I’m reminded of the electric water heater at a house we once lived in. It had a 40 gallon tank, rated to use about 4700 kWh annually.
Since we needed optimally hot water only when we showered, we installed a mechanical timer to heat the water for just 3 hours a day, instead of 24.
At that house, our front loading washer would heat the water it needed. Lukewarm water for other needs, such as hand washing and dish washing was acceptable to all members of the household.
We liked that operating the water heater for 3 instead of 24 hours would shave the electricity usage by 87%.
Over a couple of years, we found that we occasionally lost power, and there was the twice a year clock adjustment for daylight savings time. This meant the hot water wasn’t ready when we were ready to shower! Also, I grumbled about going to the cold basement to change settings when we needed to shower outside of our usual routine.
So we replaced that mechanical timer with a digital timer. This time, the timer adjusted for daylight savings time on its own. And, we installed the control at the top of the basement stairs, just off the kitchen. This meant I could alter settings while getting my morning tea ready, in my pajamas. Pushing a button for a quick override meant a good shower within 10 minutes at any time of day or night.
We still kept the water heater running for the 3 hour window we allowed ourselves to get ready each morning. This meant we still got that 87% reduction in electricity usage, from 4700 kWh to 580 kWh.