Finally. If you don’t like being dependent on oil—but find that you do need to drive—you’ve got at least one decent option. The Nissan Leaf is the first mass-produced, mass-market electric vehicle to hit the US sales floors in…well, essentially forever. (Yeah, I know about the Tesla and the EV1. But the former is too expensive to be in range of most families, and the latter was never really offered for sale—you could only lease it.)
The Leaf’s a bit pricey, but for many families there are federal tax breaks that can help. And while the car has hit a few bumps in the road—including a recent recall to reprogram the starter, and some complaints about shorter than expected range—the car’s overall reviews have been pretty positive.
But if your main concern is the climate impact of your driving habits, how does the Leaf fare? The EPA label says that the car gets the energy equivalent of 99 miles per gallon—106 mpg in the city, 92 mpg on the highway. Pretty good, in other words!
But the EPA also says that the car emits “0” pounds of climate-warming emissions each year. And while this is technically true, it’s also misleading. No, the Leaf doesn’t have a tailpipe spewing carbon-laden exhaust. But the electricity the car runs on doesn’t magically appear out of nowhere. And even in the Northwest, blessed as we are with lots of hydropower, some of the electricity that comes out of our sockets started out as coal or natural gas. So despite what the EPA label suggests, the Leaf does have some climate impact.
How much? Let’s run some numbers to see…
There are probably as many ways of calculating carbon footprints are there eggheads. So I’ll do my best to explain my estimates, without making things too terribly complicated.
The Northwest Power and Conservation Council says that generating the average kilowatt-hour of electricity (enough to power 10 100-watt bulbs for one hour) in the Northwest produces a little over a half pound of CO2. (See the chart on page 8 of this pdf.)
But there’s a difference between the average carbon emissions and marginal carbon emissions. The marginal emissions represent what power source gets turned up or down when electricity demand goes up or down just a little bit. The NWPCC estimates that in the Northwest, emissions from marginal electricity average about 0.72 pounds per kilowatt-hour. That’s higher than the region’s average emissions, because natural gas generation tends to be “on the margin” (see page 11 of the same pdf).
Of course, not all of the power that gets produced at a generating plant even makes it to your home. Some is dissipated as heat during long-distance transmission, or as it’s distributed from the substation to your home. Based on the latest data from the Energy Information Administration (from this page, access the “Table 10” spreadsheet for each Northwest state), transmission and distribution losses in the Northwest total about 6 percent.
I thought it would be worthwhile to compare the Leaf with a few examples of gasoline-powered cars. I’ve estimated in the past that the lifecycle emissions from gasoline total 25.77 pounds of CO2 equivalents per gallon, including both CO2 from the vehicle tailpipe as well as the “upstream” and trace emissions from fuel extraction, refining, distribution, and combustion.
So based on all this, how do the Leaf’s emissions stack up? Take a look:
As you can see, the Leaf’s greenhouse gas performance depends crucially on where its electricity comes from.
Personally, I think that the “right” way to think about the Leaf in the Northwest is the bar in the green: the marginal carbon emissions. And on that measure, the Leaf is a lower-carbon vehicle than the Prius. In fact—and purely coincidentally—the Leaf’s emissions work out to be just about the same as its EPA rating: the equivalent of a gas-powered car that gets about 99 miles per gallon.
But on the other hand, if the electricity that powers the Leaf comes from a coal-fired power plant, then the battery-powered car performs far worse than a Prius. In fact, by these calculations, it’s the equivalent of a car that gets about 30 mpg: better than the average car, but certainly not much to brag about.
I take two things away from all this. First, electric cars in the Northwest appear to be a pretty good deal for the climate. But second—and more importantly—coal-fired power negates all of the climate benefits of electric cars. If power companies in the US West were to build lots of coal plants in order to power a fleet of electric vehicles, electric car buyers will be doing the climate no favors. People might as well buy a small-and-efficient car that burns plain old gasoline.
So if you really want to drive green, you ought to focus on getting rid of coal, as fast as possible. What car you drive is important; but where your electricity comes from can make an even bigger impact on the climate.
Leaf photo courtesy of Flickr user Rutger Middendorp, distributed under a Creative Commons license.
And a technical note: the NWPCC’s estimates of emissions for gas turbines and coal plants may be a bit low, since they may not include all upstream emissions. That said, their estimates are roughly in line with other life cycle estimates for emissions from electricity generation. Life cycle analysis for natural gas power seems to have particularly wide variation—so take these figures as reasonable estimates, not the gospel truth.
