Unless the dishwasher is you & Lena, your appliance may already have a heater installed in it to get the water up to temp.
But of course that uses electricity instead of gas and might drive up the cost a tad.
Yes, it has that but we don't use it in order to save money. Also, it takes a lot longer to run when it heats the water, and it keeps making noise the entire time.
Can you plug the controller into an old UPS? I'm assuming it is a gas heater.
A UPS might not provide enough electrical power for a shower.
Yes, exactly correct, and we've done that when the power is out. It only draws 4 watts of electricity. I already have the TIVO and the modem and router on UPSs, and that's helpful for those 4 second outages. Next time I see one at a garage sale I'll get it for the water heater.
Would bringing up the maximum to 135 bring up reset to 123?
I don't think so, I read that it's a safety thing.
108 degrees should feel plenty warm for a shower.
Yes, but it's lower at the shower head, possibly because it's low flow. But that gives me an idea. Next time, maybe I'll just turn on a faucet instead of running around.
If you have a one-handle temperature control on your shower, there is a stop that is usually adjusted to prevent you from getting 100% hot water.
Yes, I've already adjusted that to maximum.
-------------
We have to train ourselves to not think "Yay, the power's back on" but instead "Yay, the power's on, let's reset the water heater."