I don’t have any numbers for you but I would think using the hot water would cost more. You’re using X amount from the water heater, which gets replaced by cold water, which then reduces the temp of the water in the heater, so the heater kicks in to heat all 20 gallons plus the cost of the water you let go down the drain. Ping me if someone gives you numbers though, please. :)
Thanks for the attempt. I had not considered the reheating issue nor do I know the temperature at which the water is kept. Whether the amount of water I run each time would actually kick it on I don’t know.
I will try to find a more appropriate thread and get back to you when I get an answer I consider reliable.