Commitments and Contingencies	3 Months Ended
Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies - MGE Energy and MGE. a. Environmental. MGE Energy and MGE are subject to frequently changing local, state, and federal regulations concerning air quality, water quality, land use, threatened and endangered species, hazardous materials handling, and solid waste disposal. These regulations affect the manner in which they conduct their operations, the costs of those operations, as well as capital and operating expenditures. Regulatory initiatives, proposed rules, and court challenges to adopted rules, have the potential to have a material effect on our capital expenditures and operating costs. These initiatives, proposed rules, and court challenges include: EPA's Proposed Effluent Limitations Guidelines (ELG) and Standards for Steam Electric Power Generating Point Source Category The EPA published a proposed rule in June 2013 that would amend the current ELG rule and lower the existing permissible water discharge of metals and other pollutants in wastewater from new and existing steam electric generation plants. The proposed rule mostly covers certain air pollution control systems and ash handling systems at coal-burning power plants with units greater than 50 megawatt (MW) generation capacity. The EPA is under a consent decree to finalize the rule by September 2015. Once finalized, the rule will apply to power plants as they renew their WPDES permits beginning in July 2017. Based on our current evaluation of the proposed rule and its alternatives, our Elm Road Units and Columbia plant may need to add treatment systems or additional equipment, and those additions may be significant. However, MGE cannot estimate those costs with any certainty until we are able to evaluate the final version of this rule. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects. EPA Cooling Water Intake Rules (Section 316(b)) Section 316(b) of the CWA requires that the cooling water intake structures at electric power plants meet best available technology standards so that mortality from entrainment (drawing aquatic life into a plant's cooling system) and impingement (trapping aquatic life on screens) are reduced. The EPA finalized its 316(b) rule for existing facilities in 2014. Section 316(b) requirements are implemented in Wisconsin through modifications to plants' WPDES permits, which govern plant water discharges. WDNR is currently developing rules to implement the EPA 316(b) rule. Our WCCF facility already employs a system that meets the 316(b) rule. Our Blount plant has conducted studies showing that it will likely be in compliance with this rule. The operator of our Columbia plant plans to conduct an intake study to demonstrate compliance with this rule and/or identify design criteria needed to meet the new rule requirements prior to Columbia's 2017 permit renewal. The exact requirements at Blount and Columbia, however, will not be known until the WNDR finalizes its rule, approves the operators' approach, and those sites' permits are modified to account for this rule. Nonetheless, MGE expects that the 316(b) rule will not have material effects on its existing plants. EPA's Greenhouse Gas (GHG) Reduction Guidelines under the Clean Air Act 111d Rule In June 2014, the EPA developed a proposed rule called the Clean Power Plan that set guidelines for states to use in developing plans to control GHG emissions from existing fossil fuel fired electric generating units (EGUs). The EPA's proposal includes reductions in GHG emissions from EGUs by a national average of 30% by 2030 as measured from a 2012 baseline. Each state is given its own emission reduction targets to meet this goal, and States' goals can be higher or lower than the national average. The State of Wisconsin's reduction goal is 34%. These targets are expressed as a "rate-based" emission average to be achieved by the combined fleet of EGUs within the state. States would be expected to develop, submit and implement a plan for the reduction goals, and make "meaningful progress" towards these reductions by 2020 and to meet their respective targets by 2030. The EPA's rule is expected to be finalized mid-summer 2015. States will then have up to two years to prepare their compliance plans. While there is currently no certainty regarding the terms of the final rule, it is reasonable to assume that this rule will have a material impact on MGE. The parameters of the final rule, however, will determine the extent to which this rule will affect MGE. National Ambient Air Quality Standards (NAAQS) The EPA's NAAQS regulations have been developed to set ambient levels of six pollutants to protect sensitive populations (primary NAAQS) and the environment (secondary NAAQS) from the negative effects of exposure to these pollutants at higher levels. MGE is following developments for several NAAQS, including for particulate matter, nitrogen dioxide, sulfur dioxide, and ozone. Further discussion on sulfur dioxide and ozone NAAQS follows. For additional information on the NAAQS process, see Footnote 18.d. of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2014 Annual Report on Form 10-K. Sulfur Dioxide (SO₂) NAAQS The EPA's new 1-hour SO₂ NAAQS has been in place since 2010 and initial attainment/nonattainment designations by states were due in 2013. However, the EPA was sued by environmental groups for not timely and properly making these designations. In March 2015, the EPA entered into a court-approved consent decree requiring 1-hour SO₂ attainment/nonattainment area designations to be completed in three phases extending out until 2020. States must submit their first designation proposals in September 2015 encompassing those areas that contain large stationary sources of SO₂ (sources that emit over a threshold mass of SO₂, and/or over a threshold emissions rate). The EPA must make final designation determinations for these areas by July 2016. In March 2015, MGE's Columbia plant was identified in the Federal Register as meeting the criteria of a large stationary source of SO₂ (based on 2012 data). As such, the State of Wisconsin must submit an attainment/nonattainment area designation for Columbia County (the county in which the Columbia plant resides). Since the 2012 data was collected, Columbia has installed pollution control equipment that has lowered its total SO₂ emissions and its SO₂ emissions rate. However, we will not know with any certainty if Columbia County will be determined to be in attainment until the