Segment and Significant Customer Information

We assess our business on a regional basis due to the effect on our financial performance of the differing characteristics of these regions, particularly with respect to competition, regulation and other factors affecting supply and demand. During the first quarter of 2018, we altered the composition of our segments to report the results associated with our retail business as a separate segment. This change reflects the manner in which our segment information is presented internally to our chief operating decision maker associated with the strategic utilization of our retail business subsequent to the consummation of the Merger. Thus, beginning in the first quarter of 2018, our geographic reportable segments for our wholesale business are West (including geothermal), Texas and East (including Canada) and we have a separate reportable segment for our retail business. The tables below have been updated to present our segments on this revised basis for all periods. We continue to evaluate the optimal manner in which we assess our performance including our segments and future changes may result in changes to the composition of our geographic segments.

Commodity Margin is a key operational measure of profit reviewed by our chief operating decision maker to assess the performance of our segments. The tables below show our financial data for our segments (including a reconciliation of our Commodity Margin to income (loss) from operations by segment) for the periods indicated (in millions).



	Year Ended December 31, 2018
	Wholesale
	West			Texas			East			Retail		Consolidation and Elimination			Total
Total operating revenues⁽¹⁾	$	1,988		$	2,860		$	1,987		$	3,976	$	(1,299	)	$	9,512

Commodity Margin	$	1,060		$	646		$	970		$	357	$	—		$	3,033
Add: Mark-to-market commodity activity, net and other⁽²⁾	(165		)	(197		)	40			84		(32		)	(270		)
Less:
Operating and maintenance expense	348			272			269			163		(32		)	1,020
Depreciation and amortization expense	269			237			180			53		—			739
General and other administrative expense	40			61			38			19		—			158
Other operating expenses	42			24			32			—		—			98
Impairment losses	—			—			10			—		—			10
(Income) from unconsolidated subsidiaries	—			—			(26		)	2		—			(24		)
Income (loss) from operations	196			(145		)	507			204		—			762
Interest expense															617
(Gain) loss on extinguishment of debt and other (income) expense, net															53
Income before income taxes															$	92



	Year Ended December 31, 2017
	Wholesale
	West			Texas			East			Retail			Consolidation and Elimination			Total
Total operating revenues⁽¹⁾	$	1,881		$	2,342		$	1,658		$	3,797		$	(926	)	$	8,752

Commodity Margin	$	970		$	552		$	790		$	396		$	—		$	2,708
Add: Mark-to-market commodity activity, net and other⁽²⁾	(19		)	(174		)	(62		)	(10		)	(29		)	(294		)
Less:
Operating and maintenance expense	361			308			302			138			(29		)	1,080
Depreciation and amortization expense	240			208			201			75			—			724
General and other administrative expense	45			66			27			17			—			155
Other operating expenses	38			14			33			—			—			85
Impairment losses	28			13			—			—			—			41
(Gain) on sale of assets, net	—			—			(27		)	—			—			(27		)
(Income) from unconsolidated subsidiaries	—			—			(24		)	2			—			(22		)
Income (loss) from operations	239			(231		)	216			154			—			378
Interest expense																621
Debt modification and extinguishment costs and other (income) expense, net																70
Loss before income taxes																$	(313	)



	Year Ended December 31, 2016
	Wholesale
	West			Texas			East			Retail			Consolidation and Elimination			Total
Total operating revenues⁽¹⁾	$	1,545		$	2,145		$	1,657		$	1,520		$	(151	)	$	6,716

Commodity Margin	$	984		$	543		$	905		$	172		$	—		$	2,604
Add: Mark-to-market commodity activity, net and other⁽²⁾	(11		)	12			15			(62		)	(29		)	(75		)
Less:
Operating and maintenance expense	355			298			312			41			(29		)	977
Depreciation and amortization expense	224			205			214			19			—			662
General and other administrative expense	38			56			40			6			—			140
Other operating expenses	33			8			38			—			—			79
Impairment losses	13			—			—			—			—			13
(Gain) on sale of assets, net	—			—			(157		)	—			—			(157		)
(Income) from unconsolidated subsidiaries	—			—			(24		)	—			—			(24		)
Income (loss) from operations	310			(12		)	497			44			—			839
Interest expense																631
Debt modification and extinguishment costs and other (income) expense, net																49
Income before income taxes																$	159

__________


(1)	Includes intersegment revenues of $488 million, $324 million and $20 million in the West, $573 million, $361 million and $81 million in Texas, $234 million, $237 million and $48 million in the East and $4 million, $4 million, $2 million in Retail for the years ended December 31, 2018, 2017 and 2016, respectively.


(2)	Includes nil, $(8) million and $(2) million of lease levelization and $104 million, $178 million and $122 million of amortization expense for the years ended December 31, 2018, 2017 and 2016, respectively.

Significant Customers

For the year ended December 31, 2018, 2017 and 2016, we had no significant customer that individually accounted for more than 10% of our annual consolidated revenues.