Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule Of Remeasurements Of Deferred Income Taxes Due To Tax Reform [Table Text Block]

The one-time impacts recorded by the Registrants to remeasure their deferred income tax balances at the 21% corporate federal income tax rate as of December 31, 2017 are presented below:

						Successor
	Exelon(b)	Generation	ComEd	PECO	BGE	PHI	Pepco	DPL	ACE
Net Decrease to Deferred Income Tax Liability Balances	$8,624	$1,895	$2,819	$1,407	$1,120	$1,944	$968	$540	$456

						Successor
	Exelon	Generation	ComEd	PECO(c)	BGE	PHI	Pepco	DPL	ACE
Net Regulatory Liability Recorded(a)	$7,315	N/A	$2,818	$1,394	$1,124	$1,979	$976	$545	$458

						Successor
	Exelon(b)	Generation	ComEd	PECO	BGE	PHI	Pepco	DPL	ACE
Net Deferred Income Tax Benefit/(Expense) Recorded	$1,309	$1,895	$1	$13	$(4)	$(35)	$(8)	$(5)	$(2)

__________

(a) Reflects the net regulatory liabilities recorded on a pre-tax basis before taking into consideration the income tax benefits associated with the ultimate settlement with customers.

(b) Amounts do not sum across due to deferred tax adjustments recorded at the Exelon Corporation parent company, primarily related to certain employee compensation plans.

(c) Given the regulatory treatment of income tax benefits related to electric and gas distribution repairs, PECO remained in an overall net regulatory asset position as of December 31, 2017 after recording the impacts related to the TCJA.

ScheduleOfCategorizationOfNetRegulatoryLiabilitiesDueToTaxReform [Table Text Block]

The table below sets forth the Registrants’ estimated categorization of their net regulatory liabilities as of December 31, 2017. The amounts in the table below are shown on an after-tax basis reflecting future net cash outflows after taking into consideration the income tax benefits associated with the ultimate settlement with customers.

					Successor
	Exelon	ComEd	PECO(a)	BGE	PHI	PEPCO	DPL	ACE
Subject to IRS Normalization Rules	$3,040	$1,400	$533	$459	$648	$299	$195	$153
Subject to Rate Regulator Determination	1,694	573	43	324	754	391	194	170
Net Regulatory Liabilities	$4,734	$1,973	$576	$783	$1,402	$690	$389	$	323

_________

(a) Given the regulatory treatment of income tax benefits related to electric and gas distribution repairs, PECO was in an overall net regulatory asset position as of December 31, 2017 after recording the impacts related to the TCJA. As a result, the amount of customer benefits resulting from the TCJA subject to the discretion of PECO's rate regulators are lower relative to the other Utility Registrants.

Schedule of Components of Income Tax Expense (Benefit)

Income tax expense (benefit) from continuing operations is comprised of the following components:

	For the Year Ended December 31, 2018
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Included in operations:
Federal
Current	$	226		$	337		$	(63	)	$	11		$	(5	)	$	(4	)	$	28		$	(3	)	$	(14	)
Deferred	(98		)	(347		)	145			10			47			24			(21		)	13			18
Investment tax credit amortization	(24		)	(21		)	(2		)	—			—			(1		)	—			—			—
State
Current	(1		)	6			(29		)	1			—			7			—			—			—
Deferred	17			(83		)	117			(16		)	32			9			6			12			8
Total	$	120		$	(108	)	$	168		$	6		$	74		$	35		$	13		$	22		$	12

	For the Year Ended December 31, 2017(a)
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Included in operations:
Federal
Current	$	194		$	584		$	(191	)	$	71		$	74		$	(60	)	$	(20	)	$	(24	)	$	(12	)
Deferred	(471		)	(2,005		)	523			28			101			250			114			82			34
Investment tax credit amortization	(25		)	(21		)	(2		)	—			(1		)	(1		)	—			—			—
State
Current	14			65			(49		)	14			(5		)	(4		)	(2		)	—			—
Deferred	162			1			136			(9		)	49			32			13			13			4
Total	$	(126	)	$	(1,376	)	$	417		$	104		$	218		$	217		$	105		$	71		$	26

