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Anyone use an IR electric tankless water heater?

Irishjake | Posted in General Questions on

I’m just not sold on installing a standard electric water heater for my one bedroom apartment above our detached garage. It kills me to think that I’ll be heating water all day, for use only a couple times a day. The fact that conventional water heaters don’t last long and get all scaly perturbs me too.

I recently stumbled across a IR Electric Tankless Water Heater by SuperGreen
it sells for $464 on Amazon, which is two hundred less than the Bradford White 38 gallon Water Heater I recently spec’d. This model I thought would service a shower, sink, washer and bosch dishwasher. I’m in Zone 6a (Central NH), and our incoming water temp I think is about 47F.

The SuperGreen IR14220 requires a huge amount of amperage (60!!!!), but I’ve got a 400amp service and I’ll have 18kW of PV up and running soon. Trying to decide if it’s going to save money, and maintenance?

Supposedly, because the IR doesn’t come in contact with the water, it keeps the mineral buildup and other such maintenance headaches to a minimum.

Any thoughts?

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  1. GBA Editor
    Martin Holladay | | #1

    The word "infrared" in this company's marketing materials (and the use of the brand name "SuperGreen") are nonsense, so that makes me irked at the company right away. This is an electric-resistance tankless water heater. Well-known brands include Stiebel Eltron.

    Electric-resistance tankless water heaters sometimes make sense. The big disadvantages are (a) high fuel cost, and (b) the need for a electrical service with an unusually high amperage, which can mean expensive rewiring or the need for a big service panel, and (c) the tendency of these units to contribute to high peak loads (a problem for electrical utilities -- and a problem that undermines the "SuperGreen" idea).

    For more information, see Domestic Hot Water: No Perfect Solution.

  2. Expert Member
    Dana Dorsett | | #2

    The notion that you will " heating water all day..." with a standard electric HW heater is unfounded.

    A more accurate description is the would be storing hot water all day, and only heating it once the temperature in the tank dropped sufficiently. If you're using it a couple of times per day it means you'd be heating it only after a significant draw of hot water, since any electric tank sold in the US today has very good insulation levels, and heat traps on the plumbing connections, which reduces the standby losses to miniscule levels.

    Mineral build up is a function of what's in the water as well as temperature. If you're heating it up to typical domestic hot water temperatures, you can bet that it will develop lime & scale deposits. But unlike with a tank HW heater, mineral deposition inside flash heaters can build up to the point that it restricts flow, which is a common maintenance issue with ALL on-demand tankless HW heaters- this one is not immune!

    A 14 kw tankless in zone 6A NH is barely enough to support a low flow tepid-temperature shower in mid winter. The average annual incoming water temp might be 47F in your location, but unless you're on a volcanic hot spot or something you will definitely be seeing mid to late winter water temps dipping below 40F on occasion. In mid to late summer the incoming water temps will be in the 50s F, which is about the only time of the year a 14kw tankless would provide anything remotely esembling reasonable hot water service. Even a 20 kw tankless is pretty marginal in your location for wintertime use. A 2.0 gpm shower with 40F incoming water and 105F at the shower head takes about 19kw. A full flow 2.5gpm shower is close to 24 kw. Filling a bathtub with 110F water at a reasonable rate takes a heluva lot more than 14kw.

    Electric tankless water heaters are also huge intermittent loads, loads that stress the grid infrastructure when used during grid load peaks. Just because you have a 400A service doesn't mean it's going to be "green" to actually use that. If residential rate structures change and "demand charges" are applied to reflect your peak grid draws (as is starting to happen with solar ratepayers in some areas in the southwest) the thing could end up costing you money. I'm not sure how likely a change to demand charges rather than flat energy metering is in NH or with your utility, but the whole electric utility business is in a rapid state of flux, with a lot of pressure on regulators to ensure that solar ratepayers are paying a "fair share" for the grid infrastructure that is being used rather than cost-shifting the grid capital & maintenance costs onto non-solar ratepayers. Many of those arguments by utilities are thinly veiled attempts by utilities to preserve & protect their revenue streams, but the fairest way of valuing distributed solar or the grid is far from settled. Charging people with large intermittent loads for the "fair share" of the infrastructure required to support those loads is definitely becoming part of the rate case discussion.

  3. Irishjake | | #3

    Dana thanks for putting it into perspective. I had given up on tankless electric water heaters for my DHW for all the reasons above, and happened upon this supposedly greener and much more efficient technology. I wanted to ask about it and see if it the IR technology truly made it more efficient, and maintenance free. Thanks for clarifying.

  4. Lidkeeper | | #4

    I have tried tankless electric with elements and it's a nightmare. I went with a natural gas unit and I love it. I have been reading up on these ir units and they seem to be what I want for a replacement for a leaking propane tankless(no natural gas available) at my other residence. Hard water is a problem for my area and even the natural gas one has to be flushed about once a year. So to have one heat in the way they do that there is no scale buildup and no elements to go out is an exciting thought for me and definitely will be my next option. The company seems to stand behind them and that's good but I hope to not have any problems.

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