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Thread: Are electric water heaters safer than gas?

  1. #1
    DIY Member PM5K's Avatar
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    Default Are electric water heaters safer than gas?

    I have a friend that wants to install an electric water heater because he feels they are safer than gas. I can only speak from one experience in my life where a gas water heater caused a fire in a laundry room because clothes were left too close to the water heater. This was about twenty years ago so I don't know how the technology has changed, if it has at all.

    The only reason it even matters is that it seems generally speaking that gas water heaters are more efficient at putting out hot water, especially when looking at first hour delivery numbers, and recovery numbers.

    TIA

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    Plumber jimbo's Avatar
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    Electric water heaters are generally much more energy efficient, since a very high percentage of the energy used goes directly into the water temp. Conventional gas water heaters are much less efficient. BUT in many areas, due to RATES...gas is overall less $$$$ to operate.

    We have been living with natural gas in our houses for I guess over 100 years. Just like wood, or coal, or electric,....there is the potential for accidents, but with proper respect, I don't think you can make a case that gas is more likely to cause a fire than an electric.

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    DIY Member PM5K's Avatar
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    Yeah I noticed the actual energy factor ratings were better for the electric, but at the same time actual water delivery was lower, and here gas is cheaper than electricity.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    With anything in life, proper installation and maintenance makes a huge difference. Sloppy with the wiring, and you could electrocute yourself on an electric. Sloppy with the gas supply or venting, and you could either blow yourself up, or kill yourself from the fumes. CO detectors are a good idea anywhere there are burners. There are gas detectors, too, available. I've grown up with gas appliances, and don't know of anyone that has been hurt by one. Not to say that it can't happen. The current requirements for gas WH burners make it almost impossible to ignite vapors, or substances near them.

    FWIW, a gallon of gasoline has the equivalent energy of about 8 sticks of dynamite...do you avoid driving your car because it could blow up? Drive a new Nissan Leaf all-electric instead?
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Nuclear Engineer nukeman's Avatar
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    jimbo is correct. With electric, nearly 100% of energy goes into heating the water. Actually, 100% does go into heating the water, but then some of that is lost to the outside.

    With gas, you have to take the price per therm, figure out the cost per BTU, take into account how much goes up the flue, and then see what the equivalent rate is. Most people assume that gas will always be cheaper, but that is not always the case. Around here, the operating costs would be similar, but having gas would have an additional service cost, so unless other things in the house were also gas, that service cost would wipe out any savings.

    In addition, electric units are much easier to install and have other advantages. No vent pipe, no gas line, no worries on getting combustion air, no worries about combustion gases leaking into the home, no worries about gas leaks, etc. Because of this, you have more options as to where you could place the WH as well.

    Gas has a faster recovery, but that is just due to the size of the burner. You could get the same in an electric model, but the electrical load would be too much for most homes and the wiring to the WH would have to be increased to meet this load.

    Overall, electric would be safer, but there is nothing wrong with gas as long as the install is proper. If your friend has other things that run on gas, then there is no reason not to use a gas WH (assuming that gas is really cheaper and the gas line/vent are already in place). If the WH is the only gas device, then your friend would be better off by dumping the gas WH and going electric unless electric was much more expensive than gas.

    An additional advantage for electric is the operating costs are more stable. Natural gas prices can swing up and down much more than the cost of electricity. Serveral years back, natural gas was at record lows. A bunch of companies built a bunch of natural gas plants for making electricity. These plants can be built small and quickly and they thought they were getting a great buy. Of course, they were using the record low gas costs to figure operating costs and did not take into account the historically large swing in prices that gas goes through. Well, by the time they got them built (or before), gas went back up in price and the utilities couldn't afford to operate these plants except to cover peak loads. So, what I am saying is that even if gas is cheaper now, you should look back and see what prices have been in your area and think about what the prices might do in the future. When the price of gas is low, there is a good chance that it'll shoot back up.

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    Homeowner Thatguy's Avatar
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    Quote Originally Posted by PM5K View Post
    here gas is cheaper than electricity.
    How much you pay per kwh and per 100 cu. ft. of gas?

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    In the trades Dana's Avatar
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    The whole electric vs. gas "efficiency" is a bit bogus, since the actual efficiency depends on where you're measuring the input. With the exisiting ~30% thermally-efficient power grid, only 30% of the source-fuel energy arrives at the point where it's metered- 70% went up the flues and cooling stacked, and heated up the wires & transformers between the powerplant and the meter at your house. Once inside, the efficiency at the load (the heater itself) is pretty good. Electric tanks have inherently lower standby losses, but from a source-fuel POV it's EF is only 0.25 to 0.27, not the 0.92 or whatever it's test numbers indicate. If your local grid has a significant hydro or wind energy mix rather than purely combustion or nuclear generators you'll do better though. From a source fuel point of view, the lowly atmospheric-drafte gas tank heater is roughly twice as efficient as an electric tank heater(!).

    The lossiness of the grid is reflected in the price you pay per kwh- you're paying for that energy, one way or another.

