What are the upstream impacts of internal combustion and electric vehicles?

My previous post comparing the nitrogen oxide emissions of electric and fossil-powered vehicles generated a number of comments (via social media and the blog) to the effect of:

“Power plants may be dirty, but you’re leaving out the upstream impact of refining the fossil fuels to power an ICE vehicle!”

That I did. It was only an analysis of (mostly) local NOx emissions, either from the car’s tailpipe, or the power plant used to generate the electricity (in MInnesota). NOx emissions can have significant local health impacts (inhalation, formation of ozone and smog, etc), but they can also travel long distances. Lifecycle or upstream impacts are also important to consider since we shouldn’t only be concerned about the local air quality impact of our transportation choices.

In an attempt to respond to these comments, I went digging for information on the upstream NOx impacts of the different vehicle fuels discussed in the post (electricity, gasoline and diesel).

The best, most usable, resource I found was the National Energy Technology Laboratory’s Upstream Dashboard Tool (NETL is part of the US Department of Energy). The UDT is “a fast and easy to use tool to determine the environmental profile of various energy feedstocks” according to the documentation. It includes emissions impact information on various “upstream” portions of energy fuels acquisition like raw material acquisition (mining or drilling), raw material transport (the truck, train or pipeline trip fuels must make before they are used) and the “energy conversion facility” (in the case of gas and diesel, this means the refinery process). Basically, you tell it to look at a fuel, and it will give you outputs like air and water emissions, solid waste generation, and water and land use requirements. And it’s all in an easy-to-use excel spreadsheet, just like they advertised!

This tool allowed me to look at the “upstream” impact of the coal and natural gas used in Minnesota’s power plants (to “fuel” an EV), and gasoline and diesel which would be used in ICE vehicles. So now I can answer the question: how do the fuels of ICE and electric vehicles used in Minnesota compare to each other in terms of NOx emissions, accounting for both the “tailpipe” emissions and the upstream emissions?

The upstream emissions

Here are the results from the Dashboard, translated into grams of NOx pollution per mile of vehicle travel:


The Tesla is in fact cleaner in terms of upstream emissions (before the creation of any kWh sent to the electric grid) – responsible for one third as much upstream NOx as either an average gas vehicle or one select diesel vehicle (without a defeat device). This is assuming Minnesota’s electricity mix, which includes 50 percent coal and about 14 percent natural gas. The tesla has no “energy conversion facility” emissions equivalent to a refinery for the liquid fuels, since I’m counting the burning of the coal as part of the downstream emissions.

So, extracting and refining liquid fossil fuels is in fact dirtier (in terms of NOx pollutants) than the extracting and transporting the fuel for an electric vehicle (powered from roughly 75 percent fossil fuels).

The complete picture

Now let’s take a look at the whole picture: from extraction to turning wheels. Here are the results with the downstream emissions included:


Electricity production in Minnesota is responsible for 1.4 pounds of NOx pollution per MWh, meaning an electric vehicle like the Tesla produces 0.21 grams of NOx per mile driven. With Minnesota’s current electricity generation mix, an EV is responsible for emitting about 30 percent more NOx “well to wheels” than typical gasoline vehicle, and 50 percent more than a diesel vehicle.

Electric vehicles can be better for NOx, if we kick coal

NOx rates change significantly based on the amount of coal in the electricity mix. In Oregon, which only gets 6 percent of its electricity from coal (and 32 percent from natural gas), the lifecycle NOx emissions of an EV like the Tesla would be 20 percent lower than an average gasoline vehicle. In Washington, where 75 percent of electricity comes from hyrdopower or other renewables, emissions would be less than half of a gas vehicle. In Wyoming, where 89 percent of electricity generation comes from coal, an EV would emit 80 percent more NOx per mile than a gasoline vehicle on a lifecycle basis. The United States as a whole emits 1.2 lbs of NOx per MWh, translating into a lifecycle per mile emissions rate for an EV that is about 10 percent higher than a gasoline vehicle.

Some Minnesota utilities are on a trajectory to reduce their coal use. However, there is an active political discussion going on right now about the future of coal-fired electricity in Minnesota, and the outcome is uncertain. As I said in the previous post, I think we need to electrify the transport sector to reduce climate risks. However, the choice cannot be between deploying electric vehicles or cleaning up the grid, both must be done simultaneously.


