ground directly, using something like a ground source heat pump. An additional benefit is that the same system cools the house in the summer cheaply.

My friend has an off-grid cabin and his solar panels were easy to size for all other energy needs during winter by having them installed angled towards the winter sun position.

He does have a small generator just in case there is a particularly bad winter storm, but even in that circumstance it just has to run long enough to charge his batteries, so fuel consumption is minimal.