by Dr. Donald R. van der Vaart
Former Secretary, North Carolina Department of Environmental Quality
Governor Cooper’s Executive Order 80 claims to seek reductions in greenhouse gas (GHG) emissions to combat global warming. A major component of the order is the promotion of electric vehicles in North Carolina. Ironically, promoting electric vehicles will increase electricity use and actually exacerbate global warming to the extent GHGs are the cause. Instead, Governor Cooper should focus on reducing the carbon intensity of our electricity grid by pushing for nuclear power.
Electric vehicles are not more fuel-efficient than similarly sized gasoline-powered vehicles. Well over 10 years ago, the United States Environmental Protection Agency (EPA) developed an “equivalent fuel mileage” for electric vehicles, denoted as MPGe. The metric was widely misinterpreted as being useful for comparing electric vehicle fuel efficiency with the fuel efficiency of internal combustion engine vehicles. (See “Decoding Electric Car MPG” for further discussion.)
Unfortunately, MPGe only describes the efficiency of the electric vehicles in converting the energy stored in the battery to mechanical energy, i.e., turning the wheels. Values of well over 100 MPGe are reported making electric vehicles appear to be very fuel-efficient because it ignores the energy required to charge the battery. It should not be used to compare electric vehicles with internal combustion engine vehicles.
Such outlandish fuel efficiency numbers should actually jar intuition. How could it be that a gasoline vehicle that burns fuel onboard by converting that chemical energy directly to mechanical energy is only one-third as efficient as an electric vehicle that relies on the combustion that has been transmitted over miles of wires and then used to charge a battery in our garage?
Apparently, the U.S. Department of Energy didn’t agree with EPA either. The department published an alternative method on June 12, 2000. Although competing methods and assumptions exist, the Department of Energy calculated fuel efficiencies for electric vehicles that are roughly one-third of those using EPA’s misleading method.
To illustrate the importance of including the fuel needed to charge the batteries, an example calculation based on a 2019 Honda Clarity electric vehicle using the Department of Energy method is helpful. The EPA (battery to wheel) fuel efficiency is given as 114 MPGe. Using DOE’s approach (generation station to wheels) to take into account the losses associated with electricity generation, transmission, charging, etc., the efficiency is calculated to be 34.5 miles per gallon. This represents the car’s efficiency assuming the electricity was generated by gasoline. This can be better compared with the fuel efficiency for the gasoline version of the Honda Civic of approximately 36 miles per gallon, although losses associated with the transportation of the vehicles to retail outlets would reduce this number.
Proponents of electric vehicles point out that, regardless of their efficiency, electric vehicles are still better to combat global warming than gasoline vehicles so long as the electricity comes from low-GHG emitting sources. To the extent that GHG emissions are linked to global warming, this is absolutely true. The Honda Clarity discussed above had a calculated fuel efficiency of roughly 34.5 miles per gallon, assuming gasoline as the fuel. Using the carbon dioxide (CO2) emissions associated with the combustion of different fuels as a basis, if coal were used as the exclusive fuel to generate the needed electricity, the fuel efficiency would drop to 25.8 miles per gallon. This represents the effective fuel economy that would emit the same amount of CO2. Similarly, assuming natural gas as the basis, the effective fuel economy would rise to 46.4 miles per gallon. The reality in most markets in the United States lies somewhere in between.
Recognizing that the current carbon intensity of our electricity grid is not zero and that electricity usage would increase by approximately 30 percent by transitioning to all-electric vehicles, the question then becomes whether we should focus on cleaning up the grid before we actually increase the use of electricity. In fact, the picture is bleaker than this. Current trends in U.S. electricity production is that natural gas use is rapidly increasing and that nuclear energy is threatened. Both of these trends would argue against electric vehicles right now. Here is why.
First, recent research shows that electricity generated from natural gas combustion is as bad or worse for global warming than coal. These researchers argue that methane, the major component in natural gas, is a far more potent GHG than CO2. They then argue that the production and transportation of natural gas lead to significant leaks of methane. When the increased potency of methane is considered, these leaks actually lead to higher overall GHG emissions than coal plants. Increasing the use of natural gas for electricity generation could actually increase GHG emissions according to these researchers.
Second, current policies on renewable power could lead to a reduction in nuclear power. Under current policies and regulations in North Carolina, Duke must buy solar power whenever it is produced. As more solar power is produced during the daylight hours, Duke must reduce generation from its other plants. Duke says it eventually may need to reduce power from its nuclear plants to accommodate increasing solar generation. It turns out that when zero-emission nuclear plants are dialed back to make room for solar, greenhouse gas-emitting gas plants must be employed to give nuclear plants time to ramp back up when the sun goes down. This is a step backward.
Additionally, while aging nuclear plants generate some of the cheapest electricity in the country, they are under attack. Citing economic competition from natural gas and heavily subsidized renewable energy, the closure of more than five nuclear plants have been announced since 2013. These plants will be replaced by natural gas with or without some renewable sources as well. In North Carolina, the closure of a single nuclear plant will erase all of the GHG reductions gained by becoming the nation’s second-biggest solar power producer.
In sum, the current grid is not becoming less carbon-intensive. Instances of GHG reversal have been reported in other markets, most notably Germany. Under such a trend, the addition of electric vehicles to the nation’s fleet would increase electricity usage and be counterproductive.
North Carolina should not promote the electrification of our transportation system until after the carbon intensity of our grid has been reduced. In the meantime, the science of the impact of natural gas on global warming should continue to be studied.