Ron
Clark,You make valid points about the source of electricity but I think you left an important benefit of electric cars out of the mix. Namely, storage. Storing electricity in the batteries of millions of electric cars has huge potential to help smooth out ramps that our utilities contend with and make some peaker (usually thermal) unnecessary. We need storage for renewables to be truly impactful.Best,Ron
JKD
Just like the electricity doesn’t come out of nowhere, the gasoline doesn’t magically appear at the gas station either… Unless you include all the energy used at the refinaries to produce the gallon of gas (there’s a reason each refinery has its own power plant) and CO2 used in gasoline distribution then your analysis is no better than saying that electrics contribute zero emissions.
Ethan Seltzer
Once again, the only real way to drive green is…not to drive. Looking to the Leaf, Prius, or anything else as a way to be green and not change trip making behavior doesn’t wash. Further, every Leaf purchase creates, in all likelihood, the contribution of a current carbon burner to the fleet. That is, trading the Volvo or the Prius for a Leaf doesn’t remove a car from the road. In the end, making really green choices is harder than deciding what car to buy.
Matt the Engineer
Ron,I’ve heard a lot of claims about using electric car batteries to level off peaks, but I just don’t get it. It seems to me the cost of an electric car is all in the batteries, and batteries only have so many cycles until they’re big toxic paperweights. So wouldn’t electricity have to be amazingly expensive to justify using something as expensive as electric car batteries to run your toaster?
VeloBusDriver
We are receiving less oil from traditional oil fields in Alaska and more from the far more CO2 intensive Athabasca tar sands in Canada. This means there is really a “marginal” CO2 emission number for gasoline refined from Tar Sands oil although I’m not certain what it is. “Marginal NW” power can mean many things, depending on the time of day, weather, snow pack, etc. However, many electric cars will likely be charged at night when the power comes from base load sources. I’d suggest looking at the best case (hopefully) of night-time charging. I believe both the Leaf and the upcoming Ford Focus Electric will have the capability to set times for recharging.
curtegg
I dispute your statistics. If you account for extraction, transportation of the fuel, refining, and vapor loss required for gasoline, then even off coal-fired power grid the CO2 emissions are less for EVs. England did a complete study on this and found that EVs are about 1/3 less than even the most efficient TDI diesel car (that beats the prius in mileage).
JKD
If Matt is the engineer he claims to be then he should know that batteries do not become toxic paperweights – they get recycled. Also, I don’t mind replacing individual modules 8 years from now when LEAF’s warranty runs out. Even if you don’t you still have 50% capacity avaiable which is still plenty for most people’s daily needs (and that’s EIGHT years from now…)
Eric de Place
Curtegg & JKD,Clark’s statistics are accurate, and he DOES account for all the “upstream” emissions of gasoline. To wit, he writes: “I’ve estimated in the past that the lifecycle emissions from gasoline total 25.77 pounds of CO2 equivalents per gallon, including both CO2 from the vehicle tailpipe as well as the “upstream” and trace emissions from fuel extraction, refining, distribution, and combustion.”For reference, a gallon of gasoline produces roughly 19.6 pounds of CO2 when combusted. That figure goes up by 5 or 6 pounds when you factor in all upstream stuff. That’s why he attributes 25.77 pounds of C02 per gallon.In other words, the comparison is, in fact, as close to an apples-to-apples comparison as possible.
Tom Sanford
I have solar PV panels on my home, 12 panels rated at about 200 watts each or a 2.4 KWH system. My question is how close would that come to charging an EV on a sunny day? It seems the only true way to make an EV have no emissions is to produce the fuel by yourself on your own site, no transmission. Though probably the only real way to radically reduce the CO2 is to ride my bike rather than use the car at all! I still need to provide transportaion for folks who have mobility challenges.
