> you can get a 5kw battery for 2k. Good luck running water plumbing and radiators throughout your house for 20k
That's not quite apples-to-apples; the energy from the battery also needs distribution through the house. Of course, every house has wiring, not all already have radiators.
But on a price basis, you can get a 5kw battery for 2k. Good luck running water plumbing and radiators throughout your house for 20k