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Question DetailsAsked on 2/26/2018

What do you need to consider when replacing conventional water heater to tankless?

Cold winter climate (UT), 2000 sq ft house, single family of 1 person

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1 Answer


I would not call your area "cold winter" unmless up in the cold parts of the Wasatch Range or east of SLC or far northern part of the state, but here are a couple of previous questions like yours with answers, FYI:

Primary decision considerations:

1) this is commonly the first complaint - having a high enough hot water throughput (at the desired output temp rise through the unit - so for a given output tempt the colder the input temp with cold ground temps like yours, the bigger capacity you need) - in a one person house the issue of competing demand does not come into play (like two showers going at a time), but you need to consider what washer or dishwasher or shower/tub flow rate and total heating over a period of time you need, especially if you use a shower head which is not energy-rated down to 1/2 gpm or such.

2) are you going to religiously clean it as required so it does not crud up - and if your incoming water (after any water softening) is mineral rich, pretty much guaranteed to be a major problem unless you also put in a demineralizing unit before it

3) energy costs, especially if using electric - for high throughput rates they are real electricity hogs in normal or high cost electric areas

4) cost - typically the units cost twice or more, installed, what a normal hot water system does

5) does it have to handle hydronic heating load as well as domestic hot water - in hydronic heating service they require a lot oif ancillary plumbing and controls to put out the high-temp water needed for the heating system and also the domestic "warm" water - and some units do it by blending heated hot water with cold water for the domestic water, which can be a bit of an energy waster

6) practical life - lots promise 15-30 years, from what I have seen several to MAYBE 8 or so is more normal

7) assuming this is a house in more or less constant use, are the energy savings (if any) going to be anywhere near the added cost. Can be better economically with a house vacant much of the day where hot wate demand is small and concentrated in a short timeframe each day, less so if in use day-around. Can also make sense in a cabin environment where the demand is zero for extended periods - though in that case the units tend to crud up with precipitates too.

8) commonly with gas service, and almost certainly if electric - your in-house service lines will need to be upgraded, and while with gas usually the meter has enough throughput capacity, it is not at all uncommon to require major electrical upgrades, including commonly to the incoming utility service drop as well, to handle the high surge loads of the unit

9) if you are on time-of-day utility pricing, that can have an effect too - conventional water heaters with an energy timer on them can store that hot water for use when wanted, not so with tankless, which tend to get almost all their usage demand during peak utility rate periods.

10) how long are you pretty much certain to stay in that place - because with the high cost of installation if you do not stay for at least the normal life of the unit you will not have any chance of recovering its higher cost, and buyers do not pay a premium for that sort of item in most cases. In fact, like hot tubs and pools and such, tends to be more of a turnoff than a benefit to have it come resale time.

11) is the company selling it going to be around in a few years to honor any warranty - and if around will they stand behind it. Also, many manufacturers require that the unit be serviced every 3-12 months by a firm THEY approve - so tends to be, in many cases, the BMW or Porsche effect - few authorized maintenance/repair people, who tend to overcharge because of that monopoly. In our area there is a popular brand which I have heard local authorized plumbers charge about $500 for a 1 hour servicing and cleaning - because the market will bear it.

As you can probably tell, I am no fan of them - not only do I think they are not up to snuff yet from a technological standpoint, but I feel they are generally overpriced - and plumbers tend to mark up the unit price and chrage a lot more for installation than is fair in many cases. Perhaps due to the "greenie surcharge" - many contractors (and repairmen and such - look at imported car repair costs) - tend to significantly bump up the cost of "environmental fad" items like this, figuring if the person is committed to getting it for environmental purposes (because tankless heaters are rarely anywhere near econolmic by themselves) then they are prepared to pay a nice premium for it. I have seen a number of $1000 tankless units (retail price if you bought it yourself) end up costing the customer $10,000 and more. Takes of LOT of years of savings (if there are any) to pay for that.

Here are a couple of additional previous questions on installation issues for tankless heaters FYI:

Answered 2 years ago by LCD

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