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Batteries

Electric vehicle critics will often tell you that the environmental cost of the batteries is the “dirty little secret” that nobody is telling you about. The claim is that the manufacturing impact of the batteries is so high that we might as well just keep burning gasoline. The origin of this statement is an early and flawed study from 2017.

Let’s examine their claim in more detail.

Battery trends

Battery technology is advancing rapidly. You can see this in the price curve. In December of last year, Bloomberg NEF reported the first instances of vehicle batteries priced at below $100/kWh. At $100, most analyses show EVs priced equivalently to internal combustion engines. For comparison, a decade early that price was $1100/kWh. That means that 10 years ago, the price of the 53 kWh battery in Tesla’s original roadster was over $50,000. It’s no wonder those early Roadsters were so expensive!

The environmental cost of manufacturing vehicle batteries is also falling. A recent study estimated the manufacturing impact of current battery technology at 75 kg CO2e/kWh of battery capacity, down from 89 kg in 2019.

Analysis

The assertion made by the EV industry is that the increased environmental impact of manufacturing the vehicle is offset by the decreased impact of using the vehicle. Is that true?

To figure out the answer to that question, we need to know the CO2e impact of running a conventional vehicle vs an EV. Then, let’s add in the CO2e impact of the battery pack, divided over the expected lifetime of the battery, and we should have our answer.

For the sake of simplicity, let’s assume that the manufacturing impact of a conventional vehicle and an EV is roughly the same, excepting that the EV has the added impact of the battery pack. It’s not entirely true, because the conventional vehicle has a higher carbon cost to build than the EV (without the battery), but for the sake of simplification, let’s assume that they are the same.

My previous vehicle, a 2015 Ford Fusion, averaged about 23 mpg in actual usage. Ford rated it for 28 mpg, but I tracked my gasoline purchases over the lifetime of the vehicle, and it was roughly 23 mpg. I may have a bit of a lead foot. Gasoline combustion produces an estimated 18.95 lbs of CO2e per gallon used. Annually, I drive around 10,000 miles, which means that car was producing 8,226 lbs of CO2e annually.

My new vehicle, the Tesla Model Y AWD, is rated by the EPA for 28 kWh / 100 miles of driving. The Tesla should use about 2,800 kWh of electricity to drive the 10,000 miles I drive in a year. Now all we need to know is the CO2e costs to generate the electricity. According to the EPA, in the United States, the electricity industry as a whole produced an average of 0.92 lbs of CO2e per kWh of electricity generated. So, assuming that my power utility emits the same CO2e as the EPA average electrical utility, my CO2e costs will be 2,576 lbs. More on that in a minute…

FordTesla
Miles Driven10,00010,000
Electricity Used0 kWh2,800 kWh
Fuel Used435 gal0 gal
Unit Emissions18.95 lbs / gal0.92 lbs / kWh
CO2e Emitted8,226 lbs2,576 lbs
Annual operating emissions comparison

So for me, my old Ford emitted 5,650 lbs more CO2e annually than my new Tesla does.

Now let’s get back to that battery pack. Recall that the manufacturing CO2e impact of a battery is about 75 kg CO2e / kWh of capacity. So manufacturing the Tesla’s 75 kWh battery will emit about 5,625 kg of CO2e, which converted to lbs is 12,375 lbs. And then we have a simple calculation.

Years to "break even" = Battery Manufacturing CO2e / Annual CO2e savings.  

So, for me, it will take about 2.2 years before the manufacturing impact of the battery is recovered completely.

My Utility is PSE

I buy my energy from Puget Sound Energy here in the King County, WA area. PSE’s generation mix is roughly 1/3 renewable, 1/3 coal, and 1/3 gas.

SourceEmissions
Coal2.2 lbs / kWh
Natural Gas1.0 lbs / kWh
Renewable0 lbs / kWh
Blend1.06 lbs / kWh

Compared to the national average, PSE is actually a pretty dirty utility. My Tesla driving will generate 2,968 lbs of CO2e annually. And my emissions “payback” will extend to 2.35 years. What a calamity!

Fortunately, PSE has a green energy option, which we have chosen for our household. For an extra $.01/kWh (about $15/mo) we buy an energy mix which is generated 95% from solar and wind, and 5% from biogas. Biogas has about the same emissions profile as NG, which means that the PSE clean energy option produces about 0.05 lbs CO2e / kWh. Some folks consider biogas neutral environmentally, but let’s leave that for another day. In any case, my new Tesla’s CO2e footprint using PSE green energy is now reduced to just 140 lbs CO2e annually, and the “pay back” time for the battery is now just 1.5 years.

Over the 5 years I owned the Fusion, I estimate my emissions at about 41,000 lbs CO2e. I expect the Tesla to be a third of that. Automobiles have a lifetime of about 200,000 miles. Over 200,000 miles the Ford will emit 165,000 lbs CO2e. And if I own the Tesla that long? 15,000.

Your numbers will vary, but the calculation is not hard to do. And no matter how you do the numbers, there simply is no case that the environmental impact of EV battery manufacture outweighs the benefit of not burning gasoline to run a vehicle.

Case closed.

By Alec

Nerd, entrepreneur, adventurer, father, and enthusiastic amateur photographer, blogger, baker and cook. Aspiring yogi. Lifelong learner. Lives in the beautiful Pacific Northwest of the USA with Joanne, and the demanding feline Mr. Lucky Stripes.

Obligatory lawyer words: I'm just a climate nerd with an opinion. Although I work for Microsoft, please don't confuse my personal statements here with the company's official position.

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