XML 82 R26.htm IDEA: XBRL DOCUMENT
v3.20.4

Revenue | 12 Months Ended
--- | ---
Dec. 31, 2020
Revenue from Contract with Customer [Abstract] |
Revenue | REVENUE Duke Energy recognizes revenue consistent with amounts billed under tariff offerings or at contractually agreed upon rates based on actual physical delivery of electric or natural gas service, including estimated volumes delivered when billings have not yet occurred. As such, the majority of Duke Energy’s revenues have fixed pricing based on the contractual terms of the published tariffs, with variability in expected cash flows attributable to the customer’s volumetric demand and ultimate quantities of energy or natural gas supplied and used during the billing period. The stand-alone selling price of related sales are designed to support recovery of prudently incurred costs and an appropriate return on invested assets and are primarily governed by published tariff rates or contractual agreements approved by relevant regulatory bodies. As described in Note 1, certain excise taxes and franchise fees levied by state or local governments are required to be paid even if not collected from the customer. These taxes are recognized on a gross basis as part of revenues. Duke Energy elects to account for all other taxes net of revenues. Performance obligations are satisfied over time as energy or natural gas is delivered and consumed with billings generally occurring monthly and related payments due within 30 days, depending on regulatory requirements. In no event does the timing between payment and delivery of the goods and services exceed one year. Using this output method for revenue recognition provides a faithful depiction of the transfer of electric and natural gas service as customers obtain control of the commodity and benefit from its use at delivery. Additionally, Duke Energy has an enforceable right to consideration for energy or natural gas delivered at any discrete point in time and will recognize revenue at an amount that reflects the consideration to which Duke Energy is entitled for the energy or natural gas delivered. As described above, the majority of Duke Energy’s tariff revenues are at-will and, as such, related contracts with customers have an expected duration of one year or less and will not have future performance obligations for disclosure. Additionally, other long-term revenue streams, including wholesale contracts, generally provide services that are part of a single performance obligation, the delivery of electricity or natural gas. As such, other than material fixed consideration under long-term contracts, related disclosures for future performance obligations are also not applicable. Duke Energy earns substantially all of its revenues through its reportable segments, Electric Utilities and Infrastructure, Gas Utilities and Infrastructure and Commercial Renewables. Electric Utilities and Infrastructure Electric Utilities and Infrastructure earns the majority of its revenues through retail and wholesale electric service through the generation, transmission, distribution and sale of electricity. Duke Energy generally provides retail and wholesale electric service customers with their full electric load requirements or with supplemental load requirements when the customer has other sources of electricity. Retail electric service is generally marketed throughout Duke Energy's electric service territory through standard service offers. The standard service offers are through tariffs determined by regulators in Duke Energy's regulated service territory. Each tariff, which is assigned to customers based on customer class, has multiple components such as an energy charge, a demand charge, a basic facilities charge and applicable riders. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing electric service, or in the case of distribution only customers in Duke Energy Ohio, for delivering electricity. Electricity is considered a single performance obligation satisfied over time consistent with the series guidance and is provided and consumed over the billing period, generally one month. Retail electric service is typically provided to at-will customers who can cancel service at any time, without a substantive penalty. Additionally, Duke Energy adheres to applicable regulatory requirements in each jurisdiction to ensure the collectability of amounts billed and appropriate mitigating procedures are followed when necessary. As such, revenue from contracts with customers for such contracts is equivalent to the electricity supplied and billed in that period (including unbilled estimates). Wholesale electric service is generally provided under long-term contracts using cost-based pricing. FERC regulates costs that may be recovered from customers and the amount of return companies are permitted to earn. Wholesale contracts include both energy and demand charges. For full requirements contracts, Duke Energy considers both charges as a single performance obligation for providing integrated