heatpumps are just amazing. Newer inverter type claims to work down to 5F, such as this one from Amazon:Mini-Split heat pumps and heat pump hot water heaters are very efficient (3-4 times than electric element heating) if a temperature outside is above 35F. I have 1 in each room, and they also work as AC during the summer.
This can greatly reduce the size of solar panels and batteries.
am waiting for 2023 to install a few, with tax credit incentive.
Our central whole house heatpump was cranking out ~80F inside while it was 20F outside last winter. We also discover direct radiant heat, like those "heat dish".