Tankless Hot Water

Steve_Slota

Good morning. I am at the point now where I will need to change my hot water tank in the basement. I currently have a 40 gallon hot water storage tank which is heated by my boiler. I am really interested in changing to an on demand tankless hot water heater. Being that I am more than likely converting to solar power, I was contemplating going with an electric on demand heater. My current fuel source for hot water and heat is LP.

Looking for some pros and cons for electric vs. LP tankless water heaters.

Have a great day all!

Zman

The biggest drawback with electric tankless is electrical requirements. They tend to be huge.
If you were to compare a typical 200,000 BTU/hr input propane model at 85% efficiency, it would have a 170,000 BTU/hr output.
To get that same performance out of an electric model, you would need approx 50KW/hr.
In a typical home with single phase power that would be about 208 amps. Most residential homes have an electrical service of 200 amps or less.

Larry Weingarten

Hello: If you're going solar and tankless, you need to find a unit that can heat only a little. That is if the solar is giving you 100 degrees and you want 105, will your tankless be able to heat that little amount? I agree with Zman, yet electrics do have the ability to do only a little heating, where I don't know of any gas units that can. Another way to go is by using a unit with small storage and large burner, like the Crossover by HTP. With its 20 gallons of stored water, it can have simpler controls and deliver hot water faster than tankless.

Yours, Larry

Zman

Hatterasguy said:

Zman said:

To get that same performance out of an electric model, you would need approx 50KW/hr.

50KW

KW is a unit of power, similar to BTU/H.

KWH is a unit of energy.

KW/H has no useful meaning.

Counter intuitive but true.
And I though I wasn't going to learn anything new today....

njtommy

How about a heat pump water heater?

cableman

Best thing i did was remove my boilers tankless coil and install a heap pump hot water heater. I used an 80gal ge geospring but ge is going to stop making hpw heaters now. There are other company's though.
Id say it raised my electric bill 10-12 bucks a month.

bulldoglax

Couldn't agree more with the heat pump option, most states in the north east have substantial rebates. If you have 750 cubic ft of ambient air and a basement that stays above 50 degrees in the winter it should operate in its heat pump mode and be very minimum cost to operate.

I would stay as far away from electric in demand, depending on you location and ground water temps if you have a 70 degree delta t you could be flowing low gpm and also drawing well over 140 amps. I don't know a ton of folks who have room in their electrical panel for an additional 3-4 two pole breakers.

Rinnai has a very nice propane tankless options and honestly your current setup if an indirect might be one of the most efficient set ups out there.

I would get quotes on heatpump, propane tankless and a new indirect

SWEI

Solar thermal still makes sense for domestic hot water in much of the country. Post-heat for that is one place where we regularly specify tankless electric heaters -- they modulate to near-zero, unlike anything that is gas-fired.