Lately I’ve been working on my presentation for the 10th anniversary of the North American Passive House Conference. It’s on the global warming impact of insulation, a followup to my latest article about Alex Wilson’s work on that subject.
One of the things I wanted to do was to see what difference it made when a home used “dirty electricity,” with a high carbon intensity, versus a home using “clean electricity.” The Emissions & Generation Resource Integrated Database (eGRID) from the US Environmental Protection Agency has data that’s close to what I was looking for. Let’s take a look.
State-by-state carbon intensity
When you scroll to the bottom of the eGRID page, you’ll see a link for eGRID2012 Data File (XLS). That gets you their full data set. It includes data for more things than I was looking for: It’s got SOx and NOx and mercury and all kinds of good data, split up various ways.
What I wanted was carbon intensity of electricity in the 50 states of the U.S. and different regions, and that was in there. They gave it in units of pounds per megawatt-hour and I wanted kilograms per kilowatt-hour, but that was an easy calculation.
Once I had kilograms of CO2 emissions per kWh of electricity produced in a single column, I could see which states were best and which were worst. The first chart (see Image #2, below) shows those data so you can see easily where your state fits in.
Here in Georgia, I’m in the middle of the pack at about 0.5 kg/kWh. The worst states are Wyoming, Kentucky, and West Virginia. Know what they have in common? The best is Vermont, which is so low you can’t even see the column on this chart. Their number is 0.002 kg/kWh.
Problems with the state data
One important fact to note about this chart is that the numbers here are for electricity generated in each state, not the electricity used. To get closer to the latter number, you’d need to include the losses due to transmission and distribution, which aren’t included in the eGRID data. There’s not much in the way of carbon emissions related to the transmission and distribution losses, so the kg CO2 number doesn’t change. But the number of kilowatt-hours decreases, and that has an important effect on all those numbers in the chart. They all get bigger.
The second factor that affects your number is the import and export of electricity among states. My friend Skylar Swinford in Idaho puts it this way:
“I often hear people in Washington and Idaho brag that we have such clean electricity. First I want to say that the social, cultural and ecological impacts/costs of hydroelectricity should not be glossed over. Second, any kWh of hydro wasted by an Idaho or Washington end user will result in that kWh not being exported to another state that then must burn fossil fuels to offset it. We don’t operate on an island, so energy consumption in one state directly impacts the energy mix in all the states located in each interconnect.”
So, the state-by-state chart of carbon intensity gives you a glimpse into the carbon story, but it’s a bit misleading. A better number to use would be the carbon intensity for the regional interconnect that you live in. The second chart (see Image #3, below) shows the eGRID data for the regional interconnects. Unfortunately, they don’t include Canada, so the numbers for the regions that trade with Canada aren’t an accurate representation of carbon intensity.
As you can tell, finding the right data to use for carbon emissions related to the generation of electricity is a bit tricky. If you have other sources of data that show the full picture, please let me know.
Allison Bailes of Decatur, Georgia, is a speaker, writer, building science consultant, and the author of the Energy Vanguard Blog. Check out his in-depth course, Mastering Building Science at Heatspring Learning Institute, and follow him on Twitter at @EnergyVanguard.
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