Regulation	9 Months Ended
Sep. 30, 2018
Regulated Operations [Abstract]
Regulation	Regulation General The rates and services of the Company are regulated by incorporated municipalities in Texas, the PUCT, the NMPRC and the FERC. Municipal orders, ordinances and other agreements regarding rates and services adopted by Texas municipalities are subject to review and approval by the PUCT. The FERC has jurisdiction over the Company's wholesale (sales for resale - full requirement customer) transactions, transmission service and compliance with federally-mandated reliability standards. The decisions of the PUCT, the NMPRC and the FERC are subject to judicial review. Texas Regulatory Matters 2015 Texas Retail Rate Case Filing. On August 10, 2015, the Company filed with the City of El Paso, other municipalities incorporated in its Texas service territory, and the PUCT in Docket No. 44941, a request for an annual increase in non-fuel base revenues ("2015 Texas Retail Rate Case"). On July 21, 2016, the parties to PUCT Docket No. 44941 filed the Joint Motion to Implement Uncontested Amended and Restated Stipulation and Agreement which was unopposed by the parties. On August 25, 2016, the PUCT issued the PUCT Final Order in Docket No. 44941 ("2016 PUCT Final Order"). Interim rates associated with the annual non-fuel base rate increase became effective on April 1, 2016. The additional surcharges associated with the incremental Four Corners Generating Station ("Four Corners") costs, rate case expenses and the relate back of rates to consumption on and after January 12, 2016, through March 31, 2016, were implemented on October 1, 2016. For financial reporting purposes, the Company deferred any recognition of the Company's request in its 2015 Texas Retail Rate Case until it received the 2016 PUCT Final Order on August 25, 2016. Accordingly, it reported in the third quarter of 2016 the cumulative effect of the 2016 PUCT Final Order, which related back to January 12, 2016. 2017 Texas Retail Rate Case Filing. On February 13, 2017, the Company filed with the City of El Paso, other municipalities incorporated in the Company's Texas service territory and the PUCT in Docket No. 46831, a request for an increase in non-fuel base revenues ("2017 Texas Retail Rate Case"). On November 2, 2017, the Company filed the Joint Motion to Implement Uncontested Stipulation and Agreement with the Administrative Law Judges for the 2017 Texas Retail Rate Case. On December 18, 2017, the PUCT issued the PUCT Final Order in Docket No. 46831 ("2017 PUCT Final Order"), which provides, among other things, for the following: (i) an annual non-fuel base rate increase of $14.5 million; (ii) a return on equity of 9.65%; (iii) all new plant in service as filed in the Company's rate filing package was prudent and used and useful and therefore is included in rate base; (iv) recovery of the costs of decommissioning Four Corners in the amount of $5.5 million over a seven year period beginning August 1, 2017; (v) the Company to recover reasonable rate case expenses of approximately $3.4 million through a separate surcharge over a three year period; and (vi) a requirement that the Company file a refund tariff if the federal statutory income tax rate, as it relates to the Company, is decreased before the Company files its next rate case. The 2017 PUCT Final Order also established baseline revenue requirements for recovery of future transmission and distribution investment costs (for which the Company may seek recovery after January 1, 2019, and for which the Company anticipates requesting recovery in the first quarter of 2019) and includes a minimum monthly bill of $30.00 for new residential customers with distributed generation, such as private rooftop solar. Additionally, the 2017 PUCT Final Order allows for the annual recovery of $2.1 million of nuclear decommissioning funding and establishes annual depreciation expense that is approximately $1.9 million lower than the annual amount requested by the Company in its initial filing. Finally, the 2017 PUCT Final Order allows for the Company to recover revenues associated with the relate back of rates to consumption on and after July 18, 2017, through a separate surcharge. New base rates, including additional surcharges associated with rate case expenses and the relate back of rates to consumption on and after July 18, 2017, through December 31, 2017, were implemented in January 2018. For financial reporting purposes, the Company deferred any recognition of the Company's request in its 2017 Texas Retail Rate Case until it received the 2017 PUCT Final Order on December 18, 2017. Accordingly, it reported in the fourth quarter of 2017 the cumulative effect of the 2017 PUCT Final Order, which related back to July 18, 2017. The 2017 PUCT Final Order required the Company to file a refund tariff if the federal statutory income tax rate, as it relates to the Company, were decreased before the Company files its next rate case. Following the enactment of the TCJA on December 22, 2017, and in compliance with the 2017 PUCT Final Order, on March 1, 2018, the Company filed with the PUCT and each of its municipalities a proposed refund tariff designed to reduce base charges for Texas customers equivalent to the expected annual decrease of $22.7 million in federal income tax expense resulting from the tax law changes. This filing was assigned PUCT Docket No. 48124. On March 27, 2018, the PUCT approved the Company's proposed refund tariff on an interim basis, subject to refund or surcharge, for customer billing effective April 1, 2018. Each of the Company's municipalities also implemented the Company's proposed tax credits on an interim basis effective April 1, 2018. The refund will be reflected in rates over a period of a year and will be updated annually until new base rates are implemented pursuant to the Company's next rate case filing. No party requested a hearing in the case before the PUCT by the deadline of April 16, 2018, and on April 18, 2018, the PUCT Staff filed its final recommendation supporting approval of the Company's application. The Company filed an agreed proposed order for final approval on behalf of all parties except the City of El Paso on April 30, 2018, and on May 31, 2018, the City of El Paso filed a notice with the PUCT stating that the City Council had authorized agreement with the proposed order. The refund tariff case is pending with the refund tariff subject to a final order from the PUCT. Energy Efficiency Cost Recovery Factor. On May 1, 2017, the Company filed its annual application, which was assigned PUCT Docket No. 47125, to establish its energy efficiency cost recovery factor for 2018. In addition to projected energy efficiency costs for 2018 and a reconciliation of collections to prior year actual costs, the Company requested approval of an incentive bonus for the 2016 energy efficiency program results in accordance with PUCT rules. Interim rates were approved effective January 1, 2018. The