Table of Contents Retail non-fuel base revenues . For the twelve months ended December 31, 2019, retail non-fuel base revenues increased $9.6 million, or 1.5%, compared to the twelve months ended December 31, 2018. Retail non-fuel base revenues increased primarily due to rate changes which include (i) a $3.8 million increase related to the 1% increase in the City of El Paso franchise fee on gross revenues for services within the City of El Paso, applicable to customer billings issued on or after October 1, 2018, (ii) $3.0 million of revenues in Texas for the period of July 30, 2019 through December 31, 2019, related to the TCRF settlement agreement approved by the PUCT in Docket No. 49148 on December 16, 2019, and (iii) a $2.0 million increase related to the DCRF settlement agreement approved by the PUCT in Docket No. 49395 on September 27, 2019, applicable to customer billings issued on or after October 1, 2019. Excluding the impact of rate changes, retail non-fuel base revenues for the twelve months ended December 31, 2019, increased $1.0 million, compared to the twelve months ended December 31, 2018. This increase was primarily due to increased revenues from residential customers of $1.4 million caused by a 0.3% increase in kWh sales, which primarily resulted from a 1.6% increase in the average number of residential customers served. Cooling degree days decreased 5.3% in the twelve months ended December 31, 2019, when compared to the twelve months ended December 31, 2018, but were 4.2% above the 10-year average. Heating degree days increased 10.0% in the twelve months ended December 31, 2019, when compared to the twelve months ended December 31, 2018, and were 3.7% above the 10-year average. For the twelve months ended December 31, 2018, retail non-fuel base revenues decreased primarily due to the refunds in 2018 of approximately $28.2 million to customers for the reduction in the federal corporate income tax rate due to the TCJA, partially offset by a $7.7 million base rate increase related to the 2017 PUCT Final Order. Excluding the impact of rate changes related to the 2017 PUCT Final Order, retail non-fuel base revenues increased by $19.8 million, or 3.2%, compared to the twelve months ended December 31, 2017. This increase was primarily due to (i) increased revenues from residential customers of $17.1 million caused by a 5.9% increase in kWh sales that resulted from favorable weather and a 1.7% increase in the average number of residential customers served, and (ii) increased revenues from small commercial and industrial customers of $2.9 million that resulted from favorable weather and a 0.9% increase in the average number of small commercial and industrial customers served. Cooling degree days increased 8.8% in the twelve months ended December 31, 2018, when compared to the twelve months ended December 31, 2017, and were 10.9% above the 10-year average. Heating degree days increased 27.3% in the twelve months ended December 31, 2018, when compared to the twelve months ended December 31, 2017, and were 5.8% below the 10-year average. Fuel revenues . Fuel revenues are earned as and generally limited to fuel and purchased power costs incurred. Fuel revenues decreased $57.5 million for the twelve months ended December 31, 2019 when compared to the twelve months ended December 31, 2018, while fuel and purchased power expense declined $53.2 million in the same period. These declines are primarily attributable to a 41.3% decline in the cost of natural gas. Fuel revenues consist of revenues collected from customers under fuel recovery mechanisms approved by the state commissions and the FERC, and deferred fuel revenues, which are comprised of the difference between fuel costs and fuel revenues collected from customers. In New Mexico, fuel and purchased power costs, net of the cost of off-system sales and related shared margins, are reconciled to actual costs on a monthly basis and recovered or refunded to customers the second succeeding month. Additionally, effective January 1, 2018, pursuant to the final order in NMPRC Case No. 17-00090-UT, the RPS costs for New Mexico are recovered through a separate RPS Cost Rider, which is updated annually. In Texas, fuel and purchased power costs, net of shared margins on off-system sales, are recovered through a fixed fuel factor. We can seek to revise our Texas fixed fuel factor based upon an approved formula at least four months after our last revision, except in the month of December. In addition, if we materially over-recover fuel costs, we must seek to refund the over-recovery, and if we materially under-recover fuel costs, we may seek a surcharge to recover those costs. Fuel over- and under-recoveries are defined as material when they exceed 4% of the previous twelve months' fuel costs. In June 2019, March 2018 and March 2017, $1.0 million, $1.1 million and $1.4 million, respectively, were credited to customers through the applicable fuel adjustment clauses as the result of a reimbursement from the DOE related to spent nuclear fuel storage. Off-system sales.  Off-system sales are sales into wholesale markets outside our service territory. Off-system sales are primarily made in off- peak periods when we have competitive generation capacity available after meeting our regulated service obligations. We have shared 100% of margins on non-arbitrage sales (as defined by the settlement approved in PUCT Docket No. 41852) and 50% of margins on arbitrage sales with our Texas customers since April 1, 2014. We are currently sharing 90% of off-system sales margins with our New Mexico customers (as reaffirmed in NMPRC Case No. 09-00171-UT), and 25% of our off-system sales margins with our sales for resale - full requirement customer under the terms of their contract. Typically, we realize a significant portion of our off-system sales margins in the first and fourth quarter of each calendar year when our native load is lower than at other times of the year, allowing for the sale in the wholesale market of relatively larger amounts of off-system energy generated from lower cost generating resources. A decrease in natural gas market prices coupled with an increase in wholesale power market prices allowed us to engage in additional off-system sales in the first and fourth quarters of 2019. A decrease in natural gas market prices coupled with an increase in wholesale power market prices allowed us 33