Carbon dioxide (CO2) emissions from electricity generation in 2015 were at their lowest lowest since 1993, 21% below their 2005 level, thanks to generation from natural gas and renewables displacing that of coal. Electricity from natural gas exceeded coal-based power for 7 months in 2015. Overall demand for electricity remained steady over the decade in response to greater efficiency balancing out population increases.
The source of electricity is usually determined by available capacity and relative operating costs. With regard to capacity, natural gas and renewable energy have dominated additions and most retirements have been coal units. In terms of operating costs, the drop in natural gas prices and advancements in natural gas-related technology have made the fuel a more cost-effective substitute for coal. Increased regulation concerning air pollution, mercury runoff, and CO2 emissions have also increased operating costs for coal while creating doubts about its prospects in the long-run.
Compared to coal plants, a combined-cycle natural gas plant is capable of producing the same amount of electricity without as much heat loss or CO2 emissions. Natural gas generation emits roughly 40% of the CO2 coal generation would.
Trends in CO2 emissions from electricity generation through 2040 depend significantly on whether or not the Clean Power Plan (CPP) rule is implemented. The CPP would have an especially significant effect on coal usage as evidenced in the EIA’s Reference case assuming the EPA enforces the final CPP rule and the No CPP case where the rule never comes into effect.
In the Reference case, power-sector emissions are projected to be 28% lower than the 2005 level in 2022. The reduction in CO2 emissions compared with 2005 levels is about 35% from 2030–40.
In the No CPP case, power-sector CO2 emissions are 7% higher than in the Reference case in 2022 and about 25% higher in 2030 and beyond.
The power sector accounts for 36% of total energy-related CO2 emissions, but its share falls to 31% by 2030, below the share held by the transportation sector, in the Reference case. Its share of emissions remains unchanged in the No CPP case. Keep in mind that the EIA does not take into account major technological changes such as the introduction of mass-market electric and/or self-driving cars. Tesla Motors has planned to sell over 500,000 electric cars in 2018; it bumped up that schedule from an expected date in 2020. Most major car companies and even some technology companies like Apple will be selling competing electric vehicles before 2025.
In the Reference case, reductions in CO2 emissions to comply with the CPP are primarily achieved by switching from coal to natural gas, solar, and wind. Increased energy efficiency is also expected to contribute to lower fuel use and emissions.
Coal retirements are expected regardless of the CPP’s enforcement or lack there of. Retirements are already high due to competition from natural gas units and stricter environmental regulations. And retirements of coal are expected to spike in 2016 because the final deadline for the EPA’s Mercury and Air Toxics Standards (MATS) occurred in April. The standards themselves survived legal challenges that were resolved with the Supreme Court ruling in favor of EPA enforcement.
In the Reference case, the remaining coal-fired generation capacity is used less intensively over time. The combination of retirements and lower utilization is expected to cause coal consumption in the electric power sector to decline by 34% from 2015 to 2040 in the Reference case. The electric power sector accounts for more than 90% of total U.S. coal consumption.