Company, the PUCT Staff and the City of El Paso reached an agreement that includes an incentive bonus of $0.8 million. The agreement was filed on January 25, 2018, and was approved by the PUCT on February 15, 2018. On May 1, 2018, the Company filed its annual application, which was assigned PUCT Docket No. 48332, to establish its energy efficiency cost recovery factor for 2019. In addition to projected energy efficiency costs for 2019 and a reconciliation to prior year actual costs, the Company requested approval of a $1.0 million incentive bonus for the 2017 energy efficiency program results in accordance with PUCT rules. Instead of convening an actual hearing on the merits of this case, the parties agreed to enter into the record the pre-filed testimony of the parties and certain other exhibits and then file briefs on the contested issues. The Company cannot predict the outcome of this matter at this time. Fuel and Purchased Power Costs. The Company's actual fuel costs, including purchased power energy costs, are recovered from customers through a fixed fuel factor. The PUCT has adopted the fuel cost recovery rule (the "Texas Fuel Rule") that allows the Company to seek periodic adjustments to its fixed fuel factor. The Company can seek to revise its fixed fuel factor based upon the approved formula at least four months after its last revision except in the month of December. The Texas Fuel Rule requires the Company to request to refund fuel costs in any month when the over-recovery balance exceeds a threshold material amount and it expects fuel costs to continue to be materially over-recovered. The Texas Fuel Rule also permits the Company to seek to surcharge fuel under-recoveries in any month the balance exceeds a threshold material amount and it expects fuel cost recovery to continue to be materially under-recovered. Fuel over and under-recoveries are considered material when they exceed 4% of the previous twelve months' fuel costs. All such fuel revenue and expense activities are subject to periodic final review by the PUCT in periodic fuel reconciliation proceedings. On November 30, 2016, the Company filed a request, which was assigned PUCT Docket No. 46610, to increase its fixed fuel factor by approximately 28.8% to reflect increased fuel expenses primarily related to an increase in the price of natural gas used to generate power. The increase in the fixed fuel factor was effective on an interim basis January 1, 2017, and approved by the PUCT on January 10, 2017. On October 13, 2017, the Company filed a request, which was assigned PUCT Docket No. 47692, to decrease the Texas fixed fuel factor by approximately 19% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. The decrease in the Texas fixed fuel factor became effective beginning with the November 2017 billing month. On April 13, 2018, the Company filed a request with the PUCT, which was assigned PUCT Docket No. 48264, to decrease the Texas fixed fuel factor by approximately 29% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. On April 25, 2018, the Company's proposed fuel factors were approved on an interim basis effective for the first billing cycle of the May 2018 billing month. The revised factor was approved by the PUCT and the docket closed on May 22, 2018. As of September 30, 2018, the Company had a net fuel over-recovery balance of approximately $6.9 million in Texas. On October 15, 2018, the Company filed a request with the PUCT, which was assigned PUCT Docket No. 48781, to decrease the Texas fixed fuel factor by approximately 6.99% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. On October 25, 2018, the Company's fixed fuel factor was approved on an interim basis effective for the first billing cycle of the November 2018 billing month. Once the final approval is received by the PUCT, the Texas fixed fuel factor will continue thereafter until changed by the PUCT. Fuel Reconciliation Proceeding. On September 27, 2016, the Company filed an application with the PUCT, designated as PUCT Docket No. 46308, to reconcile $436.6 million of Texas fuel and purchased power expenses incurred during the period of April 1, 2013, through March 31, 2016. On June 29, 2017, the PUCT approved a settlement in this proceeding. The settlement provides for the reconciliation of fuel and purchased power costs incurred from April 1, 2013, through March 31, 2016. Additionally, the settlement modifies and tightens the Palo Verde performance rewards measurement bands beginning with the 2018 performance period. The financial results for the nine and twelve-month periods ended September 30, 2017, include a $5.0 million, pre-tax increase to income reflecting the settlement of the Texas fuel reconciliation proceeding. This amount represents Palo Verde performance rewards associated with the 2013 to 2015 performance periods net of disallowed fuel and purchased power costs as approved in the settlement. The April 1, 2016, through September 30, 2018, Texas jurisdictional fuel and purchased power costs subject to prudence review total approximately $335.0 million. Community Solar. On June 8, 2015, the Company filed a petition with the PUCT to initiate a community solar program that includes the construction and ownership of a three-megawatt ("MW") solar photovoltaic system located at Montana Power Station ("MPS"). Participation is on a voluntary basis, and customers contract for a set capacity (kilowatt ("kW")) amount and receive all energy produced. This case was assigned PUCT Docket No. 44800. The Company filed a settlement agreement among all parties on July 1, 2016, approving the program, and the PUCT approved the settlement agreement and program on September 1, 2016. On April 19, 2017, the Company announced that the entire three-MW program was fully subscribed by approximately 1,500 Texas customers. The community solar facility began commercial operation on May 31, 2017. On March 20, 2018, the Company filed a petition with the PUCT and each of its regulatory authorities to expand its community solar program to include two-MW of solar powered generation from the ten-MW solar photovoltaic facility located at Newman Power Station ("Newman") and to reduce rates under the community solar tariff. The case before the PUCT was assigned PUCT Docket No. 48181 and is currently pending with hearings scheduled for December 4, 2018. The Company cannot predict the outcome of the case at this time. Other Required Approvals. The Company has obtained other required approvals for tariffs and other approvals required by the Texas Public Utility Regulatory Act and the PUCT. New Mexico Regulatory Matters 2015 New Mexico Rate Case Filing. On May 11, 2015, the Company filed a request with the NMPRC, in Case No. 15-00127-UT, for an annual increase in non-fuel base rates. On June 8, 2016, the NMPRC issued the NMPRC Final Order in Case No. 15-00127-UT (the "NMPRC Final Order"), which approved an annual increase in non-fuel base rates of approximately $0.6 million, an increase of approximately $0.5 million in other service fees and a decrease in the Company's allowed return on equity to 9.48%. The NMPRC Final Order concluded that all of the Company's new plant in service was reasonable and necessary and therefore would be recoverable in rates. The Company's rates were approved by the NMPRC effective July 1, 2016, and implemented at such time. Future New Mexico Rate Case Filing. On April 12, 2017, the NMPRC issued an order in Case No. 15-00109-UT requiring the Company to make a rate filing in New Mexico no later than July 31, 2019, using an appropriate historical test year period. New Mexico Order Commencing Review of the Effects of the TCJA on Regulated New Mexico Utilities. On January 24, 2018, the NMPRC initiated a proceeding in Case No. 18-00016-UT into the impact of the TCJA on New Mexico regulated utilities. On February 23, 2018, the Company responded to a NMPRC Staff inquiry regarding the proceeding. On April 4, 2018, the NMPRC issued an order requiring the Company to file a proposed interim rate rider to adjust the Company’s New Mexico base revenues in amounts equivalent to the Company’s reduced income tax expense for New Mexico customers resulting from the TCJA, to be implemented on or before May 1, 2018. The NMPRC order further requires that the Company record and track a regulatory liability for the excess accumulated deferred income taxes created by the change in the federal corporate income tax rate, consistent with the effective date of the TCJA, and subject to amortization determined by the NMPRC in the Company’s next general rate case. The Company recorded such a regulatory liability during the quarter ended December 31, 2017. On April 16, 2018, after consultation with the New Mexico Attorney General pursuant to the NMPRC order, the Company filed an interim rate rider with a proposed effective date of May 1, 2018. The annualized credits expected to be refunded to New Mexico customers approximate $4.9 million. The Company implemented the interim rate rider in customer bills beginning May 1, 2018 pursuant to the NMPRC order. On September 5, 2018, the NMPRC issued an order in Case No. 17-00255-UT involving Southwestern Public Service Company’s ("SPS’s") request to change rates in which the NMPRC directed SPS to refund the difference in corporate tax rate from January 1, 2018, through the effective date of new rates. SPS appealed the NMPRC order to the New Mexico Supreme Court in Southwestern Public Service Co. v. NMPRC, No. S-1-SC-37248, challenging the refund as prohibited retroactive ratemaking among other reasons. The Court issued a partial and interim stay of the rates on September 26, 2018. On September 12, 2018, the NMPRC in Case No. 18-00016-UT issued an Order Regarding the Disposition of Tax Savings Under the Federal Tax Cuts and Jobs Act of 2017 which put public utilities on notice that all revenue collected through general rates for the purpose of payment of federal income taxes is and will continue to be subject to possible refund upon a subsequent determination to be made in the appropriate pending or future Commission adjudicatory hearing. On October 11, 2018, SPS filed a Notice of Appeal of that NMPRC order to the New Mexico Supreme Court in Southwestern Public Service Co. v. NMPRC, No. S-1-SC-37308. A procedural schedule has not been issued in either case. In the event the NMPRC order in Case No. 17-00255-UT is upheld by the New Mexico Supreme Court, the Company would likely be required to record and refund approximately $1.2 million to its New Mexico customers, which represents tax benefits received by the Company for the period January 1, 2018, through April 30, 2018. The Company is monitoring the SPS cases and cannot determine the outcome of the cases at this time. Fuel and Purchased Power Costs. Historically, fuel and purchased power costs were recovered through base rates and a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC") that accounts for changes in the costs of fuel relative to the amount included in base rates. Effective July 1, 2016, with the implementation of the NMPRC Final Order, fuel and purchased power costs are no longer recovered through base rates but are recovered through the FPPCAC. The Company's request to reconcile its fuel and purchased power costs for the period January 1, 2013, through December 31, 2014, also was approved in the NMPRC Final Order. New Mexico jurisdictional costs subject to prudence review are costs from January 1, 2015, through September 30, 2018 that total approximately $200.1 million. At September 30, 2018, the Company had a net fuel over-recovery balance of approximately $2.9 million in New Mexico. As required, the Company filed a request to continue use of its FPPCAC with the NMPRC on January 5, 2018, which was assigned Case No. 18-00006-UT. Hearings in the case were held July 30 through August 6, 2018. The Company cannot predict the outcome of this case at this time. 5-MW Holloman Air Force Base ("HAFB") Facility Certificate of Convenience and Necessity ("CCN"). On October 7, 2015, in Case No. 15-00185-UT, the NMPRC issued a final order approving a CCN for a five-MW solar power generation facility located on HAFB in the Company's service territory in New Mexico. The Company and HAFB negotiated a retail contract, which includes a power sales agreement for the facility, to replace the existing load retention agreement that was approved by NMPRC final order issued October 5, 2016, in Case No. 16-00224-UT. The solar generation facility began commercial operation on October 18, 2018. New Mexico Efficient Use of Energy Recovery Factor. On July 1, 2016, the Company filed its annual application requesting approval of its 2017 Energy Efficiency and Load Management Plan and to establish energy efficiency cost recovery factors for 2017. In addition to projected energy efficiency costs for 2017, the Company requested approval of a $0.4 million incentive for 2017 energy efficiency programs in accordance with NMPRC rules. This application was assigned Case No. 16-00185-UT. On February 22, 2017, the NMPRC issued a final order approving the Company’s 2017 Energy Efficiency and Load Management Plan and authorizing recovery in 2017 of a base incentive of $0.4 million. The Company’s energy efficiency cost recovery factors were approved and effective in customer bills beginning on March 1, 2017. NMPRC rules authorize continuation of the energy efficiency programs and incentive approved in Case No. 16-00185-UT through 2018. On July 1, 2016, the Company filed its 2015 Annual Report for Energy Efficiency Programs, which included an incentive for verified 2015 program performance of $0.3 million, which was approved in Case No. 13-00176-UT. The Company recorded the $0.3 million approved incentive in operating revenues in the first quarter of 2017. In addition, on June 30, 2017, the Company filed its 2016 Annual Report for Energy Efficiency Programs, which included an incentive for verified 2016 program performance of $0.4 million