[Ndymium]

This is essentially what a ground source heat pump system is. Except instead of a sealed water tank you just make a tall hole that fills with water and the sun will warm it for you during the summer automatically.

1800 kWh is very little. We use around 12000 kWh and our neighbours' new house uses around 8000 kWh annually and most of that is heating. I'm not sure how many houses can hit 1800.

[nandomrumber]

A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons.

https://en.wikipedia.org/wiki/Ground_source_heat_pump

[Maakuth]

You can also recharge your geothermal well or ground heat collection field by heating the outgoing thermal collection liquid with either cheap electricity (rooftop solar?) or direct solar heat collection. I think this will be a growing thing as the earliest mainstream ground source heat wells start to be a few decades old. Many of them are sized so that they don't fully recover during the summer, so the heat output slowly drops.

[Maxion]

Heath energy required != electricity requirement.

A modern house in Finland needs around 15-24kWh a year of heat energy if it's well insulated. On the higher end for big + northern houses, and less if you're smaller and further south.

Some get this energy by burning wood, others with heat pumps, and some with direct electricity.

[nandomrumber]

24kWh is 1kW drawn continuously for 24hrs.

That can’t possibly heat any home for an entire year.