When gas wins over electric

Written by erin


Last weekend, I bought a new dryer. The old one was kaput, and though I wish it were otherwise, a clothesline doesn’t suffice for my family’s lifestyle. I started my quest with some virtual shopping. First dilemma: electric or gas?

Over the years I’ve always assumed “gas” because generating electricity by burning fuel and then making heat with the electricity is a very inefficient way to create heat. But the California electric grid has lots of carbon-free generation sources, so I decided to run the numbers.

To compare the greenhouse gas emissions of gas and electric dryers, we need a common denominator. Gas is measured in ccfs (hundreds of cubic feet) on my utility bill, while electricity is measured in kilowatt-hours. While these can be cross-converted, I decided to use BTUs as my common measure of heat. According to a handy calculator provided by the Energy Information Administration, 1 kilowatt-hour contains 3412 BTUs, and 1 cubic foot of natural gas contains 1027 BTUs. One load of laundry takes roughly 17,000 BTU to dry, and let’s assume 100 loads/year. So, how about those greenhouse gases?

For natural gas, we emit about 117 pounds CO2e per million BTU combusted (source: EIA). As explained in a recent post, the greenhouse gases associated with electricity generation vary with location, and depend on how the electricity is generated. The nationwide average is 1.37 pounds CO2e per kwh or 401.5 pounds per million BTU (source: EPA eGrid (.pdf)).

If you’re quick with numbers, you are already seeing that 401.5 is a lot more than 117.

Here in California, though, the grid is nearly the cleanest in the country with contributions from hydro power, nuclear power, natural gas, and an aggressive state law requiring renewables. Still, our grid calculates to about 200 lbs CO2e per MMBTU.

On an annual basis for dryers then, we have….

Gas dryer – 199 pounds CO2e
Electric dryer, California – 402 pounds CO2e
Electric dryer, national avg – 683 pounds CO2e

This made my decision really clear. Until the grid gets much cleaner, or until I employ enough solar panels to support all of my electricity use (including what would be a new demand from an electric dryer), natural gas is still the best way to create heat.

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  1. david

    The analysis in this article gives the impression that CO2 is the only factor to consider when considering the energy generation source of household power. While reducing all of these complexities to a single metric may address individual symptoms, they often fail to acknowledge the more complex root problems (in the case the *form* of energy generation). I’m disappointed to see such a reductionist approach to determining “efficiency” on Terrapass, particularly in light of documentaries like Gasland (http://www.gaslandthemovie.com) that highlight the extraordinary costs of natural gas extraction beyond atmospheric CO2 emissions.
    In the rhetorical extreme: If the least CO2 emissions were emitted from appliances that burn leatherback sea turtles, would they get your vote?

  2. Dave

    Be wary of propane dryers. I’m not sure how the CO2 stacks up when compared to natural gas, but my experience is that these dryers are less reliable and service people tend to throw up their hands when it comes to repair. Plus the cost of propane fluctuates roughly with the cost of gasoline so it can skyrocket and blow the cost analysis.

  3. Don

    A thoughtful comparison as far as it goes, but one thing really worries me about natural gas’s “CO2 advantage” currently being _heavily_ pushed nationally by America’s Natural Gas Alliance.
    When leaked unburned into the atmosphere, natural gas is more than 20x worse than CO2 for GHGs. That means that even a tiny fraction of leakage throughout the entire system negates the carbon advantage. And as you might guess, a nation-spanning delivery system with pipes into most homes leaks. (Anecdote: my neighbor’s house leaked gas for 14 years into a well-ventilated attic until he finally happened across the leaky pipe).
    My point: NG is neither the panacea the industry promo says it is, nor are the oft-cited reductions in CO2 over coal burning actually likely to be seen large scale due to leakage. Any analysis should include real-world leakage of unburned NG.

  4. AP

    Not environmental but a safety comment: Please have a professional install this! A family near where I live just had their entire house EXPLODE because the husband tried to DIY his new gas dryer. The couple is in serious condition at the hospital. The photos look like a warzone.

  5. Dave

    What would completely change this comparison is if decent heat-pump or condensing dryers were available.
    A heat pump dryer (uses a compressor like an air conditioner) would use about one third the electricity – in CA better than gas.
    A condensing dryer can be even better – instead of dumping hot air outside and reheating room-temp air back up, it condenses the moisture out and then only needs to heat the air up slightly – reusing all the heat that is currently thrown away. This could be applied to either gas, electric or heat-pump dryers.