																								Successor			Predecessor
	For the Year Ended December 31, 2016(a)																							March 24, 2016 to December 31, 2016			January 1, 2016 to March 23, 2016
	Exelon			Generation			ComEd			PECO		BGE			Pepco			DPL			ACE			PHI			PHI
Included in operations:
Federal
Current	$	60		$	513		$	(135	)	$	63	$	51		$	(118	)	$	(88	)	$	(26	)	$	(281	)	$	—
Deferred	600			(254		)	379			72		88			136			97			22			283			10
Investment tax credit amortization	(24		)	(20		)	(2		)	—		(1		)	—			—			—			(1		)	—
State
Current	39			45			(4		)	9		5			7			1			—			(11		)	—
Deferred	78			(2		)	63			5		31			16			12			—			13			7
Total	$	753		$	282		$	301		$	149	$	174		$	41		$	22		$	(4	)	$	3		$	17

The following tables represent the net interest and penalties receivable (payable), including interest and penalties related to tax positions reflected in the Registrants’ Consolidated Balance Sheets.

Net interest receivable (payable) as of	Exelon		Generation			ComEd		PECO		BGE		PHI		Pepco		DPL		ACE
December 31, 2018	$	236	$	(2	)	$	4	$	—	$	—	$	1	$	—	$	—	$	—
December 31, 2017	233		(3		)	4		—		—		2		—		—		—

Net penalties payable as of	Exelon			Generation		ComEd		PECO		BGE		PHI		Pepco		DPL		ACE
December 31, 2018	$	(17	)	$	—	$	—	$	—	$	—	$	—	$	—	$	—	$	—
December 31, 2017	(17		)	—		—		—		—		—		—		—		—

Effective Income Tax Rate Reconciliation

The effective income tax rate from continuing operations varies from the U.S. federal statutory rate principally due to the following:

	For the Year Ended December 31, 2018
											Successor
	Exelon		Generation		ComEd		PECO		BGE		PHI		Pepco		DPL		ACE
U.S. Federal statutory rate	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%	21.0	%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	0.6		(16.6	)	8.3		(2.6	)	6.6		3.0		2.2		6.7		7.4
Qualified NDT fund income	(1.9	)	(11.8	)	—		—		—		—		—		—		—
Amortization of investment tax credit, including deferred taxes on basis difference	(1.2	)	(6.5	)	(0.2	)	(0.1	)	(0.1	)	(0.2	)	(0.1	)	(0.3	)	(0.4	)
Plant basis differences	(3.5	)	—		(0.2	)	(14.1	)	(1.3	)	(1.6	)	(2.7	)	(0.3	)	(0.5	)
Production tax credits and other credits	(2.2	)	(13.5	)	—		—		—		—		—		—		—
Noncontrolling interests	(1.0	)	(6.1	)	—		—		—		—		—		—		—
Excess deferred tax amortization	(8.3	)	—		(9.1	)	(3.2	)	(8.0	)	(14.5	)	(14.8	)	(12.0	)	(14.9	)
Tax Cuts and Jobs Act of 2017	0.9		2.7		(0.1	)	—		—		0.1		—		—		—
Other	1.0		1.3		0.5		0.3		0.9		0.3		0.2		0.4		1.2
Effective income tax rate	5.4	%	(29.5	)%	20.2	%	1.3	%	19.1	%	8.1	%	5.8	%	15.5	%	13.8	%