Clark Williams-Derry
Ethan- Amen to that. Curtegg & JKD – I did my best to account for upstream & trace emissions from gasoline, including vapor loss. If you’ve got a different set of numbers, I’d love to see them! I haven’t seen a single, definitive source, so I had to roll my own. That said, I DIDN’T look at upstream and trace emissions from coal or gas. I felt comfortable with the NWPCC coal & gas figures, since they actually came out at about the same place as other life-cycle studies for coal & gas-fired power. And Curtegg—this looks specifically at the real-world efficiency of an actual EV, not EVs in general. I’d love to see the English study, but I don’t think that general conclusions about EVs in general are necessarily relevant to the actual, real-world Leaf.Velobusdriver – Agreed that tar-sands oil is dirtier, but I actually don’t know how that affects the “marginal” emissions from the global petroleum system. In the short term, Athabasca will keep producing—they have to pay their debt. In today’s oil economy, it may be the cheaper, more easily dispatchable oil that’s “on the margin”. But over the long term—I just don’t know. You may well be right that dirtier oil is on the margin over the long haul. It’s not clear to me whether marginal electricity has similar issues—is it the harder-to-access coal, more energy-intensive gas from fracking that’s on the margin? How do trace emissions from fracking factor in? And over time, how will those trends interact with renewables & storage? Complicated! Oddly enough, the 2010 nightime marginal CO2 emissions for the Northwest grid, as modeled by NWPCC, were a bit HIGHER than the all-day average, which was what I used. See figure 3 of their report. That struck me as odd, but here’s exactly what they say: “Gas-fired power plants with relatively high variable costs are typically on the margin during heavier load hours, whereas coal-fired plants with lower variable costs can be on the margin during nighttime and weekend light load hours. Therefore, both the physical quantity, and dollar value, of avoided CO2 emissions vary with time.” Weird, and not what I expected, but I have no standing or expertise to dispute them.
Matt the Engineer
[JKD] Batteries lose capacity with number of cycles. That 8 years assumes a cycle or two a day. Double that, and your batteries only last 4 years. How many thousands of dollars did that just cost you? Even if you wiped out your entire power bill it wouldn’t pay for half your batteries.
Chris Jones
I’d love to see this comparison extended to:- Wind power in the Northwest, assuming that I pay for 100% green power through my utility (I know, I don’t actually get the electrons from the wind turbines, but still, there’s a point to be made).- Biodiesel from Sequential Pacific, which is made mostly from used cooking oil, in my 50-mpg Golf TDI. It should have a better profile than the Prius, certainly, and maybe the Leaf.- A bicycle.
Eletruk
First off, Puget Sound Energy (and many if not most utilities) offer an option to subscribe to renewable energy, so you can in effect have truely zero emissions.Second – @ Matt “the engineer” Lithium batteries (as in the Leaf) are not toxic, they are recognized by EPA as land fill safe, but to throw them away would be stupid, better to recycle them. And yes, batteries may have “only so many cycles” but those cycles are basically good for as many miles as your typical infernal combustion engine (which also become big paperweights after so many cycles). The battery packs are warranted for 100K miles, but that doesn’t mean they stop working at 100K miles. Do the math, the cost of the car + maintenance + fuel to power it is cheaper for the Leaf than for a comparable ICE vehicle over the life of the vehicle.@Tom, depends on how many miles a day you drive. The Leaf uses about 240WH/mile so the solar array would charge a bit less than 10 miles per hour (accounting for conversion losses).
Earl
The conclusions that EVs are bad under certain circumstances is not really helping anything except to make a few smug Prius drivers feel they’re still the greenest thing on the road. If we drive EVs, the worst you can really say is then your CO2 emissions are generally as good or better than an ICE and will only get better as we clean up our electrical grid.Just because there is one possible exception of electricity purely from coal doesn’t mean EVs aren’t the best solution to the evils of petroleum that we have today.
Matt the Engineer
[Ele], you just repeated [JKD]’s argument while missing my point. Those 100k mile batteries will only drive you 50k miles if you cycle them once a day while parked in your garage. You’re losing half the value of you batteries.And I’m happy to amend my characterization to “recyclable, possibly toxic paperweights.”
Paul Scott
3 points…(1) Most people waste more electricity in their homes than they’d use in an EV. If you have concerns over the pollution from coal or NG generated kWh, then be very efficient in your use of electricity at home and you’ll find that you can reduce your use enough to cover most, if not all, of you driving needs. A reasonably efficient LEAF driver can easily get 4 miles/kWh. I get 4.5 – 4.8 miles/kWh on my LEAF.(2) Even if the environmental benefits were even with a Prius, we’re still better off going electric because of the national security issues surrounding the use of a fuel that is derived primarily from the unstable middle east. The U.S. military spends $75-$80 billion of our tax dollars every year protecting access to the world’s oil. This is in addition to the $1.5 TRILLION dollars we’ve spent on the Iraq and Afghanistan wars. Not to be left out are the thousands of dead soldiers and tens of thousands of wounded. A few hundred thousand dead civilians is nothing to sniff at either.We’ve never had a war over electricity, and we never will.(3) Our economy is reeling from buying foreign oil. A full 45% of our trade deficit comes from this expense, over a billion dollars per day leaves our economy. Even worse, when you buy gas, over 90% of your money leaves your local economy, never to return. Here in CA, we lose over $50 billion each year from our state’s economy. That’s a huge drain and it’s killing us. In OR and WA, can you afford to lose billions from your economies? When you buy an EV, 100% of your money stays local. You’ll give your utility about 15-20% of what you were giving the oil companies, the rest stays in your pocket. Your utility is local, or regional at worst. You’ll spend your money on local goods and services, creating jobs and wealth in your community as you do so.It’s good to look at the enviro aspects of driving, but the national security and economic arguments for EVs are just as strong.