  6. david

    for more on the hidden perils of natural gas: http://www.postcarbon.org/report/331901-will-natural-gas-fuel-america-in
    “Natural gas has increasingly been touted as a “bridge fuel” from high-carbon sources of energy like coal and oil to a renewable energy future. This is based on renewed optimism on the ability of horizontal drilling and hydraulic fracturing to access natural gas from previously inaccessible shale gas deposits. A review of the latest outlook (2011) of the U.S. Energy Information Administration (EIA) reveals that all eggs have been placed in the shale gas basket in terms of future growth in U.S. gas production. Without shale gas, U.S. domestic gas production is projected to fall by 20% through 2035.”

  7. Erin Craig

    Thanks David – I couldn’t agree more! I’m never able to expand as much as I’d like on a blog post. As usual, there is another “other side of the story” here in addition to the one you mention, namely all the non-carbon environmental impacts from electricity generation. Virtually every form of electricity generation has environmental externalities which neither the price nor the carbon footprint touch upon. Having said that, here in Northern California, the fossil-based fraction of our electricity is almost 100% natural gas, so comparing direct use of natural gas for heating to natural gas-to-electricity for heating, is a pretty fair way to go with respect to fugitive methane emissions accounting and other issues with natural gas extraction.

  8. Erin Craig

    Right! I for one am not a fan of advocating a natural gas “bridging strategy.” What we may have once thought of as a “bridge” creates its own momentum and before you know it, we’ve got such huge vested interests in that bridge that we can’t move beyond it. Still, I have to buy a dryer. While the California electricity grid is going to get cleaner (thanks to our global warming legislation), and at some point become the cleanest option for nearly every form of power or heat, that future is not here yet and won’t be over the life of my dryer. For the next few years,the tradeoff is natural gas direct use for natural gas-to-electricity – at least here in CA.

  9. Erin Craig

    Yes, I’m sure with a bit of product development or marketing attention there could be many better ways to get more dry out of less energy. Two related items… the washing machine I bought a couple years ago has a crazy-strong spin cycle. Clothes emerge practically dry to begin with; very cool. Also, I discovered that the latest thing in dryers is a steam cycle. Hello? Adding water to your dryer? Seriously? I stuck with a low-tech cheap model, no steam available.

  10. Barry

    A simple way to save energy is to remove your clothes while they are slightly damp and put them on hangers on a line or bar near the dryer. Clothes will also be less wrinkled and need no ironing.

  11. Eletruk

    You neglected to mention that many electric utilities now offer a choice of renewable energy. You can subscribe by percentage of generation source. I subscribe to 100% renewable energy, and it adds about 10% to my electric bill. So even though I live in the Pacific Northwest, where a large part of our electricity is already zero carbon (hydroelectric) I know that I am 100% offset with zero carbon sources.

  12. Gladwyn d'Souza

    We have a condensing dryer from Bosch. We use it in the rain of winter because our clothes line solar dryer is super efficient.. The condensing dryer takes a bit more involvement than a competitive energy hog.. The Air outlet needs to be cleaned once a year; probably quarterly, if used year round.

  13. Bryan

    Erin, I applaud you for making the effort to compare the dryer efficiencies. I wanted to check your calculations and searched for info on dryer energy consumption. I’m shocked at how little info is available that would allow an easy comparison.
    I think you’re in the ballpark. I also think gas might be more efficient that your calculations show because there are transmission losses along the electric power lines between the plant and your house and the electric heating element in the dryer is less than 100% efficient.
    To those who are *truly* using 100% renewable energy…good on ya. To those who think they are using 100% renewable energy but are really purchasing RECs for the equivalent amount of kWh, think again.
    To those who believe that gas is 20x the GHG threat than CO2, consider that if the gas weren’t leaked, it would be combusted. So The difference isn’t between fugitive gas and nothing, it’s between fugitive gas and combusted gas. And the difference reduces to about 7x. Certainly not good, but not as bad as you think.
    Finally, ask yourselves what is generating the electricity that you are using when you run your dryer in the middle of the night? Certainly not solar. Maybe not wind. Could very well be nuclear.

  14. Eletruk

    I’m not sure how you can say the heating element is not 100% efficient. Generally electrical systems inefficiency is the amount of electricity that doesn’t do the intended function (such as turn a motor or create light) that amount of function that didn’t happen is what get lost to heat. So if a heating element isn’t 100% efficient what amount of heat that isn’t generated is getting lost?