The confluence of several pending environmental rulemakings will require billions of dollars of investment across the industry and changes in the operation of facilities. These changes may lead to retirement of some facilities, and there has been much debate about their potential effects on electricity reliability. Only very exceptional circumstances would trigger supply disruptions; however, the changes may affect electricity prices, the generation mix, and industry revenues. Coincident with these new rules, expectations about natural gas prices and future electricity demand growth are changing in ways that also will have substantial effects on the industry. This paper addresses these two sets of issues using a detailed simulation model of the U.S. electricity market. The findings suggest that recent downward adjustments in natural gas prices and electricty demand projections have a substantially larger impact on electricity prices and generation mix than do the new environmental rules.