Energy use of 80 gallon water heater
tupchurch
| Posted in Energy Efficiency and Durability on
Without getting a meter, is it possible to estimate the power usage of an HTP EVC080C2X045 in a household of 7? It’s a light commercial 80 gallon electric water heater with 4500 watt elements. I suppose being light commercial is why it doesn’t have an energy guide? I didn’t really know what I was buying and wish I had gotten a heat pump two years ago, but you live and you learn.
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Replies
You can buy a clamp-on watt hour meter on Amazon for about $20. That's going to do a better job.
That does seem like the easiest way to proceed. I had been thinking all or nothing with the pricey whole panel monitors, but this would be an easy step to take. Thank you.
You can calculate the amount of energy it will use to deliver a known volume of water heated a specified number of degrees. If, for example, you know you want 120 degree water, but you start with 50 degree water, you know you're heating the water 70 degrees. If you now now how many gallons you will need, you can calculate the energy needed to heat that volume of water by 70 degrees. The size of the heating elements in this case doesn't matter, their size just determines how quickly you can make hot water, which would limit how much flow you could get before the temperature would start to drop.
Standby losses are harder to estimate. It IS possible to calculate those if you know the temperature of the water in the tank, the temperature of the air around the tank, and the amount of insulation on the tank. It's probably not really worth trying to calculate that exactly though, since the energy used to make the hot water you use will likely be significantly more than the energy lost keeping the tank warm.
Bill
That makes sense and indicates why a meter is the only simple way to answer the question for my case. Thanks for your reply.
This type of meter is only $16 and seems to be pretty accurate.
https://www.amazon.com/HiLetgo-Multimeter-PZEM-061-Voltmeter-Transformer/dp/B079JNY5VD/ref=sr_1_13_sspa?crid=25X8IP35NFA7P&keywords=watt%2Bmeter&qid=1692954622&sprefix=watt%2Caps%2C152&sr=8-13-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&th=1
Walta
tupchurch,
It's worth remembering that all electric resistance hot water heaters are equally efficient. The only di9ffernece between them is the standby losses, so you get slightly cheaper hot water by buying something like this: https://www.homedepot.ca/product/rheem-marathon-30-gallon-114l-lifetime-electric-water-heater-3kw240v/1001105482?eid=PS_GOOGLE_D00%20-%20E-Comm_GGL_Shopping_PLA_EN_All%20Products_All%20Products__PRODUCT_GROUP_aud-1217348015026:pla-300587868876&gclid=EAIaIQobChMIue2_zpb4gAMVj9DCBB0n_gP8EAQYBCABEgKqkfD_BwE&gclsrc=aw.ds
I was surprised to see that the marathon has a lower UEF compared to some of Rheems other resistance tanks
Paul,
That is odd. I wonder why?
I can only guess less insulation?
Paul,
A big part of their marketing is the reduced standby losses due to more insulation: "2.5″ polyurethane insulation reduces heat loss for greater energy efficiency."
Also odd is the difference in both UEF and FRH between the Rheem branded Marathon units and the Richmond branded Marathon units, with the same model numbers.
The Richmond are rated 0.92-0.93, and the Rheem are 0.88-0.92, with the 100 gal 0.90 for both.
One of the companies is not telling the truth on their spec sheet.
UEF is based on energy output and recovery energy input for a prescribed set of water draw profiles over a 24 hour period.
Similar concept for first hour rating, but for 1 hour period.
Both UEF and FHR lower than steel tanks, so that's consistent with the test procedures.
Maybe the domed-end tank shape changes tank flow and stratification during the water draws in the UEF and FHR testing procedures....?
Maybe it's the heating element placement, knowing that the domed volume of water below the lower element isn't really heated properly, and that those domed volumes (above the upper element and below the lower) would be different for a given vertical element placement than a steel tank.
If it's less insulation: For 1 hour, how much additional standby loss is needed to change the first hour rating by such a large amount on the spec sheet?
Something is happening, and I'm completely unconvinced that it's related to insulation.
“ Paul,
A big part of their marketing is the reduced standby losses due to more insulation: "2.5″ polyurethane insulation reduces heat loss for greater energy efficiency."
Ha Malcolm, I’m shocked marketing copy isn’t truthful.
Life is disillusioning.