Regulation	3 Months Ended
Mar. 31, 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) 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"). The 2016 PUCT Final Order provided for: (i) an annual non-fuel base rate increase, lower annual depreciation expense, a revised return on equity for allowance for funds used during construction ("AFUDC") purposes, and the inclusion of substantially all new plant in service in rate base; (ii) an additional annual non-fuel base rate increase of $3.7 million related to Four Corners Generating Station ("Four Corners") costs, which was collected through a surcharge that terminated on July 11, 2017; (iii) removing the separate rate treatment for residential customers with solar systems that the Company had proposed in its August 10, 2015 filing; (iv) allowing the Company to recover $3.1 million in rate case expenses through a separate surcharge; and (v) allowing the Company to recover revenues associated with the relate back of rates to consumption on and after January 12, 2016 through March 31, 2016 through a separate surcharge. 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 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 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 refund tariff case is pending with the refund tariff subject to final action by the incorporated municipalities in the Company's Texas service territory and 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 $1.1 million incentive bonus for the 2017 energy efficiency program results in accordance with PUCT rules. 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 ("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 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. If no party to the case requests a hearing by May 14, 2018, the Company's fuel factors will become final as provided by the PUCT's rules and no further action by the PUCT is required. The Texas fixed fuel factor will continue thereafter until changed by the PUCT. As of March 31, 2018, the Company had a net fuel over-recovery balance of approximately $13.3 million in Texas. 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 twelve months ended March 31, 2018 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. Texas jurisdictional fuel and purchased power costs subject to prudence review are costs from April 1, 2016 through March 31, 2018, that total approximately $271.3 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 3 Megawatts ("MW") solar photovoltaic system located at Montana Power Station ("MPS"). Participation is on a voluntary basis, and customers contract for a set capacity (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 3 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 2 MW of solar powered generation from the 10 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 Docket No. 48181 and is currently pending. 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 ("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. On April 25, 2018, the NMPRC approved the Company's interim rate rider to be implemented in customer bills beginning May 1, 2018. 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 ("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 Case No. 15-00127-UT. New Mexico jurisdictional costs subject to prudence review are costs from January 1, 2015 through March 31, 2018 that total approximately $181.0 million. At March 31, 2018, the Company had a net fuel over-recovery balance of approximately $0.9 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 NMPRC Case No. 18-00006-UT. Hearings in the case are scheduled to begin in July 2018. 5 MW Holloman Air Force Base ("HAFB") Facility Certificate of Convenience and Necessity ("CCN"). On October 7, 2015, in NMPRC Case No. 15-00185-UT, the NMPRC issued a final order approving a CCN for a 5 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 which was approved by final order issued October 5, 2016 in NMPRC Case No. 16-00224-UT. Construction of the solar generation facility is expected to be completed in the third quarter of 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 case 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. 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. Community Solar. On April 24, 2018, the Company filed a petition with the NMPRC to initiate a community solar program to include construction and ownership of a 2 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 Company cannot predict the outcome of this petition at this time. 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 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 is included in the list of public utilities impacted by the FERC orders and is currently evaluating a response to the orders. 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) 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"). The 2016 PUCT Final Order provided for: (i) an annual non-fuel base rate increase, lower annual depreciation expense, a revised return on equity for allowance for funds used during construction ("AFUDC") purposes, and the inclusion of substantially all new plant in service in rate base; (ii) an additional annual non-fuel base rate increase of $3.7 million related to Four Corners Generating Station ("Four Corners") costs, which was collected through a surcharge that terminated on July 11, 2017; (iii) removing the separate rate treatment for residential customers with solar systems that the Company had proposed in its August 10, 2015 filing; (iv) allowing the Company to recover $3.1 million in rate case expenses through a separate surcharge; and (v) allowing the Company to recover revenues associated with the relate back of rates to consumption on and after January 12, 2016 through March 31, 2016 through a separate surcharge.

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 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 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 refund tariff case is pending with the refund tariff subject to final action by the incorporated municipalities in the Company's Texas service territory and 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 $1.1 million incentive bonus for the 2017 energy efficiency program results in accordance with PUCT rules.

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 ("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 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. If no party to the case requests a hearing by May 14, 2018, the Company's fuel factors will become final as provided by the PUCT's rules and no further action by the PUCT is required. The Texas fixed fuel factor will continue thereafter until changed by the PUCT. As of March 31, 2018, the Company had a net fuel over-recovery balance of approximately $13.3 million in Texas.

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 twelve months ended March 31, 2018 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. Texas jurisdictional fuel and purchased power costs subject to prudence review are costs from April 1, 2016 through March 31, 2018, that total approximately $271.3 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 3 Megawatts ("MW") solar photovoltaic system located at Montana Power Station ("MPS"). Participation is on a voluntary basis, and customers contract for a set capacity (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 3 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 2 MW of solar powered generation from the 10 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 Docket No. 48181 and is currently pending.

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 ("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. On April 25, 2018, the NMPRC approved the Company's interim rate rider to be implemented in customer bills beginning May 1, 2018.

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 ("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 Case No. 15-00127-UT. New Mexico jurisdictional costs subject to prudence review are costs from January 1, 2015 through March 31, 2018 that total approximately $181.0 million. At March 31, 2018, the Company had a net fuel over-recovery balance of approximately $0.9 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 NMPRC Case No. 18-00006-UT. Hearings in the case are scheduled to begin in July 2018.

5 MW Holloman Air Force Base ("HAFB") Facility Certificate of Convenience and Necessity ("CCN"). On October 7, 2015, in NMPRC Case No. 15-00185-UT, the NMPRC issued a final order approving a CCN for a 5 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 which was approved by final order issued October 5, 2016 in NMPRC Case No. 16-00224-UT. Construction of the solar generation facility is expected to be completed in the third quarter of 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 case 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.

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.

Community Solar. On April 24, 2018, the Company filed a petition with the NMPRC to initiate a community solar program to include construction and ownership of a 2 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 Company cannot predict the outcome of this petition at this time.

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 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 is included in the list of public utilities impacted by the FERC orders and is currently evaluating a response to the orders.

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