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.