How to Choose an Electric Water Heater
user-5378275
| Posted in Energy Efficiency and Durability on
I’m looking for an electric hot water heater that is efficient and not too expensive. Not interested in heat pump type, just basic efficient model. The two suppliers we deal with use American or AO Smith. Any thoughts on these? Any other brands? Thanks, Ben
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Replies
Ben,
When it comes to fuel use, all electric-resistance water heaters have the same efficiency (100%). That means that 100% of the electrical energy is converted into heat.
Electric resistance water heaters receive an EF (Energy Factor) rating; these EF numbers are all above 90. They vary depending on the thickness of the insulation; thicker insulation results in a higher number. So if you want high efficiency, choose a model with a high EF. Most of these appliances are very close in performance.
Are there other conisderations for durability and longevity? element type?, tank construction?
There is nothing to distinguish between brands/models of standard electric HW heaters sold in the US in terms of reliability. A $99 hardware store special lasts about as long as a $299 box store special or a full-retail $529.
They typically come with either a 6 year or 12 year warranty (some have 9 year versions). It's the same hot water heater in every respect except that the 12 year warranty version has a sacrificial anode, whereas the 6 year unit does not, with a plug at the anode port. The anode only comes into play only AFTER the glass liner has been compromised, and it slows the rate at which the steel portions rust out & eventually leak.
Ryan,
If price is no object, you might want to choose a Marathon water heater. Marathon water heaters have a polybutylene tank. These tanks can't rust, so they aren't likely to leak. Of course, Marathon heaters cost more than heaters with an enameled steel tank.
The Rheem Marathon is great. I have an 85 gallon for my all-electric house. It is EF .95, and the tank has a limited lifetime warranty. But it is expensive at more than $1,000.
The Marathon is great, but probably fails the "... and not too expensive... " test.
thanks all, very helpfull
Older post, but same subject so I thought I'd tack on to it. I had an 85 gallon Marathon in the house I just sold for 10 years, it was great. For the home I'm building, I'm tempted to go with a Heat Pump water heater to potentially save $30 a month; my concern is the noise. The house will be a rectangle, 30' x 66', basement will not have support beams so it will be open (web truss for the 30' span). If I went with another Marathon and added drain water heat recovery (any brand recommendations?) to recover some of the heat to the cold water inlet of the Marathon, what kind of reduction in costs could I expect? Probably difficult to quantify without actual hard numbers, which I don't have. I can say 2 adults and 2 children, and the majority of hot water used was for showers. I don't believe I could get the operating costs down to the HPHW, but if I could knock off 20% I think I would stay with the Marathon.
The amount you save with drainwater heat recovery depends a lot on your hot water use and showering times. Typical savings might be 20% for a 3-4 person family taking daily showers, but effectively zero for tub-bathers, and maybe even 50% for shower-hog families that like to stay in the shower until the water runs cold.
This guy's set o' marketing slides claims "Saves customers up to 35% on water heating costs (for 54% eff unit) ", efficiency tested per the NRCAN protocol:
https://www.resnet.us/uploads/documents/conference/2012/pdfs/Buchalter-Drain_Water_Heat_Recovery_Systems.pdf
Renewability's PowerPipe series units have lower pressure drop across the heat exchanger than most of the competition. At least pointy-nosed inspector in Michigan condemned a PowerPipe installation though, since the tubing used for the brazed manifolds is heavier than the stuff used in standard potable piping, and doesn't have the ASTM B88 stripe marking it as potable tubing, even though it's the same alloy, albeit at a heavier wall thickness than is covered by ASTM B88. But PowerPipe units are listed as a pre-approved fixture in Massachusetts (home of one of the pickier state plumbing codes) despite the lack of the stripe. Before installing ANY drainwater heat exchanger make sure the inspector is on board with it, since it's just non-standard enough that some are going to look for ways to disqualify it.
Full disclosure: I have a 4" x 48" PowerPipe installed at my house for going on a decade now. It works. I haven't instrumented it or rigorously tested it's in-situ efficiency. I'm just a satisfied customer, with no financial interest of any type in that company.
Thanks Dana,
My wife is in the "30 minute shower" club (not always, but sometimes) so it sounds like it would work well for us. Can you get by with a smaller water heater then? Of perhaps, if I recall correctly, most electric water heaters have two elements, a high and a low wattage element, disable the high wattage element. Slower recovery but less power consumed?
Power is Power; disabling the 2nd element will just slow recovery times. If you want efficient, get a HPWH. They're not that noisy! Less than a small AC. They run a few times a day. You can set them to only run at night, or if that disturbs sleep, to only run during the day.