Not a citation, but when I last looked at it for a cabin, the plumbing costs, pumps, and extra stuff required in addition to the normal heater drove the cost so

Not a citation, but when I last looked at it for a cabin, the plumbing costs, pumps, and extra stuff required in addition to the normal heater drove the cost so high that it was just cheaper to add more PV panels, which have been coming down because they are made in great volume. Someplace without freezing weather, or someone who might just say “too cloudy too long, no warm shower today” might have a different calculus.