[en] Two recently released reports by the Federal Energy Regulatory Commission (FERC) and the Department of Energy (DOE) are urging state commissions to proceed slowly when it comers to incorporating environmental externalities of electric generation in integrated resource plans (IRP). The FERC report, Report on Section 808: Renewable Energy and Energy Conservation Incentives of the Clean Air Act Amendments of 1990, takes issue with earlier studies by Pace University and the Tellus Institute. Those reports attempted to quantify, among other things, environmental damage estimates of SO₂, NO_x, and CO₂ emitted by coal, gas, and oil plants, and to calculate damage costs associated with nuclear plants. Generally, the FERC report criticized both studies for using externality values for the three pollutants that exceed most other estimates in current use. (The Pace study assumed externality values of $4,060 a ton for SO2, $1,640 a ton for NO_x, and $13.64 a ton for CO₂, while the Tellus Institute study assumed values of $1,500 a ton for SO₂ and $22 a ton for CO₂). The FERC report says a shortcoming of these adder studies (so-named because they add an externality value to the cost of generating alternatives considered by utilities and their regulators in IRP proceedings) is that they do not conform to the principles of estimating externalities based on a damage function approach. In particular, FERC says, they rely on control cost estimates rather than environmental damage estimates