A super-green/permie friend posted in an online forum* seeking advice about the most eco-friendly water-heater option. (Her water-heater is electric and she says it will need to be replaced soon.)
My response, edited slightly for this blog post:
As you may know, I made the transition to totally water-heater-free a couple years back.
Even in winter, I can still bear to take a cold sponge-bath (or cold outdoor “Peace Corps shower” with a small dipper/pot) because I first make sure to get my body very heated up from doing yardwork, walking errands, etc.
BUT in the colder months I do sometimes heat up 1-2 liters of water a day in an electric kettle and store it in an old Stanley thermos. Stays very warm, even hot, for 24 hours, mildly warm for several hours longer. Perfect for a warm spongebath or a warm version of that beautiful al fresco “Peace Corps shower.” (One of my favorite things is a shower under the stars. Great option in an urban environment, especially if you don’t have a seamless privacy fence, tall dense hedge etc. Or just make yourself a little outdoor shower stall; those are popular. Of course you can just shower indoors but I love outdoors.)
If I were to end up with family members living with me longterm, I would probably accommodate them with a small water heater, for shower only. Say 10-20 gal.
My problem with a tankless heater is that it removes the feedback loop of limited quantity. People get accustomed to infinite availability of hot water– not a good thing for planet or wallet.
Huge bonus: I love having one less appliance that can leak, break down, etc. Such a load off one’s mind! My approach may sound extreme, but it’s hard to beat the peace of mind of just not having to think about this at all.
You could also just experiment by turning your water heater off for a day or two at a time, or only turn it on when you have guests. That’s what I did for a while. (IMPORTANT: In cold climates, where the temperature gets below freezing on a regular basis, just turning off your water heater might not be a good idea; your water might end up freezing, breaking pipes, etc. I would not try this in a cold climate without doing a lot more research. At the very least I would drain the water heater, not just let the water sit in it with the heater off.)
*The “online forum” mentioned above is the “Socially Conscious FIRE” group on Facebook. I highly recommend it. Once you join, you can find the water-heater discussion I’m referring to by doing a search for November 28, 2020; or “I’m likely going to have to replace my (electric) water heater.” Laura’s post elicited lots of good alternative suggestions, including heat-pump and gas-powered water heaters.
And, the “super-green/permie friend” who initiated this discussion is Laura Oldanie of the Rich & Resilient Living blog, one of my top go-to resources about finance, thrift, and abundant simple living. Laura’s blog is delightful and packed with high-quality information.