| Segment Information |
Segment Information We assess our business on a regional basis due to the impact on our financial performance of the differing characteristics of these regions, particularly with respect to competition, regulation and other factors impacting supply and demand. At September 30, 2015, our reportable segments were West (including geothermal), Texas and East (including Canada). We continue to evaluate the manner in which we assess our performance, including our segments, which may result in future changes to the composition of our geographic segments. Commodity Margin is a key operational measure reviewed by our chief operating decision maker to assess the performance of our segments. The tables below show our financial data for our segments for the periods indicated (in millions). | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, 2015 | | West | | Texas | | East | | Consolidation and Elimination | | Total | Revenues from external customers | $ | 736 |
| | $ | 709 |
| | $ | 503 |
| | $ | — |
| | $ | 1,948 |
| Intersegment revenues | 1 |
| | 4 |
| | 3 |
| | (8 | ) | | — |
| Total operating revenues | $ | 737 |
| | $ | 713 |
| | $ | 506 |
| | $ | (8 | ) | | $ | 1,948 |
| Commodity Margin | $ | 385 |
| | $ | 264 |
| | $ | 325 |
| | $ | — |
| | $ | 974 |
| Add: Mark-to-market commodity activity, net and other(1) | 68 |
| | (98 | ) | | (62 | ) | | (7 | ) | | (99 | ) | Less: | | | | | | | | | | Plant operating expense | 87 |
| | 62 |
| | 57 |
| | (6 | ) | | 200 |
| Depreciation and amortization expense | 61 |
| | 58 |
| | 48 |
| | (1 | ) | | 166 |
| Sales, general and other administrative expense | 7 |
| | 15 |
| | 10 |
| | 1 |
| | 33 |
| Other operating expenses | 8 |
| | 2 |
| | 8 |
| | (2 | ) | | 16 |
| (Income) from unconsolidated investments in power plants | — |
| | — |
| | (6 | ) | | — |
| | (6 | ) | Income from operations | 290 |
| | 29 |
| | 146 |
| | 1 |
| | 466 |
| Interest expense, net of interest income | | | | | | | | | 158 |
| Other (income) expense, net | | | | | | | | | 1 |
| Income before income taxes | | | | | | | | | $ | 307 |
|
| | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, 2014 | | West | | Texas | | East | | Consolidation and Elimination | | Total | Revenues from external customers | $ | 714 |
| | $ | 985 |
| | $ | 488 |
| | $ | — |
| | $ | 2,187 |
| Intersegment revenues | 1 |
| | 4 |
| | 2 |
| | (7 | ) | | — |
| Total operating revenues | $ | 715 |
| | $ | 989 |
| | $ | 490 |
| | $ | (7 | ) | | $ | 2,187 |
| Commodity Margin(2) | $ | 361 |
| | $ | 346 |
| | $ | 237 |
| | $ | — |
| | $ | 944 |
| Add: Mark-to-market commodity activity, net and other(1) | 41 |
| | (64 | ) | | 4 |
| | (6 | ) | | (25 | ) | Less: | | | | | | | | | | Plant operating expense | 91 |
| | 77 |
| | 55 |
| | (8 | ) | | 215 |
| Depreciation and amortization expense | 65 |
| | 51 |
| | 38 |
| | (1 | ) | | 153 |
| Sales, general and other administrative expense | 11 |
| | 18 |
| | 8 |
| | — |
| | 37 |
| Other operating expenses | 12 |
| | 1 |
| | 6 |
| | 4 |
| | 23 |
| Impairment losses | — |
| | — |
| | 123 |
| | — |
| | 123 |
| (Gain) on sale of assets, net | — |
| | — |
| | (753 | ) | | — |
| | (753 | ) | (Income) from unconsolidated investments in power plants | — |
| | — |
| | (5 | ) | | — |
| | (5 | ) | Income from operations | 223 |
| | 135 |
| | 769 |
| | (1 | ) | | 1,126 |
| Interest expense, net of interest income | | | | | | | | | 154 |
| Debt extinguishment costs and other (income) expense, net | | | | | | | | | 344 |
| Income before income taxes | | | | | | | | | $ | 628 |
|
