This memo compares projected outcomes for California's Cap-and-Invest Program under the current California–Québec market against outcomes under an expanded market linked with Washington. Results are produced with Greenline Insights' Allowance Market Simulator using California program parameters certified against the amendments adopted by CARB in Spring 2026, with household and revenue effects estimated through TRACE, Greenline's economic-incidence framework. The comparison covers 2027 through 2045, the anticipated period of linked operation.

Under a central case, adding Washington modestly tightens California's allowance market. Allowance prices rise by approximately $3.80 per metric ton on average over the study period, peaking at a $6.71 differential in 2031. Prices remain well within California's price rails throughout: in no scenario examined does the market draw reserve allowances or issue price ceiling units.

Because prices are modestly higher under linkage, in-state abatement increases and California's cumulative covered emissions fall by roughly 77 million metric tons, while combined emissions across the two states fall by roughly 45 million metric tons. Expanded linkage also strengthens program outcomes for California, with cumulative GGRF revenue rising by $1.8 billion and household affordability improving.