that was approved in Case No. 13-00176-UT. The Company recorded the $0.4 million approved incentive in operating revenues in the third quarter of 2017. On July 2, 2018, the Company filed its required application for approval of its 2019-2021 Energy Efficiency and Load Management Plan and cost recovery factor. The application includes a request for a base incentive of 7.1% of program expenditures, or approximately $0.4 million annually for 2019-2021. The application was assigned Case No. 18-00116-UT and is currently pending with hearings scheduled for November 7, 2018. The Company cannot predict the outcome of this case at this time. Community Solar. On April 24, 2018, the Company filed an application with the NMPRC to initiate a community solar program to include construction and ownership of a two-MW solar photovoltaic system located in Doña Ana County near the City of Las Cruces. Customer participation will be on a voluntary basis, and customers will contract for a set capacity (kW) amount and receive all energy produced by their subscribed capacity. The application was assigned Case No. 18-00099-UT and was dismissed without prejudice on October 31, 2018. Integrated Resource Plan. On September 17, 2018, the Company filed its Integrated Resource Plan for the period 2018-2037 with the NMPRC in Case No. 18-00293-UT as required by regulation and the Joint Stipulation in NMPRC Case No. 15-00241-UT, which was the Company’s prior integrated resource plan filing. The triennial filing requires a public advisory process as part of the development of the plan to identify a cost-effective portfolio of resources. The filed plan is subject to written public comments filed with the NMPRC to which the Company responded on October 29, 2018. The Utility Division Staff of the NMPRC is required to file a written recommendation on or about November 16, 2018, as to whether the NMPRC should accept the proposed plan as filed. The NMPRC may accept the plan as compliant with regulation or determine that the plan is not compliant and return it to the Company with instructions for re-filing. The Company cannot predict the outcome of the NMPRC’s review of the plan or the outcome of this case at this time. Issuance of Long-Term Debt, Securities Financing, and Guarantee of Debt. On October 7, 2015, the Company received approval in NMPRC Case No. 15-00280-UT to guarantee the issuance of up to $65.0 million of long-term debt by the Rio Grande Resources Trust II (the "RGRT") to finance future purchases of nuclear fuel and to refinance existing nuclear fuel debt obligations, which remains effective. Under this authorization, on June 28, 2018, the RGRT completed the sale of $65.0 million in aggregate principal amount of 4.07% Senior Guaranteed Notes due August 15, 2025, as further described below (the "RGRT Notes"). On October 4, 2017, the Company received additional approval in NMPRC Case No. 17-00217-UT to amend and extend the Company's Revolving Credit Facility (the "RCF"), issue up to $350.0 million in long-term debt and to redeem and refinance the $63.5 million 2009 Series A 7.25% Pollution Control Bonds and the $37.1 million 2009 Series B 7.25% Pollution Control Bonds, which have optional redemptions beginning in 2019. The NMPRC approval to issue $350.0 million in long-term debt supersedes its prior approval. Under this authorization, on June 28, 2018, the Company issued $125.0 million in aggregate principal amount of the Company's 4.22% Senior Notes due August 15, 2028. Additionally, on September 13, 2018, the Company and the Bank of New York Mellon Trust Company, N.A., as trustee of the RGRT, entered into a $350.0 million third amended and restated credit agreement. See Note L, Long-Term Debt and Financing Obligations. Other Required Approvals. The Company has obtained other required approvals for tariffs and other approvals as required by the New Mexico Public Utility Act and the NMPRC. Federal Regulatory Matters Inquiry Regarding the Effect of the TCJA on Commission-Jurisdictional Rates and Order to Show Cause. On March 15, 2018, the FERC issued two show cause orders under Section 206 of the Federal Power Act and Rule 209(a) of the FERC’s Rules of Practice and Procedure, directing 48 individual public utilities with stated transmission rates or transmission formula rates with a fixed line item of 35% for the federal income tax component to, within 60 days of the date of the orders, either (1) propose revisions to their transmission rates under their open access transmission tariffs or transmission owner tariffs on file with the FERC, or (2) show cause why they should not be required to do so. The Company was included in the list of public utilities impacted by the FERC orders. On May 14, 2018, the Company submitted its response, as required by the FERC order, which demonstrated that the reduced annual income tax does not cause the Company's total transmission revenues to become excessive and therefore no rate reduction was justified. Instead, the Company stated in its response that it will make preparations for a future filing in which it will seek approval for revised Open Access Transmission Tariff ("OATT") rates that would include the recovery of an increased total transmission revenue requirement from OATT customers based on current circumstances and appropriate forward-looking adjustments. The Company expects to file its request for this approval in the third quarter of 2019. The Company cannot predict the outcome of this matter at this time. Issuance of Long-Term Debt, Securities Financing, and Guarantee of Debt. On October 31, 2017, the FERC issued an order in Docket No. ES17-54-000 approving the Company’s filing to (i) amend and extend the RCF; (ii) issue up to $350.0 million in long-term debt; (iii) guarantee the issuance of up to $65.0 million of long-term debt by the RGRT; and (iv) redeem and refinance the $63.5 million 2009 Series A 7.25% Pollution Control Bonds and the $37.1 million 2009 Series B 7.25% Pollution Control Bonds, which have optional redemptions beginning in 2019. The order also approved the Company's request to continue to utilize the Company's existing RCF with the ability to amend and extend at a future date. The authorization is effective from November 15, 2017, through November 14, 2019, and supersedes prior FERC approvals. Under this authorization, on June 28, 2018, the Company issued $125.0 million in aggregate principal amount of the Company's 4.22% Senior Notes due August 15, 2028, and the RGRT completed the sale of $65.0 million in aggregate principal amount of its 4.07% Senior Guaranteed Notes due August 15, 2025. Additionally, on September 13, 2018, the Company and the Bank of New York Mellon Trust Company, N.A., as trustee of the RGRT, entered into a $350.0 million third amended and restated credit agreement. See Note L, Long-Term Debt and Financing Obligations. Other Required Approvals. The Company has obtained required approvals for rates, tariffs and other approvals as required by the FERC.