  1. If you’d like to check my math, here is the spreadsheet.
  2. This is still not a full supply-chain analysis, which would account for things like the mining of materials used to build EV batteries and car parts. This is just an analysis of fuels.
  3. Liquid fossil fuels, like gasoline, are getting dirtier over time, measured by carbon impacts, with the addition of new sources like tar sands. The UDT is based on national average compositions for gasoline, so the impact on pollutants like NOx is unclear using this approach. Regardless, electricity still needs to get a lot cleaner.

How many battery-electric vehicles are there in Minnesota?

Inspired by a previous post, I wondered how many battery-electric vehicles (cars that run on just batteries, not hybrids with plugs) there are in Minnesota. This information is not readily available from the DMV. But combining this data and this data from DOE yields an answer as of 2014: 644.

Count of Battery Electric Vehicles in the US by State - 2014

View a larger map.

Is a Tesla cleaner than a dirty diesel?

If you are a Minnesota driver, the answer is yes, but not by much it would not meet federal emissions standards for light duty vehicles. Including energy generation, a Tesla will produce slightly far fewer NOx emissions per mile than a “defeated” VW. But a Tesla in Minnesota is far three times dirtier, in terms of NOx emissions, than the average car on the road, or than federal emissions standards allow for light duty vehicles.

(I was kind of surprised by these results. If you think f I’m missing something here, let me know and I’ll make corrections to calculations and notes, as appropriate.)


Tesla is running this ad, apparently (UPDATE: this may not be an ad, but may have been produced by that twitter user. If you know the source, let me know), and Elon Musk says cars should be tested at random to see if they meet emissions requirements. This is in response to the Volkswagen Scandal.

It’s fairly clear at this point, that in many locations with cleaner electricity sources, EVs have a carbon benefit over ICE vehicles (this EPA calculator gives you results for your area). Minnesota is one of those places, even though our electricity still comes mostly from fossil fuels.

chart (3)

But what about nitrogen oxide (NOx), the pollutant at the heart of the VW Scandal? (Here’s a rundown of the bad stuff NOx does to things that breath air) A VW with a “defeat device” could emit up to 35 times the federal emissions limits for NOx. That could be as high as 2.45 grams or 0.0054 pounds per mile. So how does an EV, like the Tesla, compare?

A Tesla uses 33 kWh for every 100 miles traveled (or 0.33 kWh per mile). According to federal statistics, Minnesota power plants emit 1.4 pounds of NOx pollution for each MWh of electricity generated (Xcel Energy shows a similar 1.5 lbs/MWh in its reporting). That means a Tesla is responsible for 0.210 grams of NOx per mile. So, to fact check the ad: yes, driving a Tesla (in Minnesota) is slightly quite a bit cleaner than a diesel VW with a defeat device.

However, that Minnesota Tesla is responsible for emitting 1.5 times more NOx per mile than the dirtiest cars allowed on the road by federal emissions standards, and 3 times more NOx per mile than the allowable fleet average NOx emissions. So it’s too early for Tesla owners to get smug about their impact on the environment. In fact, they are squarely in dirty-diesel territory. (UPDATE: my math was off in the preceding calculation, it has been corrected). You might interpret that ad another way: Tesla has actually defeated emissions testing – by moving the tailpipe from the car to a distant power plant (UPDATE: again, not sure this is a real ad).

Electric vehicles can be better for NOx – if we kick coal

If you were driving a Tesla in Washington State, which has a NOx emissions rate of 0.3 lbs/MWh, you’d actually be emitting 35 percent less NOx per mile than the average light duty vehicle. Why? Because Washington residents get most of their electricity from emissions-free hydropower.

The break-even point seems to be 0.46 pounds of NOx/MWh, which is about equal to the emissions rate for the state of Oregon. This is what their electricity sources look like:

chart (4)

Oregon only gets 6 percent of its electricity from coal. Minnesota is currently at 50 percent. It’s clear what we need to do to make EVs cleaner: reduce Minnesota’s use of coal for making electricity.

