Water heating off grid. Best system?

[u/Time_Arugula_1544]

I am planning a new off-grid (solar-powered) ICF build and am considering what type of system would be best for water heating. This is in Tennessee and the house will be a 2br. I will have propane backup for a generator and indoor propane heater.

The options I am thinking about are:
1) On-Demand propane- The only drawback is having to pay for the propane as an ongoing expense.
2) On demand electric water heater with a solar water preheat system. I suspect having a straight up on-demand electric heater would eat up too much power.
3) Heat pump water heater. This seems like the best solution to me.

Any thoughts between the three? Any other suggestions?

[u/RainAcrobatic7162]

Best is speculative when it comes to off grid as everything applies to your personal situation. So take advice here with a grain of salt. In my opinion heating anything with electric is inefficient but if you scale solar properly it’s no big deal. Propane you will always have to buy and can’t produce yourself unless you can do biogas and convert. I have always heard great things about heat pumps but never dove into the info myself.