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> timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection)

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.

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My heat pump water heater is at 140F all the time, maximizing the banked energy. There's an outboard mixing valve to reduce this to a safe temperature in the house.

https://patents.justia.com/patent/20180290899 provides background on the topic. Keeping your hot water tank at or above 50-55C constantly is a reasonable mitigation, anything hotter can cause scalding.

You can't scald yourself with mixed water from the faucet unless you set the faucet lever wrong, so I've never had that issue. In addition to that, the recommended high temperature setting (I believe the recommended default setting on my tank is 60 C?) increases the amount of mixed water that you can use before depleting the tank, so even a smaller tank suffices for a person.

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