FAQs about electricity and the environment

The regional average is the average of emissions from power plants that are part of the Midwest Reliability Organization (MRO). MRO is a region in the North American Electric Reliability Corporation that includes Minnesota, Wisconsin, Iowa, Nebraska, South Dakota, North Dakota, and small areas in Montana and Michigan. The emissions data for MRO was taken from an EPA database of power plant emissions called eGRID. This searchable database contains data on emissions of carbon dioxide, sulfur dioxide, nitrogen oxides and mercury emissions data from power plants nationwide. The MPCA calculated the regional average for particulate matter using PM10 emissions data for five states (Minnesota, North Dakota, South Dakota, Iowa, and Wisconsin). These data reported total PM10 emissions in EPA's National Emission Trends database for the 4911 SIC code (electric services). As EPA updates the eGRID database, the MPCA will provide an updated regional average for all five pollutants to the utilities for use in their brochures. The emissions rate is calculated in units of pounds of pollutant per 1000 kilowatt-hours generated.

Older data from eGRID is for the Mid-Continent Area Power Pool (MAPP, an association that includes electric utilities located in Minnesota, North Dakota, South Dakota, Nebraska, Alberta, Saskatchewan, and parts of Wisconsin, South Dakota and Iowa. (Emissions from electric generation in Alberta and Saskatchewan are not included in the regional average calculation because there is not a common U.S./Canada emissions database.)

In 2005, the Midwest Reliability Organization (MRO) generated electricity from a variety of fuels, and averaged 73% coal in its generation resource mix, compared to a national average of 50% coal. The table below compares average emissions of the MRO region (which Minnesota is a part of) with the United States as a whole.

(Year 2005 eGRID Data)


Power control area














MRO (lb/1000KW-hr)





US total (lb/1000KW-hr)





All utilities must meet state and federal emissions and air quality standards. A utility that has emissions higher than the regional average may have room for improvement in reducing its emissions. The regional average of the power pool (Midwest Reliability Organization (MRO)) that all Minnesota utilities belong to is higher than many in other parts of the nation.

Sulfur dioxide, carbon dioxide, and nitrogen oxides are measured continuously at the largest utilities. (Measuring devices are located in the exhaust stacks.) PM emissions rate are measured about one or two times every five years during a test run and the results are used to project emissions for the entire year. The mercury emission rate can be measured during a test run or estimated based on knowing the mercury content of the coal burned and the type of control equipment.

All large power plants are required to do computerized projections of pollutant concentrations in the air at locations up to 30 miles away under all weather conditions. This is called computer modeling. If the modeled concentrations do not meet outdoor air quality standards, then the power plant must make changes to bring the predicted concentrations within the standards. Power plants are also required to measure emissions from their stacks so that emission rates do not exceed permitted levels. Some large power plants are also required to monitor pollutant concentrations at locations in their vicinity.

Large power plants have tall stacks to disperse air pollutants over large distances. The taller the stack, the greater the dispersal distance and the lower the pollutant concentrations at the ground near the plant. All large coal-fired plants are required to show through air dispersion modeling that they do not exceed state and federal standards for outdoor air quality. These standards are designed to protect human health with a margin of safety. Federal law requires EPA to update the standards every 5 years based on the latest scientific studies. These standards could become stricter in the future as some scientific studies are showing health effects at levels below the current standards for some pollutants.

Science is always evolving and the more we study pollutants, the more we learn about what levels are considered safe. Generally, air quality standards have become stricter over the years. Some studies are finding health effects below the standards for pollutants such as fine particles. In addition, some pollutants are not regulated because we have no information about their effects or the information we have is not sufficient to develop standards. Overall, data show that air quality has improved over the last 30 years for most of the criteria pollutants (ozone, sulfur dioxide, nitrogen dioxide, particulate matter, lead, and carbon monoxide) at most locations. We have less information about other pollutants such as air toxics. (See the MPCA Web page for Air toxics in Minnesota).

The MPCA's primary role is to provide environmental information about the various types of electric generation – sources, emissions, environmental effects – to decisionmakers such as the legislature and Public Utilities Commission. Environmental considerations are one factor in deciding our electric generation sources and how their emissions may be controlled. MPCA is making greater efforts to provide decision makers with information so environmental considerations can play a larger role in energy resource choices. The MPCA has been supportive of Xcel's Metropolitan Emissions Reduction Project. This project calls for switching the Riverside (Minneapolis) and High Bridge (St. Paul) power plants from coal to natural gas and updating the Allen S. King plant in Oak Park Heights by adding new pollution control equipment. This project will lower total state emissions of SO2 by 16.8%, NOx by 3.1% and mercury by 4.9%. (See Xcel Energy's Metropolitan Emission Reduction Proposal on this website for the full report.)

If you participate in this program, the electricity you use will be the same as your neighbor's because the electricity is on the same transmission grid system. However, you will be making a difference because the dollars you spend will go to support more wind-produced electricity going into the system. (For more information refer to the section on the How Can Minnesota Citizens Make a Difference page titled “Wind Power Options for Utility Customers”.)

The Public Utilities Commission has ordered that each utility retain the records supporting the claims in their brochures for two years. Utilities involved in this process have promised to make a good faith effort.