There are at least two approaches to estimate the impact of the Climate Commitment Act on gas prices. They suggest price impacts of 19 to 61 cents per gallon, with the midpoint (about 40 cents per gallon) being a decent point estimate.

The first approach is to look at the change in gas prices in Washington State compared to other jurisdictions. (Oregon is an especially good comparison because petroleum products in western Oregon and western Washington come from the same refineries, so differences in the spread between Oregon and Washington should reflect changes in policy such as the CCA.) Here is my collection of data from AAA and EIA. Row 144 shows that EIA data (comparing Washington State with a group including Arizona, Oregon, and Nevada) suggests a price impact from the Climate Commitment Act of 35 cents per gallon. It also shows that AAA data (comparing Washington State with many other states) suggests a price impact from the Climate Commitment Act of 19-24 cents per gallon (versus Oregon, Arizona, or Nevada), with a high of 61 cents per gallon (versus Idaho) and a low of -8 cents per gallon (versus California, which has its own stringent climate policy and is consequently not a good baseline for comparison).

The second approach is based on economics and chemistry. Auction prices in the first four auctions have been $31 – $62 per ton CO2, which translates (based, e.g., the RFF calculator) to 28 – 55 cents per gallon of gasoline. The weighted average—see gory details below—was $53 per ton CO2, which translates to 47 cents per gallon of gasoline. That’s the chemistry. The economics, to quote a 2011 NBER paper, is that there is “complete pass-through… to consumers” of such charges. It is theoretically possible that refineries or other supply-side entities are sharing the financial burden, but the empirical evidence is that consumers bear the entire burden.  (The basic idea here is that supply in Washington State is “elastic”: try to cut into BP’s profit margins in Washington State and they would rather cut back their sales in Washington State and sell more in Idaho or New York or Calcutta.)

Gory details per Dept of Ecology: Auction 1 sold 6.185m current permits at $48.50. Auction 2 sold 8.585m current permits at $56.01 and 2.45m advance permits at $31.12. Auction 3 sold 8.585m current permits at $63.03. Auction 4 sold 7.142m current permits at $51.89 and 2.45m advance permits at $45.00.