seasonal solar hot water
There are a couple simple ways, a coiled hose in the sun is a good one. I have been back to using my camping Solar shower ( a non-sustainable plastic bag with hose) it is ripping at the handle area, it likely was never made for day to day use.... Before they break, if you see on at a garage sale, you can hang up next to the kitchen sink to do dishes, or hang off of the shower head arm in the shower. So, it is portable and cheap or free to get hot water. SInce mine is ripping, and for the moment, due to COVID, no-one is dropping by my yard, so I just leaned it againt the top deck step and did a "camp" wash off/shower below it on the steps. It was actually realy nice to do such business outside in the sun ! The water was almost too hot. Last night, I hung it next to the kitchen sink to do dishes with hot water, will get a photo tonight ( yesterday I dropped this phone into a bucket of water, so had no way to take photos).
I am practicing my extreme resource useages again right now, one for the practice. And 2, because I am one of the people who has suffered an extreme income drop due to COVID lockdowns. SO, I cancelled trash service, water heater may stay turned off, and I may just turn off the pressure pump, and I am being more vigilant on the well pump time of use. Need to go clean the filter so it doesnt work so hard too. Powering down a little is good practice. Large garden is in.
I would think that there should be a sustainable way to heat water outside and bring in -- maybe a plywood box with glass on top with a covered bucket of water inside, like a ashcan, they have handles and lids, an example, but buy it local https://www.amazon.com/dp/B00QFHEVAC?tag=duckduckgo-ffab-20&linkCode=osi.... Then it could be carried in and used in the bathroom or kitchen sink.
Here is an example of a basic seasonal solar shower outdoors in a yard, this guys have lots of low impact ideas https://www.low-carbonlife.org/post/solar-shower-blues
And that is why I have the idea that a smaller version, where you take the top off, with the ash bucket inside, would allow summer hot water to be brought inside