	For the Year Ended December 31, 2017(a)
											Successor
	Exelon		Generation		ComEd		PECO		BGE		PHI		Pepco		DPL		ACE
U.S. Federal statutory rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	2.3		2.9		5.7		0.6		5.4		4.8		3.2		5.4		5.6
Qualified NDT fund income	3.8		9.9		—		—		—		—		—		—		—
Amortization of investment tax credit, including deferred taxes on basis difference	(0.9	)	(2.1	)	(0.2	)	(0.1	)	(0.1	)	(0.2	)	(0.1	)	(0.2	)	(0.4	)
Plant basis differences(b)	(1.7	)	—		0.3		(13.8	)	0.1		1.1		(0.4	)	2.0		3.6
Production tax credits and other credits	(1.8	)	(4.7	)	—		—		—		—		—		—		—
Like-kind exchange	(1.2	)	—		1.3		—		—		—		—		—		—
Merger expenses	(3.6	)	(1.2	)	—		—		—		(9.5	)	(6.3	)	(7.8	)	(19.8	)
FitzPatrick bargain purchase gain	(2.2	)	(5.6	)	—		—		—		—		—		—		—
Tax Cuts and Jobs Act of 2017(c)	(33.1	)	(128.3	)	0.1		(2.3	)	0.9		6.4		2.7		2.5		1.6
Other	0.1		(0.5	)	0.2		(0.1	)	0.2		(0.1	)	(0.2	)	0.1		(0.4	)
Effective income tax rate	(3.3	)%	(94.6	)%	42.4	%	19.3	%	41.5	%	37.5	%	33.9	%	37.0	%	25.2	%

																	Successor		Predecessor
	For the Year Ended December 31, 2016(a)																March 24, 2016 to December 31, 2016		January 1, 2016 to March 23, 2016
	Exelon		Generation		ComEd		PECO		BGE		Pepco		DPL (d)		ACE (d)		PHI (d)		PHI
U.S. Federal statutory rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit (e)	3.3		3.2		5.6		1.3		5.0		15.7		52.7		6.2		5.8		11.9
Qualified NDT fund income	3.4		7.9		—		—		—		—		—		—		—		—
Amortization of investment tax credit, including deferred taxes on basis difference	(1.2	)	(2.3	)	(0.3	)	(0.1	)	(0.1	)	(0.2	)	(3.7	)	0.8		1.4		(0.9	)
Plant basis differences	(4.9	)	—		(0.6	)	(9.6	)	(2.7	)	(22.8	)	(25.5	)	10.3		39.0		(13.5	)
Production tax credits and other credits	(3.6	)	(8.3	)	—		—		—		—		—		—		—		—
Noncontrolling interests	(0.2	)	(0.6	)	—		—		—		—		—		—		—		—
Statute of limitations expiration	(0.4	)	(1.7	)	—		—		—		—		—		—		—		—
Penalties	1.9		—		4.5		—		—		—		—		—		(0.7	)	—
Merger Expenses	5.6		1.1		—		—		—		23.5		112.9		(44.9	)	(89.0	)	11.1
Other (f)	(0.7	)	(1.4	)	0.1		(1.2	)	—		(1.8	)	(2.2	)	1.3		3.3		3.6
Effective income tax rate	38.2	%	32.9	%	44.3	%	25.4	%	37.2	%	49.4	%	169.2	%	8.7	%	(5.2	)%	47.2	%

__________

(a) Exelon retrospectively adopted the new standard Revenue from Contracts with Customers. The standard was adopted as of January 1, 2018. The effective income tax rates are recast to reflect the impact of the new standard.

(b) Includes the charges related to the transmission-related income tax regulatory asset for Exelon, ComEd, BGE, PHI, Pepco, DPL and ACE of $35 million, $3 million, $5 million, $27 million, $14 million, $6 million and $7 million, respectively. See Note 4 - Regulatory Matters for additional information.

(c) Included are impacts for TCJA other than the corporate rate change, including revisions further limiting tax deductions for compensation of certain highest paid executives, the write-off of foreign tax credit carryforwards, and loss of a 2015 domestic production activities deduction due to an NOL carryback.

(d) DPL and ACE recognized a loss before income taxes for the year ended December 31, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through December 31, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.

(e) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.

(f) At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. The method change request was filed and accepted in 2017. No change to the results recorded as of December 31, 2016.