We probably need to electrify transportation to meet the State’s aggressive climate action goals. However, we don’t want to just trade carbon benefits for dirtier air and all the associated impacts (asthma, deaths). We need to simultaneously begin the transition to electric vehicles, AND rapidly decarbonize and de-coal our electricity grid.


  1. Brendan Jordan asserts via twitter that 50 percent of Minnesota EV owners use wind power for their EV charging. This means they either buy, or their utility supplies, wind “credits” to supply the amount of electricity they use for EV charging. If the credit tracking system works, this wind is “additional”, and does in fact reduce emissions. If it’s true (I haven’t seen the data) that’s great, and just another argument for decarbonizing the whole grid. However, this is not the “default” when you plug your vehicle into a charging station at home or at work. Also free wind for EV charging is not offered by Xcel Energy, Minnesota’s largest utility.

Measuring battery charging efficiency

I lied, it’s another solar post, sorry. I think I have another in the works too, but that one will be longer, and have maps!

Usually, I don’t get to see/use the full capacity of the two battery-connected panels on our roof. On perfect sunny days, the battery is usually out of bulk charging (it’s “full”, kind-of) before solar noon is reached, when the panels would be at full output. This is by design, as there needs to be extra capacity in the panels for cloudy days. Here’s what that usually looks like:


By 9 am, the charge controller stops bulk charging, and reduces the amperage going in to the battery. Amps go back up periodically when the deep freeze compressor turns on, but most of the potential production is curtailed, so to speak.

A few days ago, the batteries had dropped to a pretty low state of charge after a few rainy days: slightly under the 50% mark. This is usually lower then I let it go, but won’t hurt unless it’s a regular occurrence. The next day was totally clear and cool – perfect for charging the batteries and trying to track the panels maximum output.


On this particular day, the battery stayed in bulk charging mode until about 1:30 pm. According to the specifications on my panels, under laboratory conditions, the maximum output for each panel should be just over 9 amps (so the output of two should be just over 18). At exactly 12:30 pm, the charge controller was pushing 17.49 amps into the batteries, which was the maximum that day. This is over 96% efficient! That seems like a pretty good result considering potential efficiency losses like the wiring run and the charge controller itself, which takes a percent or two.

So the panels, wiring and charge controller are all performing well (or can, when called upon). I thought this was the case, but hadn’t really tested it fully until now. Of course, getting the energy out the battery is a whole other story (a much more inefficient one). Exploring that will take some different measuring devices, and another post.

Minnesota residential solar installation prices in line with national trends

Depending on how you count, this is my sixth post in a row here about solar. I’ll do my best to discuss something non-solar next time.

CY 2014 was the first year the Minnesota Department of Commerce required electric utilities to report on the total installed cost of distributed generation sources (like solar!) in their annual reporting on DG. Prior to that, they’d just been reporting the amount of resources that were interconnected. LBNL recently put out Tracking the Sun VIII, a report on national cost trends, so I thought I would compare.


I was kind of surprised to find out that in Minnesota, we’re basically right on track with national price trends. It would be nice to look at older data, but it doesn’t exist in the reports.

Nationally, installation prices have fallen an average of over 12 percent each year since 2009. If those kinds of cost declines continue, residential solar could be sub-$2/watt by the early 2020’s. Even in wintry Minnesota, sub-$2/watt rooftop solar (the most expensive kind of solar) begins to look competitive with natural gas and coal on a levelized cost basis.

The next Minnesota DG reports come out on March 1, 2016.

Should more solar panels should face west? (with local data)

Here are two charts I made using data from the output of our grid-tied solar array and data from the Midcontinent Independent System Operator (MISO), the people who keep the regional grid (including Minnesota’s) running.


This shows the total load the grid is using in a given hour and the total production in that same hour from our solar array. Our array faces due south. The shape of MISO’s load curve is fairly consistent from day to day, and so is our production curve (on sunny days). The peaks are not coincident, and solar production drops off dramatically in the peak load time. Data from our home use is even uglier (on weekdays).