    Gas heaters aren't "...more efficient at putting out hot water...", but they're more fuel efficient. More EFFECTIVE at putting out hot water would be a more accurate statement, but that is purely a function of how easy it is to apply the energy to the water at a high rate with a flame, rather than via the limitations of house wiring. With fat enough wires an a big enough transformer providing service to your house there's no theorectical reason why you couldn't crank as much power with electricity as with gas, but it would mean adding a ~30amp 240V circuit (and additional main-breaker capacity) forjust the hot water tank to meet the output of even the wimpiest gas-fired tank.

    Without open flame, flues, or combustion byproducts I s'pose its harder to kill yourself with an electric hot water heater. But a sealed-combustion forced-draft gas water heater would be inherently similar to an electric tank from a safety point of view.

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    Nuclear Engineer nukeman's Avatar
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    Dana: I agree, but remember that the NG isn't pumped from the well to your house without losses either. No free lunch. You would have to compare where the gas comes from and what it takes to pump it to your house vs. the losses for electric transmission/distribution.

    It really comes down to what works best for you. The gas does have faster recovery, but will you even need that recovery? It depends on your usage patterns, incoming water temp, capacity of the WH, etc. Electric is easier to install and probably easier to work on. There is much to them..just a couple t-stats and elements. Gas units are fairly simple too, but newer/more advanced models could encounter problems that might be harder for a homeowner to figure out.

    It really boils down to what was already there if it is a replacement unit. Going from gas to electric would mean capping gas lines, running new electric circuit, remove/cap vent. Much easier to just add another gas unit. Going the other way, you would have to add the gas line, vent, etc. (a bit harder to do in most cases).

    If it is a new house, then either one is just about as easy as the other. Electric would still be easier, but the difference isn't that much in new construction, especially if you have other things that will run on gas too.

    Besides the cost and other factors, it really comes down to how your friend feels about one option or another. Even if gas is cheaper/easier, it might not be worth it if your friend is constantly worrying about the place blowing up, burning down, or filling with NG or CO.

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    In the trades Dana's Avatar
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    nukeman, yes all grids have losses, but the grid losses of gas (even gas that's liquified and transported by ship, then pumped into a local grid) with rare exceptions, are typicall less than the fractional losses of electric grid transmission, and far lower than the losses at the generator. If that means your 0.58EF tank is truly only 0.50EF from well-head-to tank, it's still about 2x as source-efficient as an electric tank.

    But it doesn't much matter- doing the math on your actual water needs and actual utility rates will typically push you in the right direction. The safety of either are pretty high- that should be the least of your worries.

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    Moderator & Master Plumber hj's Avatar
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    Gas heaters are only dangerous if they have a leak, and a gas stove would be just as dangerous in that case. The new gas heaters are designed so that you can pour gasoline on the floor next to them without causing a fire, so your clothing could not do so either.

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    DIY Member PM5K's Avatar
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    As for the install, the house has gas and electric obviously, but neither has been run to the location of the new water heater because it's for a brand new bathroom. So in that regard there isn't an advantage either way, but when I think about it since he's paranoid, and since electric seems easier to install I'm leaning that way. I won't need a flue or whatever.

    Now I have to decide what size.

  12. #12
    Moderator & Master Plumber hj's Avatar
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    As an aside, back in the 50's the Southern States Plumbing code decided that electric water heaters were as "Safe as a lightbulb" and eliminated the requirement for a T&P safety valve on them. Every week after that the Domestic Engineering Magazine had a report of at least one electric water exploding demolishing the house and sometimes the neighbor's also. One particulary disturbing photo showed a young boy who was sleeping on the porch outside from where the water heater was. When it exploded, it decapitated him.

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    General Engineering Contractor ballvalve's Avatar
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    Luckily we now have a house full of T&P' valves - its called pex. That house was likely piped with hard steel everywhere.

    If I made water heaters there would be a "freeze plug" [opposite of] melting disc of metal somewhere under the insulation and shell for back up to the t&P.

    And of course electric is safer than a creeping invisible explosive. Especially Propane. Cheaper than Propane too.

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    Propane is heavier than air, and will fill up a closed space from the bottom up. NG is lighter than air, has a pungent smell added to it and disperses throughout the open area. You are much more likely to notice a NG leak than a propane leak. Plus, the pressure from a failed regulator (not all that common to leak outright into the room) has the system pressure much less with NG. A venting propane tank can function like a rocket bottle, since the pressure can be quite high...it makes a pretty good blowtorch as well.

    All that being said, I would say an electric appliance is less complex (not by much) and potentially safer. But, a failure in either delivery can be fatal - electrical via electrocution and potentially fires; gas by explosion. Either can kill you, and neither will necessarily give you much notice. Any WH could potentially explode on its own if the safety features were defective along with some other failure, as steam explosions are often rather catastrophic.

    There was a gas explosion in the Boston area this week...nobody was hurt because nobody was home. A contruction company accidentally pulled the gas meter off the house, and it ended up filling the house with gas. Not a faulty installation, just careless construction worker (hope they have good insurance the house was worth over $1M).

    A NG detector isn't a bad investment whenever you are using that fuel. But, once installed properly, lines and appliances rarely leak on their own enough to cause any damage unless something is done to them.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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