This type of mini hot water heater can provide instant hot water for a sink and save both water and electricity.
Washing your hands these days is important, in terms of preventing the spread of the Norovirus and other diseases. But for many folks, getting hot water in their bathroom sink is a problem - you have to run the hot water for several minutes before the hot water tank feeds hot water to your bathroom.
In our house, built on a slab, the pipes run through the floor, which means that the water is COLD and stays that way for about five minutes after you turn the hot water tap on. Running the faucet like this wastes water and also wastes electricity as it has to heat all that water in the pipe, just so you can wash your hands or shave.
A small hot water heater, like this four-gallon unit above, can solve this problem. We bought ours on sale from compact appliance.com (they no longer carry them) for about $100 or so. It plumbs into the hot water line and hangs on the wall. Once mounted, in a cabinet under the sink, it is an easy matter to connect from the hot water supply (via a flexible hot water hose) to the water supply spigot and then to the faucet (using another flexible hose, rated for hot water).
The only difficulty was in finding 110V in a bathroom cabinet. However there was an outlet on the wall, on the other side, and it was a pretty simple matter to drill through and add a new outlet, with ground fault interrupter.
Do they work? Boy howdy do they! Hot water almost from the instant you turn it on - and as hot as you want. No more running faucets for minutes at a time, just to get enough hot water to shave with. And no more wasting electricity heating hot water than you never get.
If you have a bathroom or sink you use a lot and it is located a long way from your main hot water heater, these type of small, auxilliary heaters are handy, inexpensive, and also save energy and water.