Regulation

General

The rates and services of the Company are regulated by incorporated municipalities in Texas, the PUCT, the NMPRC and the FERC. Municipal orders, ordinances and other agreements regarding rates and services adopted by Texas municipalities are subject to review and approval by the PUCT. The FERC has jurisdiction over the Company's wholesale (sales for resale - full requirement customer) transactions, transmission service and compliance with federally-mandated reliability standards. The decisions of the PUCT, the NMPRC and the FERC are subject to judicial review.

Texas Regulatory Matters

2015 Texas Retail Rate Case Filing. On August 10, 2015, the Company filed with the City of El Paso, other municipalities incorporated in its Texas service territory, and the PUCT in Docket No. 44941, a request for an annual increase in non-fuel base revenues ("2015 Texas Retail Rate Case"). On July 21, 2016, the parties to PUCT Docket No. 44941 filed the Joint Motion to Implement Uncontested Amended and Restated Stipulation and Agreement which was unopposed by the parties. On August 25, 2016, the PUCT issued the PUCT Final Order in Docket No. 44941 ("2016 PUCT Final Order"). Interim rates associated with the annual non-fuel base rate increase became effective on April 1, 2016. The additional surcharges associated with the incremental Four Corners Generating Station ("Four Corners") costs, rate case expenses and the relate back of rates to consumption on and after January 12, 2016, through March 31, 2016, were implemented on October 1, 2016.

For financial reporting purposes, the Company deferred any recognition of the Company's request in its 2015 Texas Retail Rate Case until it received the 2016 PUCT Final Order on August 25, 2016. Accordingly, it reported in the third quarter of 2016 the cumulative effect of the 2016 PUCT Final Order, which related back to January 12, 2016.

2017 Texas Retail Rate Case Filing. On February 13, 2017, the Company filed with the City of El Paso, other municipalities incorporated in the Company's Texas service territory and the PUCT in Docket No. 46831, a request for an increase in non-fuel base revenues ("2017 Texas Retail Rate Case"). On November 2, 2017, the Company filed the Joint Motion to Implement Uncontested Stipulation and Agreement with the Administrative Law Judges for the 2017 Texas Retail Rate Case.

On December 18, 2017, the PUCT issued the PUCT Final Order in Docket No. 46831 ("2017 PUCT Final Order"), which provides, among other things, for the following: (i) an annual non-fuel base rate increase of $14.5 million; (ii) a return on equity of 9.65%; (iii) all new plant in service as filed in the Company's rate filing package was prudent and used and useful and therefore is included in rate base; (iv) recovery of the costs of decommissioning Four Corners in the amount of $5.5 million over a seven year period beginning August 1, 2017; (v) the Company to recover reasonable rate case expenses of approximately $3.4 million through a separate surcharge over a three year period; and (vi) a requirement that the Company file a refund tariff if the federal statutory income tax rate, as it relates to the Company, is decreased before the Company files its next rate case. The 2017 PUCT Final Order also established baseline revenue requirements for recovery of future transmission and distribution investment costs (for which the Company may seek recovery after January 1, 2019, and for which the Company anticipates requesting recovery in the first quarter of 2019) and includes a minimum monthly bill of $30.00 for new residential customers with distributed generation, such as private rooftop solar. Additionally, the 2017 PUCT Final Order allows for the annual recovery of $2.1 million of nuclear decommissioning funding and establishes annual depreciation expense that is approximately $1.9 million lower than the annual amount requested by the Company in its initial filing. Finally, the 2017 PUCT Final Order allows for the Company to recover revenues associated with the relate back of rates to consumption on and after July 18, 2017, through a separate surcharge.

New base rates, including additional surcharges associated with rate case expenses and the relate back of rates to consumption on and after July 18, 2017, through December 31, 2017, were implemented in January 2018.

For financial reporting purposes, the Company deferred any recognition of the Company's request in its 2017 Texas Retail Rate Case until it received the 2017 PUCT Final Order on December 18, 2017. Accordingly, it reported in the fourth quarter of 2017 the cumulative effect of the 2017 PUCT Final Order, which related back to July 18, 2017.

The 2017 PUCT Final Order required the Company to file a refund tariff if the federal statutory income tax rate, as it relates to the Company, were decreased before the Company files its next rate case. Following the enactment of the TCJA on December 22, 2017, and in compliance with the 2017 PUCT Final Order, on March 1, 2018, the Company filed with the PUCT and each of its municipalities a proposed refund tariff designed to reduce base charges for Texas customers equivalent to the expected annual decrease of $22.7 million in federal income tax expense resulting from the tax law changes. This filing was assigned PUCT Docket No. 48124. On March 27, 2018, the PUCT approved the Company's proposed refund tariff on an interim basis, subject to refund or surcharge, for customer billing effective April 1, 2018. Each of the Company's municipalities also implemented the Company's proposed tax credits on an interim basis effective April 1, 2018. The refund will be reflected in rates over a period of a year and will be updated annually until new base rates are implemented pursuant to the Company's next rate case filing. No party requested a hearing in the case before the PUCT by the deadline of April 16, 2018, and on April 18, 2018, the PUCT Staff filed its final recommendation supporting approval of the Company's application. The Company filed an agreed proposed order for final approval on behalf of all parties except the City of El Paso on April 30, 2018, and on May 31, 2018, the City of El Paso filed a notice with the PUCT stating that the City Council had authorized agreement with the proposed order. The refund tariff case is pending with the refund tariff subject to a final order from the PUCT.

Energy Efficiency Cost Recovery Factor. On May 1, 2017, the Company filed its annual application, which was assigned PUCT Docket No. 47125, to establish its energy efficiency cost recovery factor for 2018. In addition to projected energy efficiency costs for 2018 and a reconciliation of collections to prior year actual costs, the Company requested approval of an incentive bonus for the 2016 energy efficiency program results in accordance with PUCT rules. Interim rates were approved effective January 1, 2018. The Company, the PUCT Staff and the City of El Paso reached an agreement that includes an incentive bonus of $0.8 million. The agreement was filed on January 25, 2018, and was approved by the PUCT on February 15, 2018.