electric service. For contracts where energy and demand charges are considered separate performance obligations, energy and demand are each a distinct performance obligation under the series guidance and are satisfied as energy is delivered and stand-ready service is provided on a monthly basis. This service represents consumption over the billing period and revenue is recognized consistent with billings and unbilled estimates, which generally occur monthly. Contractual amounts owed are typically trued up annually based upon incurred costs in accordance with FERC published filings and the specific customer’s actual peak demand. Estimates of variable consideration related to potential additional billings or refunds owed are updated quarterly. The majority of wholesale revenues are full requirements contracts where the customers purchase the substantial majority of their energy needs and do not have a fixed quantity of contractually required energy or capacity. As such, related forecasted revenues are considered optional purchases. Supplemental requirements contracts that include contracted blocks of energy and capacity at contractually fixed prices have the following estimated remaining performance obligations:
| Remaining Performance Obligations
(in millions) | 2021 | 2022 | 2023 | 2024 | 2025 | Thereafter | Total
Progress Energy | $ | 93 |  | $ | 107 |  | $ | 44 |  | $ | 45 |  | $ | 7 |  | $ | 51 |  | $ | 347 |
Duke Energy Progress | 8 |  | 8 |  | 8 |  | 8 |  | — |  | — |  | 32 |
Duke Energy Florida | 85 |  | 99 |  | 36 |  | 37 |  | 7 |  | 51 |  | 315 |
Duke Energy Indiana | 5 |  | — |  | 7 |  | 12 |  | 12 |  | 24 |  | 60 |
Revenues for block sales are recognized monthly as energy is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Gas Utilities and Infrastructure Gas Utilities and Infrastructure earns its revenue through retail and wholesale natural gas service through the transportation, distribution and sale of natural gas. Duke Energy generally provides retail and wholesale natural gas service customers with all natural gas load requirements. Additionally, while natural gas can be stored, substantially all natural gas provided by Duke Energy is consumed by customers simultaneously with receipt of delivery. Retail natural gas service is marketed throughout Duke Energy's natural gas service territory using published tariff rates. The tariff rates are established by regulators in Duke Energy's service territories. Each tariff, which is assigned to customers based on customer class, have multiple components, such as a commodity charge, demand charge, customer or monthly charge and transportation costs. Duke Energy considers each of these components to be aggregated into a single performance obligation for providing natural gas service. For contracts where Duke Energy provides all of the customer’s natural gas needs, the delivery of natural gas is considered a single performance obligation satisfied over time, and revenue is recognized monthly based on billings and unbilled estimates as service is provided and the commodity is consumed over the billing period. Additionally, natural gas service is typically at-will and customers can cancel service at any time, without a substantive penalty. Duke Energy also adheres to applicable regulatory requirements to ensure the collectability of amounts billed and receivable and appropriate mitigating procedures are followed when necessary. Certain long-term individually negotiated contracts exist to provide natural gas service. These contracts are regulated and approved by state commissions. The negotiated contracts have multiple components, including a natural gas and a demand charge, similar to retail natural gas contracts. Duke Energy considers each of these components to be a single performance obligation for providing natural gas service. This service represents consumption over the billing period, generally one month. Fixed capacity payments under long-term contracts for the Gas Utilities and Infrastructure segment include minimum margin contracts and supply arrangements with municipalities and power generation facilities. Revenues for related sales are recognized monthly as natural gas is delivered and stand-ready service is provided, consistent with invoiced amounts and unbilled estimates. Estimated remaining performance obligations are as follows:
| Remaining Performance Obligations
(in millions) | 2021 | 2022 | 2023 | 2024 | 2025 | Thereafter | Total
Piedmont | $ | 65 |  | $ | 64 |  | $ | 61 |  | $ | 59 |  | $ | 58 |  | $ | 319 |  | $ | 626 |