The second chart compares the same solar production to price. For this one, I averaged all the locational marginal prices at the Minnesota Hub for all the days in July (average prices can vary somewhat by day and hour). The blue line basically shows how expensive wholesale electricity is in Minnesota at a given hour based on supply and demand (side note: check out this great real-time map of marginal electricity prices in MISO at different locations). Solar production seems to match this curve better in the morning, but still misses the opportunity to offset some of the more costly electricity in the afternoon. In July, west-facing panels could frequently be producing until 8 pm and beyond, when the price peak seems to start dropping off.

Rooftop solar usually doesn’t point west, probably because the incentives and utility rates (at least in Minnesota) are designed to maximize production rather than meeting peak load or reducing electricity prices. The New York Times has covered this dilemma. At current levels of solar generation in Minnesota, the issue of west- vs. south-facing panels doesn’t matter much. As generation grows however, this issue is something for utilities and regulators to consider.

The grid is good

We’ve had an Egauge monitor that tracks our home’s solar production on for about a month now. It’s fabulous. For the last week, it’s also been tracking our whole-home electricity usage. Here’s a graph of hourly average power (in kW) from production and consumption.

weekofsolarconsumptionThe solar installers are still adjusting breakers, so output is down, but here are a few things I’ve learned mostly based on our usage.

  • Our house is never using less than 100 watts. We do a pretty good job with power strips, turning off lights, etc. But even at night, even when the refrigerator is cycled off, we’re using around 100 – 200 watts. There are a few things constantly plugged in (battery chargers, sleeping computers, clocks, etc), and I’ll be tracking them down. I’m curious how close to zero watts we can get during the night.
  • Our weekday usage peaks do not match solar production peaks. In the morning, the coffee pot and the hair dryer are running before the sun rises above the trees. The microwave, dishwasher and washing machine often run in the evening on weekdays. On sunny weekdays, we’re sending a lot more energy to the grid than the house is using (since we’re at work). Weekend usage and production peaks match better (see the last to days on the chart). For many reasons, the grid is good.
  • I’m now more obsessed with finding out how much energy things use, and switching them off. The little red line moving in real time on the screen is a great motivator.
  • Our peak demand is probably about 4 kW. The above graph doesn’t show it, because it’s an hourly average, but we hit about 3.5 kW on a very hot weekend day when a number of window air conditioners were running. This is above our peak solar output, which is probably 2.8 kW under optimal conditions. This is also important for a future post I hope to write exploring what it might cost to actually take our house fully off-grid (at least on the electric side).

Only Wikipedia is accurately tracking solar PV capacity in Minnesota

GreenTech Media recently showed that the main energy statistics agency for the United States, the Energy Information Agency (EIA) was missing information on a whopping 45 percent of installed solar PV. The problem is with their methodology – they don’t count customer-sited solar, like systems on rooftops. GreenTech found that actual solar production was 50 percent higher than official estimates. Three states (CA, AZ, HI) now get more than 5 percent of their electricity from solar, something you wouldn’t know if you only consulted EIA.

Data for Minnesota is even worse. Users of wikipedia will get a far more accurate assessment (which is based on the Interstate Renewable Energy Council’s annual solar market trends report).

EIA data says that Minnesota produced no electricity from solar in 2012, and 2.7 gigawatt hours in 2013. Here is the chart from their Electricity Browser:


In reality, Minnesota produced something like 18.7 gigawatt hours from solar PV in 2013, or 592 percent more than EIA estimates.

I didn’t just use wikipedia data to make this estimate, I used data from the Minnesota Department of Commerce’s Annual Distributed Generation Interconnection Report, which utilities are required to submit each year showing existing and new DG facilities. The number above comes from only six utilities in Minnesota, which I think are some of the largest in terms of number of customers.


Here is the breakdown of installed capacity at the six utilities:


I couldn’t find a report on total installed PV capacity or production on Commerce’s website, but it could be hidden in dockets somewhere.

If you’re looking for accurate data on the growth of distributed generation, like solar, you can’t (yet) count on EIA. GreenTech outlines a bunch of reasons why this is important, including making the EPA’s Clean Power Plan to regulate existing power plants look harder to accomplish than it might be.