On May 1, 2018, the Company filed its annual application, which was assigned PUCT Docket No. 48332, to establish its energy efficiency cost recovery factor for 2019. In addition to projected energy efficiency costs for 2019 and a reconciliation to prior year actual costs, the Company requested approval of a $1.0 million incentive bonus for the 2017 energy efficiency program results in accordance with PUCT rules. Instead of convening an actual hearing on the merits of this case, the parties agreed to enter into the record the pre-filed testimony of the parties and certain other exhibits and then file briefs on the contested issues. The Company cannot predict the outcome of this matter at this time.

Fuel and Purchased Power Costs. The Company's actual fuel costs, including purchased power energy costs, are recovered from customers through a fixed fuel factor. The PUCT has adopted the fuel cost recovery rule (the "Texas Fuel Rule") that allows the Company to seek periodic adjustments to its fixed fuel factor. The Company can seek to revise its fixed fuel factor based upon the approved formula at least four months after its last revision except in the month of December. The Texas Fuel Rule requires the Company to request to refund fuel costs in any month when the over-recovery balance exceeds a threshold material amount and it expects fuel costs to continue to be materially over-recovered. The Texas Fuel Rule also permits the Company to seek to surcharge fuel under-recoveries in any month the balance exceeds a threshold material amount and it expects fuel cost recovery to continue to be materially under-recovered. Fuel over and under-recoveries are considered material when they exceed 4% of the previous twelve months' fuel costs. All such fuel revenue and expense activities are subject to periodic final review by the PUCT in periodic fuel reconciliation proceedings.

On November 30, 2016, the Company filed a request, which was assigned PUCT Docket No. 46610, to increase its fixed fuel factor by approximately 28.8% to reflect increased fuel expenses primarily related to an increase in the price of natural gas used to generate power. The increase in the fixed fuel factor was effective on an interim basis January 1, 2017, and approved by the PUCT on January 10, 2017.

On October 13, 2017, the Company filed a request, which was assigned PUCT Docket No. 47692, to decrease the Texas fixed fuel factor by approximately 19% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. The decrease in the Texas fixed fuel factor became effective beginning with the November 2017 billing month.

On April 13, 2018, the Company filed a request with the PUCT, which was assigned PUCT Docket No. 48264, to decrease the Texas fixed fuel factor by approximately 29% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. On April 25, 2018, the Company's proposed fuel factors were approved on an interim basis effective for the first billing cycle of the May 2018 billing month. The revised factor was approved by the PUCT and the docket closed on May 22, 2018. As of September 30, 2018, the Company had a net fuel over-recovery balance of approximately $6.9 million in Texas.

On October 15, 2018, the Company filed a request with the PUCT, which was assigned PUCT Docket No. 48781, to decrease the Texas fixed fuel factor by approximately 6.99% to reflect decreased fuel expenses primarily related to a decrease in the price of natural gas used to generate power. On October 25, 2018, the Company's fixed fuel factor was approved on an interim basis effective for the first billing cycle of the November 2018 billing month. Once the final approval is received by the PUCT, the Texas fixed fuel factor will continue thereafter until changed by the PUCT.

Fuel Reconciliation Proceeding. On September 27, 2016, the Company filed an application with the PUCT, designated as PUCT Docket No. 46308, to reconcile $436.6 million of Texas fuel and purchased power expenses incurred during the period of April 1, 2013, through March 31, 2016. On June 29, 2017, the PUCT approved a settlement in this proceeding. The settlement provides for the reconciliation of fuel and purchased power costs incurred from April 1, 2013, through March 31, 2016. Additionally, the settlement modifies and tightens the Palo Verde performance rewards measurement bands beginning with the 2018 performance period. The financial results for the nine and twelve-month periods ended September 30, 2017, include a $5.0 million, pre-tax increase to income reflecting the settlement of the Texas fuel reconciliation proceeding. This amount represents Palo Verde performance rewards associated with the 2013 to 2015 performance periods net of disallowed fuel and purchased power costs as approved in the settlement. The April 1, 2016, through September 30, 2018, Texas jurisdictional fuel and purchased power costs subject to prudence review total approximately $335.0 million.

Community Solar. On June 8, 2015, the Company filed a petition with the PUCT to initiate a community solar program that includes the construction and ownership of a three-megawatt ("MW") solar photovoltaic system located at Montana Power Station ("MPS"). Participation is on a voluntary basis, and customers contract for a set capacity (kilowatt ("kW")) amount and receive all energy produced. This case was assigned PUCT Docket No. 44800. The Company filed a settlement agreement among all parties on July 1, 2016, approving the program, and the PUCT approved the settlement agreement and program on September 1, 2016. On April 19, 2017, the Company announced that the entire three-MW program was fully subscribed by approximately 1,500 Texas customers. The community solar facility began commercial operation on May 31, 2017.

On March 20, 2018, the Company filed a petition with the PUCT and each of its regulatory authorities to expand its community solar program to include two-MW of solar powered generation from the ten-MW solar photovoltaic facility located at Newman Power Station ("Newman") and to reduce rates under the community solar tariff. The case before the PUCT was assigned PUCT Docket No. 48181 and is currently pending with hearings scheduled for December 4, 2018. The Company cannot predict the outcome of the case at this time.

Other Required Approvals. The Company has obtained other required approvals for tariffs and other approvals required by the Texas Public Utility Regulatory Act and the PUCT.

New Mexico Regulatory Matters

2015 New Mexico Rate Case Filing. On May 11, 2015, the Company filed a request with the NMPRC, in Case No. 15-00127-UT, for an annual increase in non-fuel base rates. On June 8, 2016, the NMPRC issued the NMPRC Final Order in Case No. 15-00127-UT (the "NMPRC Final Order"), which approved an annual increase in non-fuel base rates of approximately $0.6 million, an increase of approximately $0.5 million in other service fees and a decrease in the Company's allowed return on equity to 9.48%. The NMPRC Final Order concluded that all of the Company's new plant in service was reasonable and necessary and therefore would be recoverable in rates. The Company's rates were approved by the NMPRC effective July 1, 2016, and implemented at such time.