Barry
One benefit of electric cars that is usually overlooked is that they CAN be cleaner if you put clean energy into them. Gasoline cars like Prius (which I own) can not do this.I think the hardest challenge for humanity in dealing with climate destabilization is the replacement of the literally billions of pieces of fossil fuel REQUIRING infrastructure…like cars. This will prove a bigger task than cleaning the electricity sources.If you are going to buy a car, buying an electric car instead of a fossil fuel requiring car is essential. We will never stabilize the climate as long as people keep sinking so much of their capital into new fossil fuel burners that last many decades.Plus buying electric cars instead helps increase deployment which is essential to driving down costs. The Germans’ have led the world in paying for deployment of solar which has rapidly driven down prices of solar—a key step. USA could do the same with electric transport.
Richard Diamond
I would like to note in Texas when our selecting electric power provider, we have the choice to select 100% renewable power ($.087 per kwh). I would also note that coal, as nasty as it is, is sourced domestically, while oil is imported from governments hostile to US interests. Better yet, EV cars give you a choice – an internal combustion engine does not. Another benefit – I have a Leaf – is that I haven’t been to a gas station since taking delivery
VeloBusDriver
Richard, you may not have been to a gas station but at some point in the future, assuming you hold onto the car for the long-term, you will likely need to purchase a new battery. It will be interesting to see how long these new batteries last, or more accurately – how long they provide a useful range, and how much they cost to replace. I have been unable to get a salesman to quote me a cost on replacement. Since I like to drive my cars into the ground, this is a legitimate question that they should be able to answer.The New York Times has an article digging into the question. An interesting possibility: When car batteries no longer provide enough range for drivers, electric utilities are interested in purchasing the old batteries for providing peak power storage.Don’t take this as an indictment against electric cars though. I’m just waiting for a Ford Focus Electric or possibly a Leaf made in the USA. 🙂
rafael
Hmmm this seems to be written by someone somehow related to Oil companies… lol
Leo Z.
The blogger has a really bad sense of logic.
Even though his finding is true (which is not), his conclusion is just too weird:
“You should get rid of coal”? How can anyone do that?
A better proposition is to ask businesses to buy renewable energy or install solar PVs to power their EV fleet, just I and many others have done at home. It’s cheap and totally green.
Back to his comparison between gasoline and coal. You can’t just talk about CO2. You have to include human cost as part of the equation. Too many young kids have been killed or disabled in this country and countless more in the middle east just to get the oil into people’s gas tanks. When you see disabled 18 year old veterans, how can you still say gas car is a better option than EV?
When you drive a Prius or any other gas-powered vehicles, they are not just burning oil, they are also running on blood!
Conclusion:
The blogger is either stupid, or that he just tries to make a sensational statement so that he gets clicks to get paid.
Eric de Place
Fortunately, the coal used to generate electricity for EVs does not kill or disable miners, does not send massive amounts of toxic pollution into local communities (as well as halfway around the world), and does not leave behind a trail of irreparable ecological harm. Just so, there are no environmental consequences to obtaining natural gas for electricity to power EVs.
Leo Z.
Your logic goes like since coal is no good (which I agree) then we have to stick with oil (which I don’t agree). It’s the same logic as in the blog: since US northeast uses coal for electric power mostly, people should use gas cars rather than EVs.
This logic is entirely wrong. It should go like this: since both oil and coal are bad, people should go with EV and use solar or wind to power it.
Just look at Germany. They are further north even compared with US Northeast, but their solar is expected to cover 25% of all power production by 2050. In the US we don’t even need to build solar in the north. Just invest in solar projects in the south and the grid will transmit power to wherever.
With EVs, renewable energies make even more sense. So for people trying to build a green fleet, look no further than EVs, and use the opportunity to switch to solar and/or wind!
Leo Z.
Exactly! Just like oil rigs do never explode, killing rig workers and ruining the oceanic Eco-system forever; or like oil pipelines do never leak; or like oil tankers do never sink; or like refineries do never explode either.
Please give me a break! I’m talking about solar. Why do you make it sound like I’m a coal guy? Please read the full comment before replying.
I use solar to power my house and my Leaf. Never been happier in my life living a guilt-free lifestyle.