In Minnesota, solar is a small (0.04% of total generation in 2014), but growing part of the energy mix. Accurately tracking this growth is important for making good policy, especially in regards to distributed (customer-owned) generation, which is usually outside the control of utility planning processes.

Low-carbon energy, land use and community planning

At Energy Collective, Jesse Jenkins looks at the land use impacts of three low-carbon energy sources: solar, wind and nuclear. On solar:

According to the MIT authors, powering 100 percent of estimated U.S. electricity demand in 2050 with solar energy would require roughly 33,000 square kilometers (sq-km) of land. That’s if we spread solar panels evenly across the entire country. If we concentrate solar production in the sunniest regions, the total land footprint falls to 12,000 sq-km.

Those sound like big numbers. On the one hand they are. Massachusetts (where I reside) spans about 27,000 sq-km, for comparison.

On the other hand, the United States apparently devotes about 10,000 sq-km of land just to golf courses. And as the infographic illustrates, it’s agriculture and forestry that truly drives humanity’s footprint on the natural landscape.

In reality, no one is calling for 100 percent solar energy. Even the most bullish renewable energy advocates typically envision solar providing less than half and usually no more than a quarter of U.S. electricity. (See: “Is There An Upper Limit to Variable Renewables”)

If solar provided one-third of Americans’ electricity, it would require just 4,000-11,000 sq-km.

In other words: with an area no larger than the amount of land currently devoted to golf courses, we could power a third of the country with solar energy.


The above is only assuming greenfield development. And wind:

Powering one-third of the country with wind farms would thus truly impact only on the order of 1,800 sq-km, of which only roughly 600 sq-km would be permanently removed from production.

That’s an almost trivially small amount of land, equal to only 6 percent of the land area wasted, er, devoted to golf in this country.

If well sited and co-located on already disturbed and productive agricultural lands, wind farms could thus fuel a sizeable fraction of America’s energy demand without expanding the human footprint on the land in any meaningful way, except aesthetically.

So, on a national scale, the potential land use impacts of really high proportions of renewable energy doesn’t look like a barrier. But most energy projects will have neighbors, and they may not like the look of solar panels, or the loss of borrowed views.

Additionally, putting solar near the busiest parts of the electrical grid, where it can have the most benefit, may conflict with local communities’ plans for future development. A solar farm will probably pay far less in property taxes than residential, commercial or industrial development.

Both of these local conflicts may mean that a significant portion of future solar needs to be co-located with buildings (on the roof), parking lots and other developed areas to minimize land use conflicts and/or reduce transmission costs.

Wind and solar now provide 10% of growth in China’s energy consumption

I got into a twitter discussion about a blog post that was challenging the idea that China is seeming a “renewables revolution”. I do not claim to be a China expert, and I hope I do not qualify as an insta-expert/pundit. However, I can read a spreadsheet.

The blog post compared the growth in solar and wind in 2014 to the average growth in total primary energy consumption averaged over the last decade. I argued that one data point was not a good way to judge a “revolution”, much less discern a trend.

Trying to be proactive, rather than argumentative, I produced the data I thought should be in the post from the same data source.


This chart shows the percentage of the growth in China’s primary energy consumption that is being met by new wind and solar sources (according to BP’s Statistical Review of World Energy 2015)

Before 2005, effectively none of the growth in energy use in China was being met by new wind and solar generation. In 2013, about 12 percent of the growth was provided by new wind and solar resources. In 2014, that figure was about 11.5 percent. So the share of China’s growing energy consumption that is provided by new wind and solar is definitely increasing, and hence so is total wind and solar production as a share of total consumption (1.4 percent in 2014 according to BP).

Here’s another way to look at it: in 2000, wind and solar production in China was basically zero. In 2014, production from wind and solar sources in China was more than the total annual energy consumption of twenty six countries listed in BP’s data book (including developed countries like Kuwait, Austria, Switzerland, New Zealand and Denmark). So the solar and wind generators in China can now provide the equivalent of all the energy (including equivalent of fuels for transportation and heating, not just electricity) required to power a small, modern western European country.

Is this a “revolution”? I’ll leave that to others. I’d say the growth of solar and wind production in China is very, very strong. Of course, the growth in total energy consumption in China is very, very strong also.