Electric Vehicles, Part 1

I asked on Instagram about what questions you have on electric vehicles. Here are my answers!

“Doesn’t owning an electric car cause greater damage than a gas car because of the energy generation?”

This is actually a surprisingly complex question to answer.

Electric vehicles (EVs) get their energy from electricity, which is regional. Combustion engine vehicles get their energy from gas which has a similar impact regardless of where you live in the US. In a region with a majority of the electricity coming from coal, an electric vehicle is probably worse than a fuel efficient car (in terms of carbon emissions), especially when comparing an electric vehicle to a hybrid (Yuksel 2016 [1]).  The image below from Yuksel 2016 has hybrids in the columns and battery electric vehicles in the rows. What it shows is that in 2013, the Toyota Prius hybrid was less carbon emitting than the Chevrolet Volt; whereas the plug-in Prius was less emitting than the Mazda hybrid. For the Prius hybrid vs. Prius plug-in electric vehicle, it depended where you lived. In 2010 an electric vehicle was better than a gasoline combusting car in California, but worse in North Dakota [1].

Image source: Yuksel 2016 [1], Comparison of carbon emissions between battery electric vehicles and hybrids. It’s important to note that this is a comparison with hybrids, not your gas guzzling SUV or even your grandma’s old car.

Differences across the map are a reflection of California having a cleaner grid (more renewables, less coal) than places in the upper Midwest. The grid has gotten much ‘cleaner’ in the past decade (Holland 2020 [2]) primarily because of coal getting decommissioned and natural gas plants (and wind & solar) getting built. Today, in most places around the country, the grid is clean enough that a plug-in electric vehicle is less emitting than a combustion engine vehicle (although good hybrids can be just as clean as electric vehicles in some places!)

Image Source: Holland 2020 [2], Emissions from electricity has really come down in the US in the last decade. This makes having an EV less-emitting today than it was in 2010.

Marginal vs. Average electricity consumption:

Let’s say that there is 100 MW of electricity demand in your area. Adding an electric vehicle to your house’s electricity demand increases the demand to say, 100.1 MW in your area in the evening. This extra marginal demand isn’t enough to build a whole new power plant, instead it is just enough to make the local utility add their ‘peaker plants’ to the grid, the power plants that are small, inefficient, and only go on when they have a tiny bit of extra demand. Graff Ziffin 2014  argues that these dirty coal plants should be what count towards your EV emissions, because it is the plant that actually gets turned on to meet your EV’s demand [3]. The case is always true that the last bit of power used comes from the most expensive electricity than the first bit of power. Renewables cost almost nothing to operate, so once they’re built they are going to always be ‘on’, but demand changes throughout the day, so it’s the coal and natural gas plants that go on in the evening and late at night to meet the last bit of electricity demand (the margin).

Image Source: PJM Learn [4] “How PJM Schedules Generation to Meet Demand”

My personal push-back to the ‘marginal emissions’ argument is that electric vehicles are getting adopted at non-marginal numbers; instead of causing a marginal increase (increasing the red in the curve above), they could cause their region to need new electricity generation (raising the whole curve, so increasing the green and blue), especially as people charge more evenly throughout the day, like at work or while they grocery shop. When new power plants get built they tend to be cleaner than the one’s getting shut down, so new EVs can drive new generation expansion (pun intended, sorry).

Last thought on the ‘greenness’ of EVs: combustion engine cars will always have high emissions. EV’s have emissions reflective of the grid, so an EV’s emissions in three years may be less than its emissions today if the grid gets cleaner. The transportation sector is the largest source of greenhouse gases in the US, so we just won’t make our climate goals by continuing to drive gasoline cars. We need the grid to ‘clean up’ for EVs to be truly low emission, but there’s no scenario where a gasoline car can be low emission.

Ask me a question about electric vehicles!

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References:

[1] Yuksel, T., Tamayao, M.A.M., Hendrickson, C., Azevedo, I.M.L., Michalek, J.J., 2016. Effect of regional grid mix, driving patterns and climate on the comparative carbon footprint of gasoline and plug-in electric vehicles in the United States. Environ. Res. Lett. 11. https://doi.org/10.1088/1748-9326/11/4/044007

[2] Holland, S.P., Mansur, E.T., Muller, N.Z., Yates, A.J., 2020. Decompositions and Policy Consequences of an Extraordinary Decline in Air Pollution from Electricity Generation. Am. Econ. J. Econ. Policy. https://doi.org/10.1257/pol.20190390

[3] Graff Zivin, J.S., Kotchen, M.J., Mansur, E.T., 2014. Spatial and temporal heterogeneity of marginal emissions: Implications for electric cars and other electricity-shifting policies. J. Econ. Behav. Organ. https://doi.org/10.1016/j.jebo.2014.03.010

[4] PJM, “How PJM schedules generation to meet demand”, https://learn.pjm.com/three-priorities/keeping-the-lights-on/how-pjm-schedules-generation-to-meet-demand