Commercial Renewables Commercial Renewables earns the majority of its revenues through long-term PPAs and generally sells all of its wind and solar facility output, electricity and RECs to customers. The majority of these PPAs have historically been accounted for as leases. For PPAs that are not accounted for as leases, the delivery of electricity and the delivery of RECs are considered separate performance obligations. The delivery of electricity is a performance obligation satisfied over time and represents generation and consumption of the electricity over the billing period, generally one month. The delivery of RECs is a performance obligation satisfied at a point in time and represents delivery of each REC generated by the wind or solar facility. The majority of self-generated RECs are bundled with energy in Duke Energy’s contracts and, as such, related revenues are recognized as energy is generated and delivered as that pattern is consistent with Duke Energy’s performance. Commercial Renewables recognizes revenue based on the energy generated and billed for the period, generally one month, at contractual rates (including unbilled estimates) according to the invoice practical expedient. Amounts are typically due within 30 days of invoice. Commercial Renewables also earns revenues from installation of distributed solar generation resources, which is primarily composed of EPC projects to deliver functioning solar power systems, generally completed within two to 12 months from commencement of construction. The installation of distributed solar generation resources is a performance obligation that is satisfied over time. Revenue from fixed-price EPC contracts is recognized using the input method as work is performed based on the estimated ratio of incurred costs to estimated total costs. Other The remainder of Duke Energy’s operations is presented as Other, which does not include material revenues from contracts with customers. Disaggregated Revenues For the Electric and Gas Utility and Infrastructure segments, revenue by customer class is most meaningful to Duke Energy as each respective customer class collectively represents unique customer expectations of service, generally has different energy and demand requirements, and operates under tailored, regulatory approved pricing structures. Additionally, each customer class is impacted differently by weather and a variety of economic factors including the level of population growth, economic investment, employment levels, and regulatory activities in each of Duke Energy’s jurisdictions. As such, analyzing revenues disaggregated by customer class allows Duke Energy to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. For the Commercial Renewables segment, the majority of revenues from contracts with customers are from selling all of the unit-contingent output at contractually defined pricing under long-term PPAs with consistent expectations regarding the timing and certainty of cash flows. Disaggregated revenues are presented as follows:
| Year Ended December 31, 2020
|  | Duke |  | Duke | Duke | Duke | Duke |
(in millions) | Duke | Energy | Progress | Energy | Energy | Energy | Energy |
By market or type of customer | Energy | Carolinas | Energy | Progress | Florida | Ohio | Indiana | Piedmont
Electric Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 9,806 |  | $ | 2,997 |  | $ | 5,017 |  | $ | 2,059 |  | $ | 2,958 |  | $ | 726 |  | $ | 1,064 |  | $ | — |
General | 6,194 |  | 2,233 |  | 2,779 |  | 1,312 |  | 1,467 |  | 442 |  | 740 |  | — |
Industrial | 2,859 |  | 1,137 |  | 901 |  | 649 |  | 252 |  | 137 |  | 683 |  | — |
Wholesale | 1,864 |  | 380 |  | 1,228 |  | 1,034 |  | 194 |  | 32 |  | 224 |  | — |
Other revenues | 914 |  | 281 |  | 596 |  | 294 |  | 302 |  | 82 |  | 72 |  | — |
Total Electric Utilities and Infrastructure revenue from contracts with customers | $ | 21,637 |  | $ | 7,028 |  | $ | 10,521 |  | $ | 5,348 |  | $ | 5,173 |  | $ | 1,419 |  | $ | 2,783 |  | $ | — |
Gas Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 930 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 300 |  | $ | — |  | $ | 630 |
Commercial | 446 |  | — |  | — |  | — |  | — |  | 117 |  | — |  | 329 |
Industrial | 127 |  | — |  | — |  | — |  | — |  | 17 |  | — |  | 110 |
Power Generation | — |  | — |  | — |  | — |  | — |  | — |  | — |  | 34 |
Other revenues | 87 |  | — |  | — |  | — |  | — |  | 17 |  | — |  | 70 |
Total Gas Utilities and Infrastructure revenue from contracts with customers | $ | 1,590 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 451 |  | $ | — |  | $ | 1,173 |
Commercial Renewables |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 227 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Other |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 26 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Total revenue from contracts with customers | $ | 23,480 |  | $ | 7,028 |  | $ | 10,521 |  | $ | 5,348 |  | $ | 5,173 |  | $ | 1,870 |  | $ | 2,783 |  | $ | 1,173 |
Other revenue sources(a) | $ | 388 |  | $ | (13) |  | $ | 106 |  | $ | 74 |  | $ | 15 |  | $ | (12) |  | $ | 12 |  | $ | 124 |
Total revenues | $ | 23,868 |  | $ | 7,015 |  | $ | 10,627 |  | $ | 5,422 |  | $ | 5,188 |  | $ | 1,858 |  | $ | 2,795 |  | $ | 1,297 |
(a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Alternative revenue programs in certain jurisdictions include regulatory mechanisms that periodically adjust for over or under collection of related revenues.
