Question about watt hours

[TrashPanda10k]

I am curious about how one would use a water heater like this. Do you let it heat and then run more cold water in to flush/use the hot water?

It works like a regular water heater. Cold water in one pipe, hot out the other. I have it plumbed to take the place of the currently broken propane hot water heater. I was using the concept of cycles for everyone, myself included, something to use for calculation.

 

[Hedges]

Ideal would be if you could have electric and propane heat, because when battery is full excess PV could divert to water heater.
If you can deal with space and weight, might feed output of electric into propane.

 

[TKETON]

My solution to hot water... I have a 60 gallon 220ac hotwater heater. dual heater units. I replaced the upper heater with a 110 vac heater element and replaced the lower heater with a 36 vdc element. I connected the lower to two solar 300 w panels in parallel and i connected the upper heater to my 25,000 watt inverter/lifepo4 1,120 ah system. Here in AZ we have lots of sun, so its rare that i use the inverter. Been working perfectly for many years. seldom used inverter/battery, I maintain 110 F deg water temp.