| | | | | | | | | | | | | | | | | | | | | | Nine Months Ended September 30, 2015 | | West | | Texas | | East | | Consolidation and Elimination | | Total | Revenues from external customers | $ | 1,672 |
| | $ | 1,860 |
| | $ | 1,504 |
| | $ | — |
| | $ | 5,036 |
| Intersegment revenues | 3 |
| | 12 |
| | 7 |
| | (22 | ) | | — |
| Total operating revenues | $ | 1,675 |
| | $ | 1,872 |
| | $ | 1,511 |
| | $ | (22 | ) | | $ | 5,036 |
| Commodity Margin | $ | 843 |
| | $ | 583 |
| | $ | 740 |
| | $ | — |
| | $ | 2,166 |
| Add: Mark-to-market commodity activity, net and other(3) | 173 |
| | (47 | ) | | (84 | ) | | (21 | ) | | 21 |
| Less: | | | | | | | | | | Plant operating expense | 313 |
| | 233 |
| | 206 |
| | (20 | ) | | 732 |
| Depreciation and amortization expense | 193 |
| | 157 |
| | 135 |
| | (1 | ) | | 484 |
| Sales, general and other administrative expense | 23 |
| | 47 |
| | 29 |
| | 1 |
| | 100 |
| Other operating expenses | 28 |
| | 6 |
| | 24 |
| | (2 | ) | | 56 |
| (Income) from unconsolidated investments in power plants | — |
| | — |
| | (18 | ) | | — |
| | (18 | ) | Income from operations | 459 |
| | 93 |
| | 280 |
| | 1 |
| | 833 |
| Interest expense, net of interest income | | | | | | | | | 468 |
| Debt modification and extinguishment costs and other (income) expense, net | | | | | | | | | 40 |
| Income before income taxes | | | | | | | | | $ | 325 |
|
| | | | | | | | | | | | | | | | | | | | | | Nine Months Ended September 30, 2014 | | West | | Texas | | East | | Consolidation and Elimination | | Total | Revenues from external customers | $ | 1,692 |
| | $ | 2,592 |
| | $ | 1,807 |
| | $ | — |
| | $ | 6,091 |
| Intersegment revenues | 4 |
| | 19 |
| | 46 |
| | (69 | ) | | — |
| Total operating revenues | $ | 1,696 |
| | $ | 2,611 |
| | $ | 1,853 |
| | $ | (69 | ) | | $ | 6,091 |
| Commodity Margin(2) | $ | 791 |
| | $ | 644 |
| | $ | 786 |
| | $ | — |
| | $ | 2,221 |
| Add: Mark-to-market commodity activity, net and other(3) | 91 |
| | 74 |
| | (31 | ) | | (23 | ) | | 111 |
| Less: | | | | | | | | | | Plant operating expense | 291 |
| | 250 |
| | 237 |
| | (24 | ) | | 754 |
| Depreciation and amortization expense | 183 |
| | 141 |
| | 129 |
| | — |
| | 453 |
| Sales, general and other administrative expense | 28 |
| | 48 |
| | 32 |
| | — |
| | 108 |
| Other operating expenses | 39 |
| | 4 |
| | 22 |
| | 1 |
| | 66 |
| Impairment losses | — |
| | — |
| | 123 |
| | — |
| | 123 |
| (Gain) on sale of assets, net | — |
| | — |
| | (753 | ) | | — |
| | (753 | ) | (Income) from unconsolidated investments in power plants | — |
| | — |
| | (18 | ) | | — |
| | (18 | ) | Income from operations | 341 |
|
| 275 |
|
| 983 |
|
| — |
| | 1,599 |
| Interest expense, net of interest income | | | | | | | | | 486 |
| Debt extinguishment costs and other (income) expense, net | | | | | | | | | 361 |
| Income before income taxes | | | | | | | | | $ | 752 |
|
_________ | | (1) | Includes $41 million and $49 million of lease levelization and $4 million and $4 million of amortization expense for the three months ended September 30, 2015 and 2014, respectively. |
| | (2) | Commodity Margin related to the six power plants sold in our East segment on July 3, 2014, was not significant for the three months ended September 30, 2014. The Commodity Margin related to those power plants was $81 million for the nine months ended September 30, 2014. |
| | (3) | Includes $(1) million and $(7) million of lease levelization and $11 million and $11 million of amortization expense for the nine months ended September 30, 2015 and 2014, respectively. |
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