Future New Mexico Rate Case Filing. On April 12, 2017, the NMPRC issued an order in Case No. 15-00109-UT requiring the Company to make a rate filing in New Mexico no later than July 31, 2019, using an appropriate historical test year period.

New Mexico Order Commencing Review of the Effects of the TCJA on Regulated New Mexico Utilities. On January 24, 2018, the NMPRC initiated a proceeding in Case No. 18-00016-UT into the impact of the TCJA on New Mexico regulated utilities. On February 23, 2018, the Company responded to a NMPRC Staff inquiry regarding the proceeding. On April 4, 2018, the NMPRC issued an order requiring the Company to file a proposed interim rate rider to adjust the Company’s New Mexico base revenues in amounts equivalent to the Company’s reduced income tax expense for New Mexico customers resulting from the TCJA, to be implemented on or before May 1, 2018. The NMPRC order further requires that the Company record and track a regulatory liability for the excess accumulated deferred income taxes created by the change in the federal corporate income tax rate, consistent with the effective date of the TCJA, and subject to amortization determined by the NMPRC in the Company’s next general rate case. The Company recorded such a regulatory liability during the quarter ended December 31, 2017. On April 16, 2018, after consultation with the New Mexico Attorney General pursuant to the NMPRC order, the Company filed an interim rate rider with a proposed effective date of May 1, 2018. The annualized credits expected to be refunded to New Mexico customers approximate $4.9 million. The Company implemented the interim rate rider in customer bills beginning May 1, 2018 pursuant to the NMPRC order.

On September 5, 2018, the NMPRC issued an order in Case No. 17-00255-UT involving Southwestern Public Service Company’s ("SPS’s") request to change rates in which the NMPRC directed SPS to refund the difference in corporate tax rate from January 1, 2018, through the effective date of new rates. SPS appealed the NMPRC order to the New Mexico Supreme Court in Southwestern Public Service Co. v. NMPRC, No. S-1-SC-37248, challenging the refund as prohibited retroactive ratemaking among other reasons. The Court issued a partial and interim stay of the rates on September 26, 2018. On September 12, 2018, the NMPRC in Case No. 18-00016-UT issued an Order Regarding the Disposition of Tax Savings Under the Federal Tax Cuts and Jobs Act of 2017 which put public utilities on notice that all revenue collected through general rates for the purpose of payment of federal income taxes is and will continue to be subject to possible refund upon a subsequent determination to be made in the appropriate pending or future Commission adjudicatory hearing. On October 11, 2018, SPS filed a Notice of Appeal of that NMPRC order to the New Mexico Supreme Court in Southwestern Public Service Co. v. NMPRC, No. S-1-SC-37308. A procedural schedule has not been issued in either case. In the event the NMPRC order in Case No. 17-00255-UT is upheld by the New Mexico Supreme Court, the Company would likely be required to record and refund approximately $1.2 million to its New Mexico customers, which represents tax benefits received by the Company for the period January 1, 2018, through April 30, 2018. The Company is monitoring the SPS cases and cannot determine the outcome of the cases at this time.

Fuel and Purchased Power Costs. Historically, fuel and purchased power costs were recovered through base rates and a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC") that accounts for changes in the costs of fuel relative to the amount included in base rates. Effective July 1, 2016, with the implementation of the NMPRC Final Order, fuel and purchased power costs are no longer recovered through base rates but are recovered through the FPPCAC. The Company's request to reconcile its fuel and purchased power costs for the period January 1, 2013, through December 31, 2014, also was approved in the NMPRC Final Order. New Mexico jurisdictional costs subject to prudence review are costs from January 1, 2015, through September 30, 2018 that total approximately $200.1 million. At September 30, 2018, the Company had a net fuel over-recovery balance of approximately $2.9 million in New Mexico. As required, the Company filed a request to continue use of its FPPCAC with the NMPRC on January 5, 2018, which was assigned Case No. 18-00006-UT. Hearings in the case were held July 30 through August 6, 2018. The Company cannot predict the outcome of this case at this time.

5-MW Holloman Air Force Base ("HAFB") Facility Certificate of Convenience and Necessity ("CCN"). On October 7, 2015, in Case No. 15-00185-UT, the NMPRC issued a final order approving a CCN for a five-MW solar power generation facility located on HAFB in the Company's service territory in New Mexico. The Company and HAFB negotiated a retail contract, which includes a power sales agreement for the facility, to replace the existing load retention agreement that was approved by NMPRC final order issued October 5, 2016, in Case No. 16-00224-UT. The solar generation facility began commercial operation on October 18, 2018.

New Mexico Efficient Use of Energy Recovery Factor. On July 1, 2016, the Company filed its annual application requesting approval of its 2017 Energy Efficiency and Load Management Plan and to establish energy efficiency cost recovery factors for 2017. In addition to projected energy efficiency costs for 2017, the Company requested approval of a $0.4 million incentive for 2017 energy efficiency programs in accordance with NMPRC rules. This application was assigned Case No. 16-00185-UT. On February 22, 2017, the NMPRC issued a final order approving the Company’s 2017 Energy Efficiency and Load Management Plan and authorizing recovery in 2017 of a base incentive of $0.4 million. The Company’s energy efficiency cost recovery factors were approved and effective in customer bills beginning on March 1, 2017. NMPRC rules authorize continuation of the energy efficiency programs and incentive approved in Case No. 16-00185-UT through 2018.

On July 1, 2016, the Company filed its 2015 Annual Report for Energy Efficiency Programs, which included an incentive for verified 2015 program performance of $0.3 million, which was approved in Case No. 13-00176-UT. The Company recorded the $0.3 million approved incentive in operating revenues in the first quarter of 2017. In addition, on June 30, 2017, the Company filed its 2016 Annual Report for Energy Efficiency Programs, which included an incentive for verified 2016 program performance of $0.4 million that was approved in Case No. 13-00176-UT. The Company recorded the $0.4 million approved incentive in operating revenues in the third quarter of 2017.