State of Wisconsin completes its attainment/nonattainment demonstration. The outcome of this designation may have an adverse effect on the operation of the Columbia plant. MGE will monitor and participate in developments with the Columbia County designation process. Ozone NAAQS MGE is monitoring developments in the EPA's revision of the Ozone NAAQS rule. In November 2014, the EPA published proposed regulations to lower the Ozone NAAQS to between 65 to 70 parts per billion (ppb). In this proposed rule, the EPA has stated they are also considering leaving the standard at its current level of 75 ppb, or lowering it further to 60 ppb. The EPA is seeking comments on these options. In addition, the EPA is proposing a secondary ozone standard that would use a new index to measure ecosystem and vegetation effects. It is not clear how this secondary standard would affect sources. Milwaukee County (where our Elm Road Units are located) and Dane and Columbia Counties (where several of our facilities are located) may not meet the Ozone NAAQS if it is lowered to 70 ppb or below. The EPA plans to have a final Ozone NAAQS rule completed by the end of 2015. MGE will continue to monitor rule developments and subsequent state actions and implementation plans. EPA's Cross-State Air Pollution Rule In July 2011, the EPA finalized its Cross-State Air Pollution Rule (CSAPR) as a court-ordered replacement for its Clean Air Interstate Rule (CAIR) that had been remanded in 2008. CSAPR is an interstate air pollution transport rule designed to reduce ozone and fine particulate matter (PM2.5) air levels in areas that the EPA has determined are being affected by pollution from neighboring and upwind states. CSAPR has been the subject of extensive litigation. Although many aspects of CSAPR have been upheld on appeal, the litigation has delayed implementation and created uncertainty. In late 2014, the EPA tolled CSAPR's original compliance deadlines by three years and MGE's affected facilities must now meet their Phase I reduction obligations in 2015 and Phase II in 2017. However, the ongoing litigation leaves unresolved several residual issues that may affect whether, when, and how MGE's facilities will need to comply with CSAPR. Regardless, MGE expects to be able to meet CSAPR requirements at all of our applicable facilities by applying reductions achieved from recent pollution control installations and early reduction efforts. We will continue to monitor developments. Clean Air Visibility Rule (CAVR) Columbia may be subject to the best available retrofit technology (BART) regulations, a subsection of the EPA's Clean Air Visibility Rule (CAVR), which may require pollution control retrofits. Columbia's pollution control upgrades and the EPA's stance that compliance with the CSAPR equals compliance with BART should mean that Columbia will not need to do additional work to meet BART requirements. At this time, however, the BART regulatory obligations, compliance strategies, and costs remain uncertain due to the legal uncertainty surrounding CSAPR. EPA's Coal Combustion Residuals Rule In December 2014, the EPA finalized its Disposal of Coal Combustion Residuals from Electric Utilities rule. The rule will go into effect six months after it is published in the Federal Register. The EPA has delayed publication of this rule and has indicated that it plans to publish the rule during the second quarter of 2015. The rule provides that coal ash will be regulated as a solid waste and defines what ash use activities would be considered beneficial use of coal ash. The rule also regulates landfills, ash ponds, and other surface impoundments for coal combustion residuals (CCRS or coal ash) by regulating their design, location, monitoring, and operation. Landfills and impoundments that cannot meet design criteria will need to formally close within defined timeframes. The Columbia and Elm Road Units co-owners and plant operators are evaluating the final rule to determine what changes may be necessary at those facilities and the associated timeframes. We anticipate that some design and operational changes may need to be made at these facilities. Preliminary review for our Elm Road facility has indicated that the costs may not be significant. We are still evaluating the rule’s full effects at Columbia. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects. Columbia Based upon current available information, compliance with various environmental requirements and initiatives is expected to result in significant additional operating and capital expenditures at Columbia as noted below. Columbia Clean Air Act Litigation Columbia is a coal-fired generating station operated by WPL in which WPL, WPSC, and MGE have ownership interests. In December 2009, the EPA sent a Notice of Violation (NOV) to MGE as one of the co-owners of Columbia. The NOV alleged that WPL and the Columbia co-owners failed to comply with appropriate pre-construction review and permitting requirements and, as a result, violated the Prevention of Significant Deterioration program requirements, Title V Operating Permit requirements of the CAA, and the Wisconsin SIP. In April 2013, the EPA filed a lawsuit against the co-owners of Columbia asserting similar allegations. In September 2010 and April 2013, the Sierra Club filed civil lawsuits against WPL alleging violations of the CAA at Columbia and other Wisconsin facilities operated by WPL. In June 2013, the court approved and entered a consent decree entered by the EPA, Sierra Club, and the co-owners of Columbia to resolve these claims, while admitting no liability. One of the requirements of the consent decree requires installation of a SCR system at Columbia Unit 2 by December 31, 2018. Installation of the SCR has been approved by the PSCW. MGE's share of the projected cost for the SCR system is approximately $30-$40 million. In addition, the consent decree establishes emission rate limits for SO₂, NO_x, and particulate matter and annual plant-wide emission caps for SO₂ and NO_x. MGE intends to seek recovery in rates of the costs associated with its compliance with the terms of the final consent decree and currently expects to recover any material compliance costs. b. Legal Matters. MGE is involved in various legal matters that are being defended and handled in the normal course of business. MGE maintains accruals for such costs that are probable of being incurred and subject to reasonable estimation. The accrued amount for these matters is not material to the financial statements.

