I agree it's not _hard_, but your original assertion was "All I need to make that work is variable rates". Now, you're talking about installing additional HVAC

I agree it's not _hard_, but your original assertion was "All I need to make that work is variable rates". Now, you're talking about installing additional HVAC equipment and spending $$$. In the summer, even if you cool your house down to 60F, it'll be back to 70F in a couple hours max. Electricity rates from renewable overproduction do not vary on the timescale of hours. It's not a solution without new equipment to "store" the hot or cold that you produce when electricity is cheap.