I have an iHeat tankless heater. It will supply enough for a shower and sink simultaneously. There are different models.
220 volt line was already there as were in/out water lines....simple installation.
My first propane unit in another home had the electric bill go down $45 per month. Propane was refilled 35-40 gal every six months.
Propane units are even more efficient. Marey heaters out of Puerto Rico have been made for 60+ years now.
I saw no point in paying to keep 40 gallons hot all the time.
The only disadvantage of propane is the unit has to be vented to the outdoors.
“I saw no point in paying to keep 40 gallons hot all the time.”
I once measured the cost of a tank water heater that is only re-heating water (purposely did not use any hot water for a several days). It came out to being on for 12 minutes each day, in two 6 minute spurts. It was in an apartment, so the outside of it was room temperature, or really slightly below room temperature. So the daily cost, in those conditions, to keep the tank warm was around 15 cents, so under $5 a month. Still money, but it’s nice having hot water when the power goes out.
In a previous house (mobile home) it was straightforward to install a 220V tankless water heater as a replacement for a tank as well. And it worked great... 9 months of the year. Dec-Jan-Feb the heating delta was inadequate for a comfortable shower. Ended up installing a second tankless heater IN SERIES to get the water warmed up enough in winter.