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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2018
Asset Retirement Obligations [Line Items] |
Schedule of Asset Retirement Obligations by Category | The following table presents the AROs recorded on the Consolidated Balance Sheets.
| December 31, 2018
|  |  | Duke |  |  |  |  | Duke |  |  | Duke |  |  | Duke |  |  | Duke |  |  |
| Duke |  |  | Energy |  |  | Progress |  |  | Energy |  |  | Energy |  |  | Energy |  |  | Energy |  |  |
(in millions) | Energy |  |  | Carolinas |  |  | Energy |  |  | Progress |  |  | Florida |  |  | Ohio |  |  | Indiana |  |  | Piedmont |
Decommissioning of nuclear power facilities(a) | $ | 5,696 |  |  | $ | 2,335 |  |  | $ | 3,209 |  |  | $ | 2,679 |  |  | $ | 530 |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Closure of ash impoundments | 4,446 |  |  | 1,568 |  |  | 2,123 |  |  | 2,103 |  |  | 20 |  |  | 52 |  |  | 702 |  |  | — |
Other(b) | 325 |  |  | 46 |  |  | 79 |  |  | 38 |  |  | 41 |  |  | 41 |  |  | 20 |  |  | 19 |
Total asset retirement obligation | $ | 10,467 |  |  | $ | 3,949 |  |  | $ | 5,411 |  |  | $ | 4,820 |  |  | $ | 591 |  |  | $ | 93 |  |  | $ | 722 |  |  | $ | 19 |
Less: current portion | 919 |  |  | 290 |  |  | 514 |  |  | 509 |  |  | 5 |  |  | 6 |  |  | 109 |  |  | — |
Total noncurrent asset retirement obligation | $ | 9,548 |  |  | $ | 3,659 |  |  | $ | 4,897 |  |  | $ | 4,311 |  |  | $ | 586 |  |  | $ | 87 |  |  | $ | 613 |  |  | $ | 19 |
(a) | Duke Energy amount includes purchase accounting adjustments related to the merger with Progress Energy.
(b) | Primarily includes obligations related to asbestos removal. Duke Energy Ohio and Piedmont also include AROs related to the retirement of natural gas mains and services. Duke Energy includes AROs related to the removal of renewable energy generation assets.
Public Utilities General Disclosures | The following table includes the current expiration of nuclear operating licenses.
Unit | Year of Expiration
Duke Energy Carolinas |
Catawba Units 1 and 2 | 2043
McGuire Unit 1 | 2041
McGuire Unit 2 | 2043
Oconee Units 1 and 2 | 2033
Oconee Unit 3 | 2034
Duke Energy Progress |
Brunswick Unit 1 | 2036
Brunswick Unit 2 | 2034
Harris | 2046
Robinson | 2030
The following table presents the fair value of NDTF assets legally restricted for purposes of settling AROs associated with nuclear decommissioning. Duke Energy Florida is actively decommissioning Crystal River Unit 3 and was granted an exemption from the NRC, which allows for use of the NDTF for all aspects of nuclear decommissioning. The entire balance of Duke Energy Florida's NDTF may be applied toward license termination, spent fuel and site restoration costs incurred to decommission Crystal River Unit 3 and is excluded from the table below. See Note 16 for additional information related to the fair value of the Duke Energy Registrants' NDTFs.
| December 31,
(in millions) | 2018 |  | 2017
Duke Energy | $ | 5,579 |  |  | $ | 5,864 |
Duke Energy Carolinas | 3,133 |  |  | 3,321 |
Duke Energy Progress | 2,446 |  |  | 2,543 |
The following table summarizes information about the most recent site-specific nuclear decommissioning cost studies. Decommissioning costs are stated in 2018 dollars for Duke Energy Carolinas, 2017 dollars for Duke Energy Florida and 2014 dollars for Duke Energy Progress, and include costs to decommission plant components not subject to radioactive contamination.
| Annual Funding |  |  | Decommissioning |  |  |
(in millions) | Requirement(a) |  |  | Costs(a) |  |  | Year of Cost Study
Duke Energy | $ | 24 |  |  | $ | 8,737 |  |  | 2014 and 2018
Duke Energy Carolinas(b)(c) | — |  |  | 4,291 |  |  | 2018
Duke Energy Progress | 24 |  |  | 3,550 |  |  | 2014
Duke Energy Florida(d) | — |  |  | 896 |  |  | 2018
(a) | Amounts for Progress Energy equal the sum of Duke Energy Progress and Duke Energy Florida.
