Hot water is provided by a 20 gallon, Seward marine hot water heater located directly overhead of its point of use. The tank is the gray box between the Sun Tunnel skylights. The white lines are PEX plumbing.
The main reason for choosing a tanked over a tankless, on-demand heater was that it has a heat exchanger built in. On a boat this would be connected to the engines cooling system. In my case I plan to connect it to my wood cookstove. I bought the accessory heat exchanger for the stove, but I have no idea where it gets installed. A future project. Locating the tank in the attic means that convection can be used to circulate the fluid instead of a pump.
I have experience with both electric and gas on-demand hot water heaters and I'm not sure why anyone uses a conventional water heater anymore.
The heater is on a timer that shuts it off overnight. The heater is small, well insulated and mounted in the attic in conditioned space. Unlike many water heaters that are located in garages, trying to keep water scalding hot on winter nights.
The heater also runs on 110-volts, holding out the idea that it could run off the solar side of the electric system.
Ideally Auerhaus would have solar hot water in the summer, wood in winter and electric only as backup. Although I'm told solar hot water has a payback of only 3-years, I found it really hard to get enough solid information to put it into the original design.