MGE expects to recover its regulatory assets and return its regulatory liabilities through rates charged to customers based on PSCW decisions made during the ratemaking process or based on PSCW long-standing policies and guidelines. The adjustments to rates for these regulatory assets and liabilities will occur over the periods either specified by the PSCW or over the corresponding period related to the asset or liability. Management believes it is probable that MGE will continue to recover from customers the regulatory assets described above based on prior and current ratemaking treatment for such costs. All regulatory assets for which a cash outflow had been made are earning a return.

Asset Retirement Obligation

See Footnote 18 for further discussion.

Conservation Costs

MGE has received regulatory treatment for certain conservation expenditures. The expenditures are used for Focus on Energy programs, which is Wisconsin's statewide energy efficiency and renewable resource program, to promote energy efficiency on the customer's premises. Costs for Focus on Energy programs are estimated in MGE's rates utilizing escrow accounting. The escrow accounting allows the utility to true-up its actual costs incurred and reflect the amount of the true-up in its next rate case filing.

Debt Related Costs

This balance includes debt issuance costs of extinguished debt and other debt related expenses, including make-whole premiums. The PSCW has allowed rate recovery on unamortized issuance costs for extinguished debt facilities. When the facility replacing the old facility is deemed by the PSCW to be more favorable for the ratepayers, the PSCW will allow rate recovery of any unamortized issuance costs related to the old facility. These amounts are recovered over the term of the new facility.

Derivatives

MGE has physical and financial contracts that are accounted for as derivatives. The amounts recorded for the net mark-to-market value of the commodity based contracts is offset with a corresponding regulatory asset or liability because these transactions are part of the PGA or fuel rules clause authorized by the PSCW. A significant portion of the recorded amount is related to a purchased power agreement that provides MGE with firm capacity and energy during a base term that began on June 1, 2012, and ends on May 31, 2022. See Footnote 14 for further discussion.

Tax Recovery Related to AFUDC Equity

AFUDC equity represents the after-tax equity cost associated with utility plant construction and results in a temporary difference between the book and tax basis of such plant. It is probable under PSCW regulation that MGE will recover in future rates the future increase in taxes payable represented by the deferred income tax liability. The amounts will be recovered in rates over the depreciable life of the asset for which AFUDC was applied. Tax recovery related to AFUDC equity represents the revenue requirement related to recovery of these future taxes payable, calculated at current statutory tax rates.

Unfunded Pension and Other Postretirement Liability

MGE is required to recognize the unfunded status of defined benefit pension and other postretirement pension plans as a net liability or asset on the balance sheet with an offset to a regulatory asset or liability. The unfunded status represents future expenses that are expected to be recovered in rates. See Footnote 13 for further discussion.

Deferred Fuel Savings

The fuel rules require the PSCW and Wisconsin utilities to defer electric fuel-related costs that fall outside a symmetrical cost tolerance band. Any over/under recovery of the actual costs is determined on an annual basis and is adjusted in future billings to electric retail customers. See Footnote 8.b. for further discussion.

Elm Road

Costs associated with Elm Road are estimated in MGE's rates utilizing escrow accounting and include costs for lease payments, management fees, community impact mitigation, and operating costs. Costs are collected in rates over a one to two year period.

Income Taxes

Excess deferred income taxes result from past taxes provided at rates higher than current rates. The regulatory liability and deferred investment tax credit reflects the revenue requirement associated with the return of these tax benefits to customers.

Changes in income taxes are generally passed through in customer rates for the regulated utility. The one-time 2017 impact on timing differences related to income taxes passed through to customer rates of the Tax Act was recorded as a regulatory liability. The amount and timing of the cash impacts will depend on the period over which certain income tax benefits are provided to customers, which will be subject to review by the PSCW. A portion of the regulatory liability will be returned to customers based on a mandated timeframe dictated by applicable tax laws. See Footnote 12 for further information.

Non-ARO Removal Costs

In connection with accounting for asset retirement obligations, companies are required to reclassify cumulative collections for non-ARO removal costs as a regulatory liability, with an offsetting entry to accumulated depreciation. Under the current rate structure, these removal costs are being recovered as a component of depreciation expense.

Pension and Other Postretirement Service Costs

The FASB issued authoritative guidance within the codification's Compensation-Retirement Benefits topic that, beginning January 1, 2018, only allows the service cost component of net periodic benefit cost to be eligible for capitalization within the consolidated balance sheets. Under the current rate structure, non-service cost components of net periodic benefit cost are being recovered as a component of depreciation expense. MGE has regulatory treatment and recognizes regulatory assets or liabilities for timing differences between when net periodic benefit costs are recovered and when costs are recognized. See Footnote 13 for further discussion.

Purchased Gas Adjustment

MGE's natural gas rates are subject to a fuel adjustment clause designed to recover or refund the difference between the actual cost of purchased gas and the amount included in rates. Differences between the amounts billed to customers and the actual costs recoverable are deferred and recovered or refunded in future periods by means of prospective monthly adjustments to rates.

Renewable Energy Credits

MGE receives renewable energy credits from certain purchase power agreements. The value of the credits are recorded as inventory and expensed when the credit is redeemed or expired. A regulatory liability has been established for the value of the renewable energy credits included in inventory. In Wisconsin, renewable energy credits expire four years after the year of acquisition.

Transmission Costs

The current accounting treatment for transmission costs allows MGE to reflect any differential between transmission costs reflected in rates and actual costs incurred in its next rate filing.