Tax Effects of Temporary Differences

Tax Differences and Carryforwards

The tax effects of temporary differences and carryforwards, which give rise to significant portions of the deferred tax assets (liabilities), as of December 31, 2018 and 2017 are presented below:

	As of December 31, 2018
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Plant basis differences	$	(12,533	)	$	(2,495	)	$	(4,059	)	$	(1,862	)	$	(1,399	)	$	(2,577	)	$	(1,148	)	$	(743	)	$	(645	)
Accrual based contracts	117			(44		)	—			—			—			161			—			—			—
Derivatives and other financial instruments	89			35			69			—			—			3			—			—			—
Deferred pension and postretirement obligation	1,435			(188		)	(255		)	(26		)	(26		)	(102		)	(78		)	(46		)	(14		)
Nuclear decommissioning activities	(351		)	(351		)	—			—			—			—			—			—			—
Deferred debt refinancing costs	234			23			(7		)	—			(3		)	187			(4		)	(2		)	(1		)
Regulatory assets and liabilities	(749		)	—			300			(129		)	172			(90		)	58			96			83
Tax loss carryforward	237			78			—			18			25			96			12			52			26
Tax credit carryforward	811			816			—			—			—			—			—			—			—
Investment in partnerships	(797		)	(775		)	—			—			—			—			—			—			—
Other, net	934			239			151			67			12			196			98			17			19
Deferred income tax liabilities (net)	$	(10,573	)	$	(2,662	)	$	(3,801	)	$	(1,932	)	$	(1,219	)	$	(2,126	)	$	(1,062	)	$	(626	)	$	(532	)
Unamortized investment tax credits	(724		)	(700		)	(12		)	(1		)	(3		)	(8		)	(2		)	(2		)	(3		)
Total deferred income tax liabilities (net) and unamortized investment tax credits	$	(11,297	)	$	(3,362	)	$	(3,813	)	$	(1,933	)	$	(1,222	)	$	(2,134	)	$	(1,064	)	$	(628	)	$	(535	)

	As of December 31, 2017 (a)
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Plant basis differences	$	(12,490	)	$	(2,819	)	$	(3,825	)	$	(1,762	)	$	(1,368	)	$	(2,521	)	$	(1,152	)	$	(717	)	$	(607	)
Accrual based contracts	150			(66		)	—			—			—			216			—			—			—
Derivatives and other financial instruments	(85		)	(66		)	(2		)	—			—			3			—			—			—
Deferred pension and postretirement obligation	1,463			(205		)	(285		)	(15		)	(29		)	(130		)	(78		)	(51		)	(18		)
Nuclear decommissioning activities	(553		)	(553		)	—			—			—			—			—			—			—
Deferred debt refinancing costs	217			26			(8		)	(1		)	(3		)	203			(4		)	(2		)	(1		)
Regulatory assets and liabilities	(688		)	—			489			(90		)	136			(184		)	39			88			86
Tax loss carryforward	344			76			33			9			11			156			40			68			35
Tax credit carryforward	861			868			1			—			—			6			—			—			—
Investment in partnerships	(434		)	(416		)	—			—			—			—			—			—			—
Other, net	746			78			141			71			13			193			94			14			16
Deferred income tax liabilities (net)	$	(10,469	)	$	(3,077	)	$	(3,456	)	$	(1,788	)	$	(1,240	)	$	(2,058	)	$	(1,061	)	$	(600	)	$	(489	)
Unamortized investment tax credits	(732		)	(705		)	(13		)	(1		)	(4		)	(8		)	(2		)	(3		)	(4		)
Total deferred income tax liabilities (net) and unamortized investment tax credits	$	(11,201	)	$	(3,782	)	$	(3,469	)	$	(1,789	)	$	(1,244	)	$	(2,066	)	$	(1,063	)	$	(603	)	$	(493	)

