A less-sophisticated approach is to put your tank heater on a timer. Think carefully before you do this. Does your tank heater have the capacity to keep the water hot for a full shower, until you’re back under the non-peak schedule? If it doesn’t, you’ll be the first to hear about it.
Do not do this without understanding the lifecycle of legionella pneumophila, or you will face a dramatic decrease in your quality of life.
Greek public health announcement regarding outbreaks ~2018: https://www.acg.edu/about-acg/institute-of-public-health/fac...
An anecdotal account of a man contracting Legionnaire's while on holiday in Greek apartment: https://www.irwinmitchell.com/news-and-insights/newsandmedia...
An older account of a similar ocurrance in a hotel, just as you describe: https://www.sciencedirect.com/science/article/abs/pii/004313...
Granted, no mention of this particular cultural artifact. Global temperature warming was cited in some reports as part of the cause of these outbreaks. It seems that the bacteria really likes to live in showerheads, so especially older shower heads can accumulate legionella especially given commonly lukewarm temperatures. This creates a perfect storm of ideal reservoirs, protected, moist, temperature conditions and aerosolized distribution.
Nasty.
Tankless heaters are great if you’re burning gas, but electric versions are wildly inefficient versus a heat pump and require very large circuits and service entrances on the load center/breaker panel.
This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.
Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)
None of this applies if the water heater is not in a conditioned space, but that's not feasible in (common) environments with cold winters.
The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.
I urge great caution, although I'd wager you'd be fine, so long as you remain healthy.
If you do the "bare minimum 140f once a day" method, you have to flush all the hot lines with this for long enough to kill it.
All this also presumes correct thermostatic calibration and generally even temperature distribution in a system planned to age with minimal maintenance.
The process isn't instant, you also have to ensure the hot water hits all the lines down the way at the appropriate hold temp and, well, hold it there for long enough.
These outbreaks still occur today. Not a huge problem, but why design such a well controlled hazard back into your potable water?
Where I am, you’re not allowed to deliver water to fixtures higher than 49C (120F), to reduce scalding risk. and this is usually accomplished through a mixing valve at the hot water tank outlet.
11m people live here, haven’t heard of any evidence of increased legionnaires:
All that other stuff assumes a minmax hot cycle in a waterheater tank.
On demand heaters work fine too.
When I replaced my water heater, I went with the hybrid model and dropped the AC. The room stays cool, my water heater uses less power on average and I don't have to fire up the ac unit at all.
Alternatively a tankless water heater provides both redundancy and instantly hot water.
I’ve been intending to do solar water heating, and convert from gas to electric, but the old heater gave out at the wrong time. So the current plan is build the solar and make a new place to move the electric tank into, then use the other tank for extra storage of the solar heated water. The good news about climate change is that I never have to worry about the pipes freezing any more.
As they recently learned in Texas.
The only saving grace at the coasts is that you’re sitting beside a giant heatsink.
So maybe plan accordingly just in case....