Commitments and Contingencies - MGE Energy and MGE.

a. Environmental.

MGE Energy and MGE are subject to frequently changing local, state, and federal regulations concerning air quality, water quality, land use, threatened and endangered species, hazardous materials handling, and solid waste disposal. These regulations affect the manner in which they conduct their operations, the costs of those operations, as well as capital and operating expenditures. Regulatory initiatives, proposed rules, and court challenges to adopted rules, have the potential to have a material effect on our capital expenditures and operating costs. These initiatives, proposed rules, and court challenges include:

EPA's Proposed Effluent Limitations Guidelines (ELG) and Standards for Steam Electric Power Generating Point Source Category

The EPA published a proposed rule in June 2013 that would amend the current ELG rule and lower the existing permissible water discharge of metals and other pollutants in wastewater from new and existing steam electric generation plants. The proposed rule mostly covers certain air pollution control systems and ash handling systems at coal-burning power plants with units greater than 50 megawatt (MW) generation capacity. The EPA is under a consent decree to finalize the rule by September 2015. Once finalized, the rule will apply to power plants as they renew their WPDES permits beginning in July 2017.

Based on our current evaluation of the proposed rule and its alternatives, our Elm Road Units and Columbia plant may need to add treatment systems or additional equipment, and those additions may be significant. However, MGE cannot estimate those costs with any certainty until we are able to evaluate the final version of this rule. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects.

EPA Cooling Water Intake Rules (Section 316(b))

Section 316(b) of the CWA requires that the cooling water intake structures at electric power plants meet best available technology standards so that mortality from entrainment (drawing aquatic life into a plant's cooling system) and impingement (trapping aquatic life on screens) are reduced. The EPA finalized its 316(b) rule for existing facilities in 2014. Section 316(b) requirements are implemented in Wisconsin through modifications to plants' WPDES permits, which govern plant water discharges. WDNR is currently developing rules to implement the EPA 316(b) rule.