| Year Ended December 31, 2019
|  | Duke |  | Duke | Duke | Duke | Duke |
(in millions) | Duke | Energy | Progress | Energy | Energy | Energy | Energy |
By market or type of customer | Energy | Carolinas | Energy | Progress | Florida | Ohio | Indiana | Piedmont
Electric Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 9,863 |  | $ | 3,044 |  | $ | 4,998 |  | $ | 2,144 |  | $ | 2,854 |  | $ | 733 |  | $ | 1,087 |  | $ | — |
General | 6,431 |  | 2,244 |  | 2,935 |  | 1,368 |  | 1,567 |  | 451 |  | 802 |  | — |
Industrial | 3,071 |  | 1,215 |  | 934 |  | 675 |  | 259 |  | 147 |  | 774 |  | — |
Wholesale | 2,212 |  | 462 |  | 1,468 |  | 1,281 |  | 187 |  | 46 |  | 235 |  | — |
Other revenues | 770 |  | 276 |  | 548 |  | 317 |  | 231 |  | 80 |  | 89 |  | — |
Total Electric Utilities and Infrastructure revenue from contracts with customers | $ | 22,347 |  | $ | 7,241 |  | $ | 10,883 |  | $ | 5,785 |  | $ | 5,098 |  | $ | 1,457 |  | $ | 2,987 |  | $ | — |
Gas Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 976 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 315 |  | $ | — |  | $ | 661 |
Commercial | 508 |  | — |  | — |  | — |  | — |  | 130 |  | — |  | 378 |
Industrial | 141 |  | — |  | — |  | — |  | — |  | 19 |  | — |  | 122 |
Power Generation | — |  | — |  | — |  | — |  | — |  | — |  | — |  | 51 |
Other revenues | 129 |  | — |  | — |  | — |  | — |  | 19 |  | — |  | 110 |
Total Gas Utilities and Infrastructure revenue from contracts with customers | $ | 1,754 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 483 |  | $ | — |  | $ | 1,322 |
Commercial Renewables |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 223 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Other |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 24 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Total revenue from contracts with customers | $ | 24,348 |  | $ | 7,241 |  | $ | 10,883 |  | $ | 5,785 |  | $ | 5,098 |  | $ | 1,940 |  | $ | 2,987 |  | $ | 1,322 |
Other revenue sources(a) | $ | 731 |  | $ | 154 |  | $ | 319 |  | $ | 172 |  | $ | 133 |  | $ | — |  | $ | 17 |  | $ | 59 |
Total revenues | $ | 25,079 |  | $ | 7,395 |  | $ | 11,202 |  | $ | 5,957 |  | $ | 5,231 |  | $ | 1,940 |  | $ | 3,004 |  | $ | 1,381 |
(a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Alternative revenue programs in certain jurisdictions include regulatory mechanisms that periodically adjust for over or under collection of related revenues.
| Year Ended December 31, 2018
|  | Duke |  | Duke | Duke | Duke | Duke |
(in millions) | Duke | Energy | Progress | Energy | Energy | Energy | Energy |
By market or type of customer | Energy | Carolinas | Energy | Progress | Florida | Ohio | Indiana | Piedmont
Electric Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 9,587 |  | $ | 2,981 |  | $ | 4,785 |  | $ | 2,019 |  | $ | 2,766 |  | $ | 743 |  | $ | 1,076 |  | $ | — |
General | 6,127 |  | 2,119 |  | 2,809 |  | 1,280 |  | 1,529 |  | 422 |  | 778 |  | — |
Industrial | 2,974 |  | 1,180 |  | 904 |  | 642 |  | 262 |  | 131 |  | 760 |  | — |
Wholesale | 2,324 |  | 508 |  | 1,462 |  | 1,303 |  | 159 |  | 57 |  | 298 |  | — |
Other revenues | 717 |  | 320 |  | 502 |  | 320 |  | 182 |  | 73 |  | 91 |  | — |
Total Electric Utilities and Infrastructure revenue from contracts with customers | $ | 21,729 |  | $ | 7,108 |  | $ | 10,462 |  | $ | 5,564 |  | $ | 4,898 |  | $ | 1,426 |  | $ | 3,003 |  | $ | — |
Gas Utilities and Infrastructure |  |  |  |  |  |  |  |
Residential | $ | 1,000 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 331 |  | $ | — |  | $ | 669 |
Commercial | 514 |  | — |  | — |  | — |  | — |  | 135 |  | — |  | 378 |
Industrial | 147 |  | — |  | — |  | — |  | — |  | 18 |  | — |  | 128 |
Power Generation | — |  | — |  | — |  | — |  | — |  | — |  | — |  | 54 |
Other revenues | 139 |  | — |  | — |  | — |  | — |  | 19 |  | — |  | 120 |
Total Gas Utilities and Infrastructure revenue from contracts with customers | $ | 1,800 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 503 |  | $ | — |  | $ | 1,349 |
Commercial Renewables |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 209 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | — |
Other |  |  |  |  |  |  |  |
Revenue from contracts with customers | $ | 19 |  | $ | — |  | $ | — |  | $ | — |  | $ | — |  | $ | 1 |  | $ | — |  | $ | — |
Total revenue from contracts with customers | $ | 23,757 |  | $ | 7,108 |  | $ | 10,462 |  | $ | 5,564 |  | $ | 4,898 |  | $ | 1,930 |  | $ | 3,003 |  | $ | 1,349 |
Other revenue sources(a) | $ | 764 |  | $ | 192 |  | $ | 266 |  | $ | 135 |  | $ | 123 |  | $ | 27 |  | $ | 56 |  | $ | 26 |
Total revenues | $ | 24,521 |  | $ | 7,300 |  | $ | 10,728 |  | $ | 5,699 |  | $ | 5,021 |  | $ | 1,957 |  | $ | 3,059 |  | $ | 1,375 |
(a) Other revenue sources include revenues from leases, derivatives and alternative revenue programs that are not considered revenues from contracts with customers. Alternative revenue programs in certain jurisdictions include regulatory mechanisms that periodically adjust for over or under collection of related revenues. As described in Note 1, Duke Energy adopted the new guidance for credit losses effective January 1, 2020, using the modified retrospective method of adoption, which does not require restatement of prior year reported results. The following table presents the reserve for credit losses for trade and other receivables based on adoption of the new standard.
