> I don't think there are even any widely available on the market today which will automatically increase the temperature at mid day in anticipation of an elect

> I don't think there are even any widely available on the market today which will automatically increase the temperature at mid day in anticipation of an electricity shortage later. Our house built 7 years ago has an Enefarm fuel cell/hot water heater. Every house in our neighborhood and every house I’ve seen by the same builder has one. It approaches things a little bit differently but to the same effect. It learns your energy use patterns and turns on the fuel cell (using LP gas) when you usually use electricity, generating hot water as a side effect. The future is already here, it’s just not evenly distributed yet. https://www.j-lpgas.gr.jp/en/appliances/index.html#ENE-FARM https://www.j-lpgas.gr.jp/en/appliances/index.html#ENE-FARM > it's a safety hazard in homes with small children; hot water temperature should never be hot enough to cause burns when someone turns on the faucet. Internally it stores water at 65 degrees C but mixes it with cold water to to supply all water to the house at a certain temp. We have ours set to 40C but you can change it on a control panel. Of course, there are mixing taps at the sinks/showers. It’s very common for shower temp controls here to have a extra stop at 40C that requires pressing a button to exceed. > Most homes don't have enough free space for a big pile of rocks to increase thermal mass I don’t know about cooling but the ones that take advantage of cheap electricity at night to store up heat and release slowly over the day are not massive. https://catforehead.com/2014/02/17/getting-warm/ https://catforehead.com/2014/02/17/getting-warm/ https://www.sanica.co.jp/aldy/products/rdf40.html https://www.sanica.co.jp/aldy/products/rdf40.html