Revenues

On January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), for all of its contracts using the modified retrospective method. There was no cumulative effect adjustment at the initial application of the new standard. In addition, comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company expects the ongoing impact of the new standard to be immaterial to net income and no significant changes in the Company's business processes and internal controls were necessary upon adoption of the new standard.

The following table disaggregates revenue from contracts with customers, for the twelve months ended December 31, 2018 (in thousands):



	December 31, 2018
	Twelve Months Ended
Retail	$	789,676
Wholesale	90,673
Wheeling (transmission)	19,026
Total revenues from contracts with customers	899,375
Other	4,228
Total operating revenues	$	903,603

The Company recognizes revenue when performance obligations under the terms of the contract with the customer are satisfied. Revenue is measured as the amount of consideration the Company receives in exchange for transferring goods or providing services to the customer. Taxes collected concurrently with revenue producing activities are excluded from revenue. The Company has elected the optional invoice practical expedient for Wholesale and Wheeling revenues, as the invoice amount will correspond directly to the value provided by the Company's performance to date.

Retail. Retail contracts represent the Company's primary revenue source. The Company has determined that retail electric service to residential, commercial and industrial, and public authority customers represents an implied daily contract with the customer. The contract is comprised of an obligation to supply and distribute electricity and related capacity. Revenue is recognized, over time, equal to the product of the applicable tariff rates, as approved by the PUCT and the NMPRC, and the volume of the electricity delivered to the customer, or through the passage of time based upon providing the service of standing ready. Unbilled revenues are recognized at month end based on estimated monthly generation volumes and by applying an average revenue per kWh to the number of estimated kWhs delivered but not billed to customers, and recorded as a receivable for the period following the last billing cycle to the end of the reporting period. Retail customers receive a bill monthly, with payment due sixteen days after issuance.

Wholesale. Wholesale contracts primarily include forward power sales into markets outside the Company’s service territory when the Company has competitive generation capacity available, after meeting its regulated service obligations. Pricing is either fixed or based on an index rate with consideration potentially including variable components. Uncertainties regarding the variable consideration will be resolved when the transaction price is known at the point of delivering the energy. The obligation to deliver the electricity is satisfied over time as the customer receives and consumes the electricity. Wholesale customers are invoiced monthly on the 10^th day of each month, with payment due by the 20^th day of the month. In the case of the sale of renewable energy certificates, the transaction price is allocated to the performance obligation to deliver the confirmed quantity of the certificates based on the stand alone selling price of each certificate. Revenue is recognized as control of the certificates is transferred to the customer. The customer is invoiced upon the completed transfer of the certificates, with payment due within ten business days. Wholesale also includes an annual agreement between the Company and one of its wholesale customers, Rio Grande Electric Cooperative ("RGEC"), which involves the provision of full requirements electric service from the Company to RGEC. The rates for this service are recalculated annually and require FERC approval.

Wheeling (transmission). Wheeling involves the Company providing point-to-point transmission service, which includes the receipt of capacity and energy at designated point(s) and the transfer of such capacity and energy to designated point(s) of delivery on either a firm or non-firm basis for periods of one year or less. The performance obligation to provide capacity and transmit energy is satisfied over time as the Company performs. Transmission customers are invoiced on a monthly basis, with payment due within twenty days of receipt of the invoice.

Other. Other includes alternative revenue program revenue relating to the Company’s potential bonus awards from the PUCT and the NMPRC mandated energy efficiency programs. Both the PUCT and the NMPRC allow for the potential to earn an incentive bonus if the Company achieves its approved energy efficiency goals under the applicable programs. The Company recognizes revenue related to the energy efficiency program incentives at the point in time that the amount is objectively determinable generally based upon an approved order from the regulator, is probable of recovery, and if it is expected to be collected within 24 months. Other revenue also includes (i) late payment fees, (ii) leasing income, and (iii) the Company’s allocated share, based on ownership, of sales of surplus effluent water from Palo Verde.

Accounts receivable. Accounts receivable is principally comprised of revenue from contracts with customers. The Company recognizes expense for accounts that are deemed uncollectible in operating expense. The Company recognized $2.9 million of uncollectible expense for the twelve months ended December 31, 2018.