da.bees: I had not thought about the reducing valve. I was just outlining one of the issues with the tankless water heaters. They also are not the best if you have hard water. Even the salt left after a water softener will cause issues with them.
I will just stick with a standard old water heater. They are proven and simple. The energy saveed is not that much if you use much hot water. They save more if you are not using much hot water.
As for worrying about losing power. That has always been a worry with livestock in confinement feeding yards. I used to have a PTO generator but a few years ago put in a stand by propane powered generator. That is the only way to go. Many fewer headaches when you lose power.
Have a good day!!!