Under current CAFE (Corporate Average Fuel Economy) laws, the standard for passenger cars is holding steady at 27.5 mpg. The standard for light trucks increased in 2005 to 21 mpg from the previous 20.7 mpg, and will increase to an expected 24 mpg in 2011 under the new Reformed CAFE rule. Because Reformed CAFE establishes different goals for different automakers, it’s difficult to specify a precise average target. (Earlier post.)

The primary Senate bill that is emerging from the Committee on Commerce, Science, and Transportation incorporates S.357, originally sponsored by Senator Dianne Feinstein (D-CA). This bill calls for combined fleet (cars and light trucks) fuel economy of 35 mpg by 2020, with a 4% annual increase thereafter. The bill sets initial milestones for 2010 of 29.5 mpg for passenger cars and 23.5 mpg for light trucks—the latter being slightly less than the expected average for 2010 under Reformed CAFE. The bill also brings back the concept of the 4% annual increase after 2020.

Automakers have deemed this proposal unworkable, and are leaning toward a more lenient proposal being developed in the House by Representatives Rick Boucher (D-VA) and John Dingell (D-MI). This House proposal mirrors an alternative bill for the Senate being developed by Michigan’s two senators, Carl Levin (D-MI) and Debbie Stabenow (D-MI).

Under the Boucher/Dingell and Levin/Stabenow plans, cars and trucks would maintain two different fuel economy standards. The standard for cars would increase to 36 mpg by 2022; the standard for trucks would increase to 30 mpg by 2025.

The Boucher/Dingell bill also bars states from implementing greenhouse gas limits on vehicles. This would preclude California and the other states adopting California regulations from acquiring the waiver from the EPA required to implement the greenhouse gas limits on new vehicles established in AB1493. (Earlier post.)

AB1493 does not establish fuel economy standards per se, only limits on total greenhouse gas emissions from the vehicle. Using the EPA’s figures for average carbon dioxide emissions resulting from gasoline (8,788 grams per gallon), we can calculate the approximate impact AB1493 would have on fuel economy.

(Because gasoline and diesel have different carbon levels, the resulting fuel economy requirements to meet a specific carbon target will vary. In other words, a 250 g/mi limit on carbon dioxide results in required gasoline fuel economy of 35 mpg, and required diesel fuel economy of 40 mpg. Here we just approximate the gasoline fuel economy values.)

California divides its light-duty vehicles into two categories: passenger cars and small trucks and SUVs (PC/LDT1); and larger trucks and SUVs (LDT2), each with a different standard. Based on the greenhouse gas emissions targets in AB1493, fuel economy for PC/LDT1 would need to increase to 42.9 mpg by 2016, while fuel economy for the LDT2 would need to increase to 26.5 mpg by 2016. That produces a very approximate (gasoline) fleet average of 35 mpg—the same fleet target as S.357, but 4 years earlier.

A Senate floor debate on the Commerce Committee bill and the Levin/Stabenow alternative is due to start next week.

The House Energy and Air Quality subcommittee (Boucher is the Chair) will consider amendments to the Boucher/Dingell bill next week, and the full committee will debate and vote on the measure the week of June 18.