EPA Sets CO2 Accounting for Plug-in Electric Vehicles for Model Years 2012 to 2016

Today, EPA released the final rules for the historic new CO2 tailpipe standards for cars and light trucks.  In the rule, the agency describes how it will account for emissions for plug-in electric vehicles that occur not at the tailpipe but at the power plant. Let’s take a quick walk through the approach, which applies only to vehicles produced in model years 2012 to 2016.

EPA is retaining their proposal to count vehicle emissions as zero grams per mile for plug-in electric vehicles when operating on grid electricity but the agency is limiting this scoring to the first 200,000 vehicles produced by each manufacturer.  Zero g/mi scoring will also be applied to fuel cell electric vehicles that get their energy from hydrogen. The zero-emission scoring is intended to incentivize automakers to produce full electric vehicles (EV), plug-in hybrid electric vehicles (PHEVs) and fuel cell vehicles (FCVs) and the cap applies to each manufacturer’s cumulative MY2012-2016 EV+PHEV+FCV production. EPA is also providing an additional sweetener for manufacturers that act early. For automakers that produce 25,000 advanced technology vehicles in MY2012, EPA will expand their manufacturer production cap to 300,000. The zero emissions scoring, however, applies only to when the vehicle is operating on grid electricity—that’s all miles for EVs, but less than 100% for PHEVs—or hydrogen in the case of FCVs.

If a manufacturer exceeds their cumulative 200,000 or 300,000 vehicle production cap, the global warming emissions scoring for grid-electricity miles for EVs and PHEVs will include the power plant emissions associated with the electricity production and delivery to the vehicle. (Hydrogen production and delivery emissions will be included for FCVs.) A recent Wall Street Journal article indicated that the power plant emissions accounting would be phased in; in fact, however, the electricity production emissions are applied to an automaker’s EV and PHEVs as soon as they go over the cumulative production cap.

In the final rule, EPA establishes a national grid electricity production factor for greenhouse gases—including CO2, CH4 and N2O—and coverts it to CO2-equivalent. The national factor, 0.642 gCO2e/Wh, is based on 2005 data of the average mix of power plants producing electricity. (This is a short-term solution to the complex modeling of the power sector and the marginal emissions associated with vehicle charging today and into the future when these cars will still be on the road.) EPA’s upstream accounting also includes emissions associated with the extraction, processing and transportation of feedstocks (like coal and natural gas) to the power plant and the agency accounts for losses that occur in electricity transmission and during vehicle charging.

Two more steps are needed to get a complete EV emissions rating. First, the grid emissions factor is multiplied by the vehicle’s efficiency (in Wh/mi). Second, the resulting gCO2/mi value is adjusted to account for the fact that EPA tailpipe emissions compliance calculations for internal combustion engines do not account for the production of gasoline and this adjustment allows for an apples-to-apples comparison with petroleum-only vehicles.

After all the complicated math is done, the electric-drive scoring process provides a reasonable initial assessment of EV/PHEV greenhouse gas performance.