Our WCCF facility already employs a system that meets the 316(b) rule. Our Blount plant has conducted studies showing that it will likely be in compliance with this rule. The operator of our Columbia plant plans to conduct an intake study to demonstrate compliance with this rule and/or identify design criteria needed to meet the new rule requirements prior to Columbia's 2017 permit renewal. The exact requirements at Blount and Columbia, however, will not be known until the WNDR finalizes its rule, approves the operators' approach, and those sites' permits are modified to account for this rule. Nonetheless, MGE expects that the 316(b) rule will not have material effects on its existing plants.

EPA's Greenhouse Gas (GHG) Reduction Guidelines under the Clean Air Act 111d Rule

In June 2014, the EPA developed a proposed rule called the Clean Power Plan that set guidelines for states to use in developing plans to control GHG emissions from existing fossil fuel fired electric generating units (EGUs). The EPA's proposal includes reductions in GHG emissions from EGUs by a national average of 30% by 2030 as measured from a 2012 baseline. Each state is given its own emission reduction targets to meet this goal, and States' goals can be higher or lower than the national average. The State of Wisconsin's reduction goal is 34%. These targets are expressed as a "rate-based" emission average to be achieved by the combined fleet of EGUs within the state. States would be expected to develop, submit and implement a plan for the reduction goals, and make "meaningful progress" towards these reductions by 2020 and to meet their respective targets by 2030.

The EPA's rule is expected to be finalized mid-summer 2015. States will then have up to two years to prepare their compliance plans. While there is currently no certainty regarding the terms of the final rule, it is reasonable to assume that this rule will have a material impact on MGE. The parameters of the final rule, however, will determine the extent to which this rule will affect MGE.

National Ambient Air Quality Standards (NAAQS)

The EPA's NAAQS regulations have been developed to set ambient levels of six pollutants to protect sensitive populations (primary NAAQS) and the environment (secondary NAAQS) from the negative effects of exposure to these pollutants at higher levels. MGE is following developments for several NAAQS, including for particulate matter, nitrogen dioxide, sulfur dioxide, and ozone. Further discussion on sulfur dioxide and ozone NAAQS follows. For additional information on the NAAQS process, see Footnote 18.d. of Notes to Consolidated Financial Statements under Item 8, Financial Statements and Supplementary Data, of MGE Energy's and MGE's 2014 Annual Report on Form 10-K.

Sulfur Dioxide (SO₂) NAAQS

The EPA's new 1-hour SO₂ NAAQS has been in place since 2010 and initial attainment/nonattainment designations by states were due in 2013. However, the EPA was sued by environmental groups for not timely and properly making these designations. In March 2015, the EPA entered into a court-approved consent decree requiring 1-hour SO₂ attainment/nonattainment area designations to be completed in three phases extending out until 2020. States must submit their first designation proposals in September 2015 encompassing those areas that contain large stationary sources of SO₂ (sources that emit over a threshold mass of SO₂, and/or over a threshold emissions rate). The EPA must make final designation determinations for these areas by July 2016.

In March 2015, MGE's Columbia plant was identified in the Federal Register as meeting the criteria of a large stationary source of SO₂ (based on 2012 data). As such, the State of Wisconsin must submit an attainment/nonattainment area designation for Columbia County (the county in which the Columbia plant resides). Since the 2012 data was collected, Columbia has installed pollution control equipment that has lowered its total SO₂ emissions and its SO₂ emissions rate. However, we will not know with any certainty if Columbia County will be determined to be in attainment until the State of Wisconsin completes its attainment/nonattainment demonstration. The outcome of this designation may have an adverse effect on the operation of the Columbia plant. MGE will monitor and participate in developments with the Columbia County designation process.

Ozone NAAQS

MGE is monitoring developments in the EPA's revision of the Ozone NAAQS rule. In November 2014, the EPA published proposed regulations to lower the Ozone NAAQS to between 65 to 70 parts per billion (ppb). In this proposed rule, the EPA has stated they are also considering leaving the standard at its current level of 75 ppb, or lowering it further to 60 ppb. The EPA is seeking comments on these options. In addition, the EPA is proposing a secondary ozone standard that would use a new index to measure ecosystem and vegetation effects. It is not clear how this secondary standard would affect sources. Milwaukee County (where our Elm Road Units are located) and Dane and Columbia Counties (where several of our facilities are located) may not meet the Ozone NAAQS if it is lowered to 70 ppb or below. The EPA plans to have a final Ozone NAAQS rule completed by the end of 2015. MGE will continue to monitor rule developments and subsequent state actions and implementation plans.