On July 2, 2018, the Company filed its required application for approval of its 2019-2021 Energy Efficiency and Load Management Plan and cost recovery factor. The application includes a request for a base incentive of 7.1% of program expenditures, or approximately $0.4 million annually for 2019-2021. The application was assigned Case No. 18-00116-UT and is currently pending with hearings scheduled for November 7, 2018. The Company cannot predict the outcome of this case at this time.

Community Solar. On April 24, 2018, the Company filed an application with the NMPRC to initiate a community solar program to include construction and ownership of a two-MW solar photovoltaic system located in Doña Ana County near the City of Las Cruces. Customer participation will be on a voluntary basis, and customers will contract for a set capacity (kW) amount and receive all energy produced by their subscribed capacity. The application was assigned Case No. 18-00099-UT and was dismissed without prejudice on October 31, 2018.

Integrated Resource Plan. On September 17, 2018, the Company filed its Integrated Resource Plan for the period 2018-2037 with the NMPRC in Case No. 18-00293-UT as required by regulation and the Joint Stipulation in NMPRC Case No. 15-00241-UT, which was the Company’s prior integrated resource plan filing. The triennial filing requires a public advisory process as part of the development of the plan to identify a cost-effective portfolio of resources. The filed plan is subject to written public comments filed with the NMPRC to which the Company responded on October 29, 2018. The Utility Division Staff of the NMPRC is required to file a written recommendation on or about November 16, 2018, as to whether the NMPRC should accept the proposed plan as filed. The NMPRC may accept the plan as compliant with regulation or determine that the plan is not compliant and return it to the Company with instructions for re-filing. The Company cannot predict the outcome of the NMPRC’s review of the plan or the outcome of this case at this time.

Issuance of Long-Term Debt, Securities Financing, and Guarantee of Debt. On October 7, 2015, the Company received approval in NMPRC Case No. 15-00280-UT to guarantee the issuance of up to $65.0 million of long-term debt by the Rio Grande Resources Trust II (the "RGRT") to finance future purchases of nuclear fuel and to refinance existing nuclear fuel debt obligations, which remains effective. Under this authorization, on June 28, 2018, the RGRT completed the sale of $65.0 million in aggregate principal amount of 4.07% Senior Guaranteed Notes due August 15, 2025, as further described below (the "RGRT Notes"). On October 4, 2017, the Company received additional approval in NMPRC Case No. 17-00217-UT to amend and extend the Company's Revolving Credit Facility (the "RCF"), issue up to $350.0 million in long-term debt and to redeem and refinance the $63.5 million 2009 Series A 7.25% Pollution Control Bonds and the $37.1 million 2009 Series B 7.25% Pollution Control Bonds, which have optional redemptions beginning in 2019. The NMPRC approval to issue $350.0 million in long-term debt supersedes its prior approval. Under this authorization, on June 28, 2018, the Company issued $125.0 million in aggregate principal amount of the Company's 4.22% Senior Notes due August 15, 2028. Additionally, on September 13, 2018, the Company and the Bank of New York Mellon Trust Company, N.A., as trustee of the RGRT, entered into a $350.0 million third amended and restated credit agreement. See Note L, Long-Term Debt and Financing Obligations.

Other Required Approvals. The Company has obtained other required approvals for tariffs and other approvals as required by the New Mexico Public Utility Act and the NMPRC.

Federal Regulatory Matters

Inquiry Regarding the Effect of the TCJA on Commission-Jurisdictional Rates and Order to Show Cause. On March 15, 2018, the FERC issued two show cause orders under Section 206 of the Federal Power Act and Rule 209(a) of the FERC’s Rules of Practice and Procedure, directing 48 individual public utilities with stated transmission rates or transmission formula rates with a fixed line item of 35% for the federal income tax component to, within 60 days of the date of the orders, either (1) propose revisions to their transmission rates under their open access transmission tariffs or transmission owner tariffs on file with the FERC, or (2) show cause why they should not be required to do so. The Company was included in the list of public utilities impacted by the FERC orders. On May 14, 2018, the Company submitted its response, as required by the FERC order, which demonstrated that the reduced annual income tax does not cause the Company's total transmission revenues to become excessive and therefore no rate reduction was justified. Instead, the Company stated in its response that it will make preparations for a future filing in which it will seek approval for revised Open Access Transmission Tariff ("OATT") rates that would include the recovery of an increased total transmission revenue requirement from OATT customers based on current circumstances and appropriate forward-looking adjustments. The Company expects to file its request for this approval in the third quarter of 2019. The Company cannot predict the outcome of this matter at this time.

Issuance of Long-Term Debt, Securities Financing, and Guarantee of Debt. On October 31, 2017, the FERC issued an order in Docket No. ES17-54-000 approving the Company’s filing to (i) amend and extend the RCF; (ii) issue up to $350.0 million in long-term debt; (iii) guarantee the issuance of up to $65.0 million of long-term debt by the RGRT; and (iv) redeem and refinance the $63.5 million 2009 Series A 7.25% Pollution Control Bonds and the $37.1 million 2009 Series B 7.25% Pollution Control Bonds, which have optional redemptions beginning in 2019. The order also approved the Company's request to continue to utilize the Company's existing RCF with the ability to amend and extend at a future date. The authorization is effective from November 15, 2017, through November 14, 2019, and supersedes prior FERC approvals. Under this authorization, on June 28, 2018, the Company issued $125.0 million in aggregate principal amount of the Company's 4.22% Senior Notes due August 15, 2028, and the RGRT completed the sale of $65.0 million in aggregate principal amount of its 4.07% Senior Guaranteed Notes due August 15, 2025. Additionally, on September 13, 2018, the Company and the Bank of New York Mellon Trust Company, N.A., as trustee of the RGRT, entered into a $350.0 million third amended and restated credit agreement. See Note L, Long-Term Debt and Financing Obligations.

Other Required Approvals. The Company has obtained required approvals for rates, tariffs and other approvals as required by the FERC.