You are exactly right. Assuming you have an electric hot water heater, it cost about 8 cents to heat 5 gallons of water (assuming 65F to 120F temperature rise). The recirculation pumps will result in water being heated repeatedly during the day. If you go that route you might want to consider putting it on a timer so it only recirculates during those times that you are likely to use the shower.
BTW, 5 gallons of water costs about 3.5 cents. I am not sure how the OP is using 5 gallons of water before hot water shows up. With the low-flo shower heads, that amounts to 2.5 minutes. I see hot water in 20 seconds in my shower. The worst I have ever seen was 60 seconds in my previous home where the master shower and hot water heater were on opposite corners of a large ranch.
Quote:
Originally Posted by Arctic Fox
Don't forget that it is a waste of HOT water.
Once you turn your hot water tap off, you have five gallons of hot water in the piping, which will cool down and become the five gallons of cold water that you draw off next time.
Do you have space for a small water heater in your master bathroom? Doesn't need to be gas or "instant" - just a smaller version of what you have in your garage. Have another in your kitchen, and leave the main water heater off until you have guests.
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