EPA's Cross-State Air Pollution Rule

In July 2011, the EPA finalized its Cross-State Air Pollution Rule (CSAPR) as a court-ordered replacement for its Clean Air Interstate Rule (CAIR) that had been remanded in 2008. CSAPR is an interstate air pollution transport rule designed to reduce ozone and fine particulate matter (PM2.5) air levels in areas that the EPA has determined are being affected by pollution from neighboring and upwind states.

CSAPR has been the subject of extensive litigation. Although many aspects of CSAPR have been upheld on appeal, the litigation has delayed implementation and created uncertainty. In late 2014, the EPA tolled CSAPR's original compliance deadlines by three years and MGE's affected facilities must now meet their Phase I reduction obligations in 2015 and Phase II in 2017. However, the ongoing litigation leaves unresolved several residual issues that may affect whether, when, and how MGE's facilities will need to comply with CSAPR. Regardless, MGE expects to be able to meet CSAPR requirements at all of our applicable facilities by applying reductions achieved from recent pollution control installations and early reduction efforts. We will continue to monitor developments.

Clean Air Visibility Rule (CAVR)

Columbia may be subject to the best available retrofit technology (BART) regulations, a subsection of the EPA's Clean Air Visibility Rule (CAVR), which may require pollution control retrofits. Columbia's pollution control upgrades and the EPA's stance that compliance with the CSAPR equals compliance with BART should mean that Columbia will not need to do additional work to meet BART requirements. At this time, however, the BART regulatory obligations, compliance strategies, and costs remain uncertain due to the legal uncertainty surrounding CSAPR.

EPA's Coal Combustion Residuals Rule

In December 2014, the EPA finalized its Disposal of Coal Combustion Residuals from Electric Utilities rule. The rule will go into effect six months after it is published in the Federal Register. The EPA has delayed publication of this rule and has indicated that it plans to publish the rule during the second quarter of 2015. The rule provides that coal ash will be regulated as a solid waste and defines what ash use activities would be considered beneficial use of coal ash. The rule also regulates landfills, ash ponds, and other surface impoundments for coal combustion residuals (CCRS or coal ash) by regulating their design, location, monitoring, and operation. Landfills and impoundments that cannot meet design criteria will need to formally close within defined timeframes.

The Columbia and Elm Road Units co-owners and plant operators are evaluating the final rule to determine what changes may be necessary at those facilities and the associated timeframes. We anticipate that some design and operational changes may need to be made at these facilities. Preliminary review for our Elm Road facility has indicated that the costs may not be significant. We are still evaluating the rule’s full effects at Columbia. Management believes compliance costs will be recovered in rates based on previous treatment of environmental compliance projects.

Columbia

Based upon current available information, compliance with various environmental requirements and initiatives is expected to result in significant additional operating and capital expenditures at Columbia as noted below.

Columbia Clean Air Act Litigation

Columbia is a coal-fired generating station operated by WPL in which WPL, WPSC, and MGE have ownership interests. In December 2009, the EPA sent a Notice of Violation (NOV) to MGE as one of the co-owners of Columbia. The NOV alleged that WPL and the Columbia co-owners failed to comply with appropriate pre-construction review and permitting requirements and, as a result, violated the Prevention of Significant Deterioration program requirements, Title V Operating Permit requirements of the CAA, and the Wisconsin SIP. In April 2013, the EPA filed a lawsuit against the co-owners of Columbia asserting similar allegations. In September 2010 and April 2013, the Sierra Club filed civil lawsuits against WPL alleging violations of the CAA at Columbia and other Wisconsin facilities operated by WPL. In June 2013, the court approved and entered a consent decree entered by the EPA, Sierra Club, and the co-owners of Columbia to resolve these claims, while admitting no liability. One of the requirements of the consent decree requires installation of a SCR system at Columbia Unit 2 by December 31, 2018. Installation of the SCR has been approved by the PSCW. MGE's share of the projected cost for the SCR system is approximately $30-$40 million. In addition, the consent decree establishes emission rate limits for SO₂, NO_x, and particulate matter and annual plant-wide emission caps for SO₂ and NO_x. MGE intends to seek recovery in rates of the costs associated with its compliance with the terms of the final consent decree and currently expects to recover any material compliance costs.