What’s the best way to save energy used for hot water?
So I’ve collected a whole bunch of information about my existing water-heating situation, but I’m having trouble working out how to compare the cost/benefit for ways to save energy. I’ll detail my existing situation first, and then list the options I’ve come up with. Any clarification will be greatly appreciated!
I live in Northwest Connecticut in a house with a damp, unconditioned, uninsulated, 950-sq.ft. stone basement containing no mechanical systems other than our 12-year-old 50-gallon GE electric water heater (w/ 4500-watt and 3380-watt coils). When it’s around freezing temperatures outside, the basement is about 50 degrees and the incoming temperature of our municipal water supply is in the low 40s. Our shower runs for a good half hour per day (at about 110-degrees), and is directly next to a 4-inch vertical PVC drain that runs directly down to about where the water heater is in the basement. I have to run a dehumidifier all summer to keep the basement at a bearable level of humidity. My house is 100% electric, with Mitsubishi mini-splits for heat, and I just got a 10.2kW grid-tied PV system installed.
So so I figure that I have a few options, and may even choose to implement more than one over time, but want to try to do the one with the biggest ROI first.
1) I could I nstall a vertical 4”x48” DWHR device between my shower and my existing water heater. While repairing a blocked drainpipe this week, we were unable to use any hot water, and I saw my electricity use drop by what would amount to $2 per day, and that doesn’t even account for the rate hike we’re getting in CT next month. With the high price of copper, a DWHR would cost me about $1000, but I would install it myself. I found some charts and calculators online, and roughly figured out that my shower is possibly(?) using 64,000 BTUs per hour, and a DWHR in the size I’m looking for could recover 33,000 BTUs per hour, but I don’t know if the recovery time can be compared apples to apples to the time it takes to bring the water heater back up to temperature.
2) I could install a heat-pump water heater. I have friends with similar old stone basements who have seen huge savings with a heat-pump water heater, but they also have an oil furnace, so their basement is quite warm. I wasn’t sure if my 40-50 degree basement would be warm enough, and if it would just be stealing heat from my house above. I do like the idea of the bonus dehumidification in summer though.
3) I could insulate my water heater and/or build an insulated enclosure for it. Right now my water heater just sits on the concrete floor of my cold basement. I imagine just placing it on some rigid foam could help a little, but I would be willing to build a small closet insulated on all sides to contain my water heater. Alternatively, how can I tell if it’s safe to just add an insulating blanket just around the water heater itself, and would that make a difference?
Which option seems like the best investment? Are there any options I haven’t thought of?
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