natural gas vs. electric water heater

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Daddy_cat, Dec 27, 2005.

  1. Daddy_cat

    Daddy_cat New Member

    Dec 27, 2005
    I need to add a water heater for our new addition. Natural gas has always been the 1st choice for heating appliances because it cost less to use (in the Southeast part of the country), but with the increase in price expected, would it be worth the extra cost of the plumbing and the water heater or would it be better to install a high effeciency electric water heater? (It will be going in the attic)


  2. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    Start by looking at your gas bill and your electric bill to find the rates:
    Cost per kWHr of electricity and cost per therm of gas.

    One therm is 100,000 BTUs which is energy equivalent to 29.3 kWHr, but you aren't done yet because of different efficiencies.

    Electric water heater losses are essentially only the heat loss from the tank. You will not be far off if you use 96% efficiency. Gas water heater efficiencies vary more depending on whether you have a condensing unit or a standard heater. I haven't looked them up but they are probably in the range of 70 to 95% depending on the unit.

    For your 96% efficient electric heater at $0.10 per kWHr it will cost you $3.05 to get 100,000 BTUs of usable hot water. To get the cost in your area, adjust by using your electric rate.

    If gas is $2.50 per therm and your gas water heater is 85% efficient, then it will cost you $2.50/0.85 = $2.94 to get 100,000 BTUs of usable hot water. Again, adjust by your rate and efficiency.

    An alternative for long distance water heating, if you have an adequate and efficient gas water heater in your house, is to put a small local heater at the distant location and feed it from the gas water heater. Something like the Ariston GL2.5 operates off a 115 Volt circuit and will supply all you need for the lavatory or sink flows, and the gas water heater will make up the hot water demand for showers and other larger uses. It doesn't eliminate all the pipe heat losses but it avoids people running water down the drain to get hot water out of the faucet.
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  4. Daddy_cat

    Daddy_cat New Member

    Dec 27, 2005
    Thanks! I'll get the calculator out......
  5. plumber1

    plumber1 Plumber

    Aug 7, 2005

    You calculate, I'll do the gas heater........
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