(b) | Decommissioning cost for Duke Energy Carolinas reflects its ownership interest in jointly owned reactors. Other joint owners are responsible for decommissioning costs related to their interest in the reactors.
(c) | Duke Energy Carolinas' site-specific nuclear decommissioning cost study completed in 2018 is expected to be filed with the NCUC and PSCSC by the second quarter 2019. Duke Energy Carolinas will also complete a new funding study, which will be completed and filed with the NCUC and PSCSC in 2019.
(d) | Duke Energy Florida's site-specific nuclear decommissioning cost study and a new funding study were completed and filed with the FPSC in 2018.
Rollforward Schedule of Asset Retirement Obligations | The following tables present changes in the liability associated with AROs.
|  |  | 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, 2016 | $ | 10,611 |  |  | $ | 3,895 |  |  | $ | 5,475 |  |  | $ | 4,697 |  |  | $ | 778 |  |  | $ | 77 |  |  | $ | 866 |  |  | $ | 14 |
Accretion expense(a) | 435 |  |  | 184 |  |  | 228 |  |  | 195 |  |  | 33 |  |  | 3 |  |  | 32 |  |  | 1 |
Liabilities settled(b) | (619 | ) |  | (282 | ) |  | (270 | ) |  | (204 | ) |  | (65 | ) |  | (7 | ) |  | (49 | ) |  | (8 | )
Liabilities incurred in the current year(c) | 51 |  |  | 5 |  |  | — |  |  | — |  |  | — |  |  | 7 |  |  | 29 |  |  | 8 |
Revisions in estimates of cash flows | (303 | ) |  | (192 | ) |  | (19 | ) |  | (15 | ) |  | (4 | ) |  | 4 |  |  | (97 | ) |  | — |
Balance at December 31, 2017 | 10,175 |  |  | 3,610 |  |  | 5,414 |  |  | 4,673 |  |  | 742 |  |  | 84 |  |  | 781 |  |  | 15 |
Accretion expense(a) | 427 |  |  | 179 |  |  | 225 |  |  | 196 |  |  | 29 |  |  | 4 |  |  | 29 |  |  | 1 |
Liabilities settled(b) | (638 | ) |  | (281 | ) |  | (272 | ) |  | (227 | ) |  | (45 | ) |  | (5 | ) |  | (79 | ) |  | — |
Liabilities incurred in the current year(c) | 39 |  |  | 8 |  |  | 5 |  |  | — |  |  | 5 |  |  | — |  |  | 25 |  |  | — |
Revisions in estimates of cash flows(d) | 464 |  |  | 433 |  |  | 39 |  |  | 178 |  |  | (140 | ) |  | 10 |  |  | (34 | ) |  | 3 |
Balance at December 31, 2018 | $ | 10,467 |  |  | $ | 3,949 |  |  | $ | 5,411 |  |  | $ | 4,820 |  |  | $ | 591 |  |  | $ | 93 |  |  | $ | 722 |  |  | $ | 19 |
(a) | Substantially all accretion expense for the years ended December 31, 2018, and 2017 relates to Duke Energy’s regulated operations and has been deferred in accordance with regulatory accounting treatment.
(b) | Amounts primarily relate to ash impoundment closures and nuclear decommissioning of Crystal River Unit 3.
(c) | Amounts primarily relate to AROs recorded as a result of state agency closure requirements at Duke Energy Indiana.
(d) | Amounts primarily relate to increases in groundwater monitoring estimates for closure of ash impoundments and an increase for nuclear decommissioning costs at Duke Energy Carolinas' nuclear sites compared to original estimates, partially offset by a reduction for nuclear decommissioning at Crystal River Unit 3 compared to original estimates and modifications to the timing of expected cash flows for coal ash AROs.

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