If you have a consistent schedule, you can also use timers for those so you don’t always need to remember to run it.

Most houses in the US have a single water heater, usually in the basement or utility room, with pipes running all through the house.

I thought a hot water circulator would be great, and it kind of is, but it comes with a drawback that I hadn’t considered. If you want cold water from the tap, to fill a glass of water at night for example, you have to wait for that just as long as you would have had to for the hot water before!