| Year Ended December 31, 2020
|  | Duke |  | Duke | Duke | Duke | Duke |
| Duke | Energy | Progress | Energy | Energy | Energy | Energy |
(in millions) | Energy | Carolinas | Energy | Progress | Florida | Ohio | Indiana | Piedmont
Balance at December 31, 2019 | $ | 76 |  | $ | 10 |  | $ | 16 |  | $ | 8 |  | $ | 7 |  | $ | 4 |  | $ | 3 |  | $ | 6 |
Cumulative Change in Accounting Principle | 5 |  | 1 |  | 2 |  | 1 |  | 1 |  | — |  | — |  | 1 |
Write-Offs | (58) |  | (13) |  | (23) |  | (8) |  | (14) |  | — |  | — |  | (6) |
Credit Loss Expense | 75 |  | 13 |  | 29 |  | 9 |  | 20 |  | — |  | — |  | 11 |
Other Adjustments | 48 |  | 12 |  | 13 |  | 13 |  | — |  | — |  | — |  | — |
Balance at December 31, 2020 | $ | 146 |  | $ | 23 |  | $ | 37 |  | $ | 23 |  | $ | 14 |  | $ | 4 |  | $ | 3 |  | $ | 12 |
Trade and other receivables are evaluated based on an estimate of the risk of loss over the life of the receivable and current and historical conditions using supportable assumptions. Management evaluates the risk of loss for trade and other receivables by comparing the historical write-off amounts to total revenue over a specified period. Historical loss rates are adjusted due to the impact of current conditions, including the impacts of COVID-19, as well as forecasted conditions over a reasonable time period. The calculated write-off rate can be applied to the receivable balance for which an established reserve does not already exist. Management reviews the assumptions and risk of loss periodically for trade and other receivables. Due to the COVID-19 pandemic, as described in Note 1, certain jurisdictions have resumed standard billing and credit practices, disconnections for nonpayment and late payment charges, all of which were previously suspended in the first quarter of 2020. The specific actions taken by each Duke Energy Registrant are described in Note 3 and the impact of COVID-19 on certain receivables financing entities are described in Note 17. The impact of COVID-19 and Duke Energy’s related response on customers’ ability to pay for service is uncertain, and it is reasonably possible eventual write-offs of customer receivables may increase over current estimates. The aging of trade receivables is presented in the table below. Duke Energy considers receivables greater than 30 days outstanding past due.
