He's got a tankless hot-water system fired by an oil furnace, and in the summertime he only turns on the furnace to take a shower, using the red wall switch to turn it on and off. For the rest of the day, the furnace is off and the house has no hot water.

We've got the same kind of system (tankless oil-heated), so we're giving it a try.

Our dishwasher and clothes washer both have internal water heating devices, so they only use a cold water supply anyway.

I wonder if it'll actually save us any money...