This paper introduces a simple system-level emissions model suitable f
or regulators to design efficient integrated resource planning rules.
Given choices that include life-extending existing capacity, investing
in new generation, and demand-side management, it identifies cost-eff
ective pollution reduction strategies. A set of examples using aggrega
ted regional data shows that superior solutions differ across pollutan
ts and regions. This implies that policy prescriptions should account
for differences in existing capacity characteristics in order to be ef
ficient. Specifically, regulations should not focus only on marginal c
apacity choices, but should compare complete resource portfolios.