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  1. #1
    Join Date
    May 2013
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    3

    Default Tankless water heater question

    I am thinking about replacing my 50 gallon gas fired water heater with an electric tankless. What brands, BTU's, etc would you recommend? Is this something I can do myself or should I use a professional?

  2. #2
    Join Date
    Oct 2012
    Location
    Houston, TX
    Posts
    295

    Default Re: Tankless water heater question

    If you do not have confidence in electrical work you will want to hire a pro as you will have to run some heavy gauge electrical line to the location of the water heater.

    To calculate the size of the water heater needed you will need to provide some info like the number of bathrooms it supplies, the number of people in the house, are there any tubs?

    List out all of your hot water demands so you can calculate your need.
    It's this old house, not this built after your dad was born house.

  3. #3
    Join Date
    Jul 2010
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    SoCal
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    6,480

    Default Re: Tankless water heater question

    Just a question: why do you want to change from natural gas to electric? did you win the lottery?

  4. #4
    Join Date
    Dec 2007
    Location
    Tennessee
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    1,730

    Default Re: Tankless water heater question

    This is a hot topic for me. Electric tankless water heaters should be banned from the market place. At the very least, people who get them should be primary metered by the utility company.

    Primary metering is where the meter is attached to the primary side of the transformer instead of the secondary side. This is often done for commercial customers. The difference is that with secondary metering, the utility pays for the transformer losses. On primary metering, you pay for the transformer losses.

    An electric tankless water heater causes the transformer losses to skyrocket. If the utility does not change your transformer, it will be too small to provide all the current that these need and still power anything else in your house. You will have a brownout every time it kicks on. During this brownout condition, the load losses in the transformer will be through the roof.

    To meet the needs of a tankless water heater, and the rest of the house too, the utility would have to install a much larger transformer. This not only costs the utility more up front, a larger transformer has higher no-load (aka core loss or iron loss) than a smaller one, and those losses are 24/7.

    In addition to the larger transformer, you may need larger wires from the transformer to your meter, another additional cost. Some utilities may not install a larger transformer.

  5. #5
    Join Date
    May 2013
    Posts
    3

    Default Re: Tankless water heater question

    Understood. It's a two full bath ranch house. We have a 10yr old washer and only two people living at the house. So not a ton of demand.

  6. #6
    Join Date
    May 2013
    Posts
    3

    Default Re: Tankless water heater question

    Quote Originally Posted by dj1 View Post
    Just a question: why do you want to change from natural gas to electric? did you win the lottery?
    I did not, lol. I understand that electric is lower cost to operate v gas. Is this a misconception?

  7. #7
    Join Date
    Jul 2010
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    SoCal
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    6,480

    Default Re: Tankless water heater question

    Quote Originally Posted by CincyDave View Post
    I did not, lol. I understand that electric is lower cost to operate v gas. Is this a misconception?
    NG (natural gas) is not only cheaper than Electricity, it also pollutes less and costs less. You see, the electricity in your house has to be produced someplace - at a power plant, and that's where it creates its pollution, mainly from burning coal.

    So while NG prices fluctuate a little, Electricity prices only go up, year after year, making it a very poor choice for heating water for example.

    And one day, Solar power will be so sensible, that it will shut down power plants. I can't wait for that day.

  8. #8
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,591

    Default Re: Tankless water heater question

    Quote Originally Posted by CincyDave View Post
    I did not, lol. I understand that electric is lower cost to operate v gas. Is this a misconception?
    Really, it depends on the electric and gas utility rates where you live. In the northeastern states, electricity is considerably more expensive than gas. In parts of the northwest, electricity will be cheaper than gas. My brother who lives in Clatskanie, Oregon heats his entire house with electricity (and not a heat pump, either) because it's far cheaper than any other energy source available to him. (Clatskanie has among the lowest electric rates in the nation.)

    That said, the total energy usage of an on-demand water heater will be lower than a storage-type water heater, because the storage heater will expend energy keeping the water warm even when it's not being used whereas the demand heater will not. Further, an electric on-demand water heater will use less total energy than a similar gas unit due to flue losses with the gas. But that's total energy, not total cost. You need to compare the cost per standard unit of energy to understand the actual cost of operation. Don't judge by the EnergyGuide label, because those are based on average costs of energy, not the actual cost in your area, so they may not present an accurate comparison between the operating cost of electric vs. gas.

    I have to concur with keith3267. One major reason that electric companies provide energy efficiency credits, besides government mandates, is that it's cheaper to pay for efficiency than build new power plants. However, while on-demand electric water heaters may be more efficient over a long period of time, their peak energy demand (how many watts they need at any given time) is much higher than for a storage-tank type water heater. Power plants, substations, and lines must be built to accommodate peak demand rather than average demand. That means if everyone switched to on-demand electric water heaters, utilities would have to build more power plants even though the total fuel consumption of those plants may be less.

    Even natural gas facilities could be impacted by the use of on-demand water heaters (though I do not know to what degree). You can only force so much gas through a pipe; compressors can only pump so much gas into the system.

    As for solar and wind power sources, those cannot be relied upon as the sole energy source (at least not until we can build high-density, efficient electric batteries) because they are weather dependent. It doesn't matter how much wind and solar facilities you have, you still need to build traditional hydro- or fuel-powered facilities to meet the demand during times of insufficient wind or sun. With a large enough power grid you may be able to generate some of the demand all the time, and all of the demand some of the time, but you'll never be able to generate all of the demand all of the time with only solar and wind.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  9. #9
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,730

    Default Re: Tankless water heater question

    If you a gas water heater and want to go with an on-demand, by all means do so with a gas unit, but do not go with an electric on demand. You will not like it and your utility company will not be happy with you getting one either. They are major headache for utilities.

    When you see how on demand electrics affect the transformer losses, you will see that they are actually less efficient than a tank type electric.

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