I could not find reference to this in the Search, so here goes.
Our wood-fired water heater is about gone, I just brazed it [rusted out pin hole] and must get serious about a replacement system. Wood-fired ones like ours--about ten gal.--the AquaHeater no longer made or imported or whatever. I've been looking for several yr. Nor are there any other wood ones I can find.
Would rather not run a coil in a wood stove which I'd have to heat up in summer. Our current heater has a water jacket around the firebox and does not heat up the room. Propane I don't want to buy and at 8500 ft. MSL it can be challenging to keep a high-BTU burner going, which knocks out on-demand heaters.
Anyhow, while I ponder trying to make my own wood-fired system, which means great care as for safety issues...
We have an excess of PV electricity many days. Batteries charged up by late morning and kept topped rest of day, [Outback MX60s]. I am wondering whether it would help to use some of this extra electricity to heat or partially heat water, probably sticking to 120 v. elements via our inverter as with the MX60s using 12 v. looks like a chore as was recently written about extensively over at the Outback forum.
So, I don't know how to calculate what I can expect running, say, a 1500 w. element 120v. to heat water in a 30 gal. tank, just an example. I know there are formulas, there have to be, but I don't know them and haven't run across them on the web. I realize one must consider temperature rise and volume. I am thinking a super-insulated tank such as one of the Vaughns to minimize heat loss in the stored water.
Can anyone set me straight?