| December 31, 2020
|  | Duke |  | Duke | Duke | Duke | Duke |
| Duke | Energy | Progress | Energy | Energy | Energy | Energy |
(in millions) | Energy | Carolinas | Energy | Progress | Florida | Ohio | Indiana | Piedmont
Unbilled Receivables | $ | 969 |  | $ | 328 |  | $ | 283 |  | $ | 167 |  | $ | 116 |  | $ | 2 |  | $ | 16 |  | $ | 86 |
0-30 days | 1,789 |  | 445 |  | 707 |  | 398 |  | 307 |  | 60 |  | 26 |  | 149 |
30-60 days | 185 |  | 80 |  | 54 |  | 25 |  | 29 |  | 8 |  | 3 |  | 8 |
60-90 days | 22 |  | 1 |  | 10 |  | 4 |  | 6 |  | 2 |  | 1 |  | 3 |
90+ days | 119 |  | 16 |  | 32 |  | 9 |  | 23 |  | 30 |  | 12 |  | 9 |
Deferred Payment Arrangements(a) | 215 |  | 96 |  | 80 |  | 52 |  | 28 |  | — |  | — |  | 7 |
Trade and Other Receivables | $ | 3,299 |  | $ | 966 |  | $ | 1,166 |  | $ | 655 |  | $ | 509 |  | $ | 102 |  | $ | 58 |  | $ | 262 |
(a) Due to certain customer financial hardships created by the COVID-19 pandemic and resulting stay-at-home orders, Duke Energy permitted customers to defer payment of past-due amounts through an installment payment plan over a period of several months. IMPACT OF WEATHER AND THE TIMING OF BILLING PERIODS Revenues and costs are influenced by seasonal weather patterns. Peak sales of electricity occur during the summer and winter months, which results in higher revenue and cash flows during these periods. By contrast, lower sales of electricity occur during the spring and fall, allowing for scheduled plant maintenance. Residential and general service customers are more impacted by weather than industrial customers. Estimated weather impacts are based on actual current period weather compared to normal weather conditions. Normal weather conditions are defined as the long-term average of actual historical weather conditions. Heating degree days measure the variation in weather based on the extent the average daily temperature falls below a base temperature. Cooling degree days measure the variation in weather based on the extent the average daily temperature rises above the base temperature. Each degree of temperature below the base temperature counts as one heating degree day and each degree of temperature above the base temperature counts as one cooling degree day. The estimated impact of weather on earnings for Electric Utilities and Infrastructure is based on the temperature variances from a normal condition and customers' historic usage patterns. The methodology used to estimate the impact of weather does not consider all variables that may impact customer response to weather conditions, such as humidity in the summer or wind chill in the winter. The precision of this estimate may also be impacted by applying long-term weather trends to shorter-term periods. Gas Utilities and Infrastructure's costs and revenues are influenced by seasonal patterns due to peak natural gas sales occurring during the winter months as a result of space heating requirements. Residential customers are the most impacted by weather. There are certain regulatory mechanisms for the North Carolina, South Carolina, Tennessee, Ohio and Kentucky service territories that normalize the margins collected from certain customer classes during the winter. In North Carolina, rate design provides protection from both weather and other usage variations such as conservation, while South Carolina, Tennessee and Kentucky revenues are adjusted solely based on weather. Ohio primarily employs a fixed charge each month regardless of the season and usage. UNBILLED REVENUE Unbilled revenues are recognized by applying customer billing rates to the estimated volumes of energy or natural gas delivered but not yet billed. Unbilled revenues can vary significantly from period to period as a result of seasonality, weather, customer usage patterns, customer mix, average price in effect for customer classes, timing of rendering customer bills and meter reading schedules, and the impact of weather normalization or margin decoupling mechanisms. Unbilled revenues are included within Receivables and Receivables of VIEs on the Consolidated Balance Sheets as shown in the following table.
| December 31,
(in millions) | 2020 |  | 2019
Duke Energy | $ | 969 |  |  | $ | 843 |
Duke Energy Carolinas | 328 |  |  | 298 |
Progress Energy | 283 |  |  | 217 |
Duke Energy Progress | 167 |  |  | 122 |
Duke Energy Florida | 116 |  |  | 95 |
Duke Energy Ohio | 2 |  |  | 1 |
Duke Energy Indiana | 16 |  |  | 16 |
Piedmont | 86 |  |  | 78 |
Additionally, Duke Energy Ohio and Duke Energy Indiana sell, on a revolving basis, nearly all of their retail accounts receivable, including receivables for unbilled revenues, to an affiliate, CRC and account for the transfers of receivables as sales. Accordingly, the receivables sold are not reflected on the Consolidated Balance Sheets of Duke Energy Ohio and Duke Energy Indiana. See Note 17 for further information. These receivables for unbilled revenues are shown in the table below.
| December 31,
(in millions) | 2020 |  | 2019
Duke Energy Ohio | $ | 87 |  |  | $ | 82 |
Duke Energy Indiana | 134 |  |  | 115 |

X
- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -URI http://asc.fasb.org/topic&trid=49130388 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 13 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 12 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 12 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045 + Details
Name: | us-gaap_RevenueFromContractWithCustomerTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration