Any advice on tankless hot water heaters in cold climates?

Hi All,

I'm interested in getting an electric tankless hot water heater to save electricity. My concern is that I live in a cold climate and ground water temperature can get down to the 40's. Does anyone know if an instant electric model is usable under these conditions?

For reference, I'm looking at the PowerStar AE125 at Home Depot.

Thanks,
Robert

It's interesting how often this stuff comes up in conversation around here

I'll see if i can't sum up some of what I've learned in the past from looking at these things.

The lower power ones simply dont work well enough from what I've heard, people are not happy with the smaller models except for under the sink use, but for bathing at all you'll want the bigger ones or they just dont make enough water.

Then you need to figure out if you even have the power available to run one. Even a smaller one can use 60 amps and the bigger ones can run up to 100amps! If you only have a 100 amp service you can't have one. Even if you have a 200 amp service you might not have the capability to run one and running electric service to them isn't as simple or as cheap as plugging them into an outlet, you have to run multiple 30 or 60 amp lines to them from multiple breakers increasing the installation costs. The gas powered ones have the same problem, you need bigger than standard gas pipes run to them as they use so much and you may even need to upgrade your under ground service in some areas as there just isn't enough gas pressure available to run them.

As far as if they make sense to save money, it depends on your usage. If you need a LOT of hot water (say multiple teenagers all showering in the morning Then they can make more hot water than a tank, but you'll b e using so much of it that it wont save you much if anything. My mom has one in the visiting grandchild rooms of her house, so perhaps 9 months out of the year it gets no use at all, saving them money over keeping the tank hot that whole time, but when we are visiting it gets used a lot. A situation like that it will save you money. But you wont necessarily save any just by replacing a tank in a regular household. You really need to do the math on your usage and your electric rates.

Which brings up the last issue to check, many areas bill electric usage more for peak usage. So the more power you use at once, the more you pay for it. Check to make sure you dont have a peak electric meter.

Hi James,

Wow! Thanks for the very comprehensive and informative post! I really appreciate it. The first thing I'm going to check is if my house (I live in an older house) can even accomodate the power requirements. Also, your points about usage make a lot of sense as well.

Thanks again!

Best,
Robert

I am not sure that it makes sense to ever have an electric tankless hot water heater...

As James typed, besides all of the issues of installation--there is one big problem that I have only seen mentioned in one other place... That is the electric tankless water heaters control their temperature by rapidly cycling on and off... In many homes (if not all), causing the lights to dim and brighten repeatedly--very irritating.

I would humbly suggest to simply insulate the heck out of an existing electric hot water heater (including the water lines and T&P valve). Electric hot water heaters already have very high efficiencies (no central stack and pilot light like a gas hot water heater)--so a tankless one does not really save anything much.

And, if you can get Time of Use metering, you can heat your hot water off-peak and draw from the tank only during peak hours (for me, my summer peak/off-peak rates are $0.29/$0.09 per kWhr... The standard rate is $0.114 per kWhr. Winter peak/off-peak rates are $0.11/$0.09 per kWhr). My peak times (there are several TOU planes available) are Noon-6pm Monday through Friday. So--not too hard to avoid peak usage (I have gas myself). Cost me $277 for the meter and installation (there may be a one year minimum contract also--after that you can change back anytime if you wish).

There is a way of getting hot water for much less money (ignoring installation costs)... Some heat pump systems can also supply domestic hot water too.

And, you can go further and install a geothermal heat pump (uses local water pond/river or buried in soil heat exchangers). Very popular in parts of the US right now (to the point that, from what I have read, that it is hard to interest a contractor in working on a residence right now--with all of the commercial work going on right now).

Lastly, if you have the ability to use Solar--then you might wish to look at solar hot water--In theory, solar hot water uses less roof space, costs less to install, and has a better return on investment than solar electric systems (I am looking at doing solar hot water--but I don't have a good place for the solar water panels right now, I already have installed a Solar PV Electric System--plus, many systems seem to demand quite a bit of maintenance and extra space—several reasons why I am still looking myself).

-Bill

Hi Bill,

Thanks for all of the info! I am especially interested in geothermal heat as I've read that in the summer, hot water is a "free" byproduct. Do you know if geothermal systems have been effectively used in cold climates like upstate NY? We have very cold winters, but when I build a new house, I would love to have a system like that.

Thanks,
Robert

You might want to check out these threads:

Tankless water heaters?

Water Heaters

-john

I don't really need AC here, so I don't have any real experience in this area. But using the buried heat exchanger is supposed to allow good functioning in winter or summer as the soil, more than a few feet deep (in most areas) has a pretty constant temperature.

From what little I have read, I would suggest that you google the web and news groups for specific manufacturers and installers... There are folks that are happy with their installations, but it also sounds like there are some companies that are related to the aluminum and vinyl siding contractors of times past (for those of you youngsters out there—that is not a good thing).

Again, from what I have read, if you decide to go geothermal with the ground/well buried closed circuit heat exchanger, it sounds like they need to dig up more or go deeper/more wells than what is described in the glossy brochures as a "few loops of pipe or a couple wells".

-Bill

I have a gas one. It works well you can take a shower all day long etc. The only problem is that you have to wait a few minutes for the hot water to flow. So if you want to wash your hands then you have to get used to doing it in cold water or wait a couple of minutes. This is very annoying and I wouldn't have gotten one if I know abut it I wash my hands many many times a day but I only take one shower.:thumbsdow

I can offer specific advice.

I used a 120 amp model, 28.8KW. It made enough for 1 shower when ground water was that cold. You might be able to run a faucet also, but anything over that would start to kill the output temp.

Large electric models WILL cause your lights to flicker. I don't care what you do. The details we tried are too numerous to mention, but we tried them all.