How much will a tankless water heater save over a gas water heater : LUSENET : The Plumb Truth : One Thread

I'm toying with the idea of a tankless water heater for my 4 br 2 ba house. Any body know how much it will save in utilities in So. Cal. I think I'll need a 4.5 - 5.0 gpm model. Also, does it make sense to switch to an electric tankless. I currently have a 40 gal quick refraction gas tank water heater that's only about 2 years old. The 40 gal is barely enough, I should have bought a 50 gal, but was told the 40 gal quick refraction would be enough. Sometimes the shower is not hot enough if we've done the laundry or run the dishwasher prior. Thanks for your input.

-- Glen Beer (gbeer@charlesdunn.comm), October 03, 2001


I'm not going to take the time to run the calculations but, it;s easy to exceed 5 gpm. of flow in a typical home. Washing machine, shower and and washing the hands will get you to 8gpm. potentially, and a cold blast in the shower. To get a 50 degree rise at 8 gpm. requires 200,000 btu. of heat(just a wild guesstimate). Add a furnace and you'll need a flue sized for 350,000 btu. Anyway, the best way to use a tankless water heater is to pipe it in-series before the tank water heater. The only practical reason to do this is for space concerns. A tanked h/w/heater is $150, tankless $500. It could take 10 years to recover the cost through effiency. By that time you'll need to replace the tankless anyway.

-- Tom Sidla (, October 06, 2001.

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