zlacker

>>PaulHo+(OP)
I wonder if this can store any heat or just heat pump heat. If it can store any heat, it would help a lot to further reduce heating costs in our modern energy efficient house.

Sometimes, in the winter, we get too much solar forcing, so if we don’t heat all, it can be 85F in the day in the house, but 60-65 at night. (We open the windows during the day, and don’t always close them at exactly the right time at night.)

>>hedora+QM
I think this can work and instead of that the heatpump pumps the heat into your house (when "solar is plenty") it would pump it into the storage. (I have a similar setup, but heat the water but of course this is rather limited)

unrelated: a simple technical solution to your window problem would be home assistant and a few sensors to notify you when the windows are open too long or open when too cold inside.