Summary of Loss Carryforwards

	As of December 31, 2018
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Plant basis differences	$	(12,533	)	$	(2,495	)	$	(4,059	)	$	(1,862	)	$	(1,399	)	$	(2,577	)	$	(1,148	)	$	(743	)	$	(645	)
Accrual based contracts	117			(44		)	—			—			—			161			—			—			—
Derivatives and other financial instruments	89			35			69			—			—			3			—			—			—
Deferred pension and postretirement obligation	1,435			(188		)	(255		)	(26		)	(26		)	(102		)	(78		)	(46		)	(14		)
Nuclear decommissioning activities	(351		)	(351		)	—			—			—			—			—			—			—
Deferred debt refinancing costs	234			23			(7		)	—			(3		)	187			(4		)	(2		)	(1		)
Regulatory assets and liabilities	(749		)	—			300			(129		)	172			(90		)	58			96			83
Tax loss carryforward	237			78			—			18			25			96			12			52			26
Tax credit carryforward	811			816			—			—			—			—			—			—			—
Investment in partnerships	(797		)	(775		)	—			—			—			—			—			—			—
Other, net	934			239			151			67			12			196			98			17			19
Deferred income tax liabilities (net)	$	(10,573	)	$	(2,662	)	$	(3,801	)	$	(1,932	)	$	(1,219	)	$	(2,126	)	$	(1,062	)	$	(626	)	$	(532	)
Unamortized investment tax credits	(724		)	(700		)	(12		)	(1		)	(3		)	(8		)	(2		)	(2		)	(3		)
Total deferred income tax liabilities (net) and unamortized investment tax credits	$	(11,297	)	$	(3,362	)	$	(3,813	)	$	(1,933	)	$	(1,222	)	$	(2,134	)	$	(1,064	)	$	(628	)	$	(535	)

	As of December 31, 2017 (a)
																Successor
	Exelon			Generation			ComEd			PECO			BGE			PHI			Pepco			DPL			ACE
Plant basis differences	$	(12,490	)	$	(2,819	)	$	(3,825	)	$	(1,762	)	$	(1,368	)	$	(2,521	)	$	(1,152	)	$	(717	)	$	(607	)
Accrual based contracts	150			(66		)	—			—			—			216			—			—			—
Derivatives and other financial instruments	(85		)	(66		)	(2		)	—			—			3			—			—			—
Deferred pension and postretirement obligation	1,463			(205		)	(285		)	(15		)	(29		)	(130		)	(78		)	(51		)	(18		)
Nuclear decommissioning activities	(553		)	(553		)	—			—			—			—			—			—			—
Deferred debt refinancing costs	217			26			(8		)	(1		)	(3		)	203			(4		)	(2		)	(1		)
Regulatory assets and liabilities	(688		)	—			489			(90		)	136			(184		)	39			88			86
Tax loss carryforward	344			76			33			9			11			156			40			68			35
Tax credit carryforward	861			868			1			—			—			6			—			—			—
Investment in partnerships	(434		)	(416		)	—			—			—			—			—			—			—
Other, net	746			78			141			71			13			193			94			14			16
Deferred income tax liabilities (net)	$	(10,469	)	$	(3,077	)	$	(3,456	)	$	(1,788	)	$	(1,240	)	$	(2,058	)	$	(1,061	)	$	(600	)	$	(489	)
Unamortized investment tax credits	(732		)	(705		)	(13		)	(1		)	(4		)	(8		)	(2		)	(3		)	(4		)
Total deferred income tax liabilities (net) and unamortized investment tax credits	$	(11,201	)	$	(3,782	)	$	(3,469	)	$	(1,789	)	$	(1,244	)	$	(2,066	)	$	(1,063	)	$	(603	)	$	(493	)

__________

(a) Includes remeasurement impacts related to the TCJA.

The following table provides the Registrants’ carryforwards and any corresponding valuation allowances as of December 31, 2018:

										Successor
	Exelon		Generation		ComEd	PECO		BGE		PHI		Pepco		DPL		ACE
Federal
Federal general business credits carryforwards	811	(a)	816		—	—		—		—		—		—		—
State
State net operating losses	4,103	(b)	1,544	(b)	—	224	(c)	395	(d)	1,492	(e)	192	(f)	772	(g)	365	(h)
Deferred taxes on state tax attributes (net)	272		104		—	18		26		102		12		52		26
Valuation allowance on state tax attributes	35		26		—	—		1		6		—		—		—

__________

(a) Exelon’s federal general business credit carryforwards will begin expiring in 2033.

(b) Exelon’s and Generation's state net operating losses and credit carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2019.

(c) PECO's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2031.

(d) BGE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2026.

(e) PHI's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2036.

(f) Pepco's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2033.

(g) DPL's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2030.

(h) ACE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2031.

Reconciliation of Unrecognized Tax Benefits Excluding Amounts Pertaining to Examined Tax Returns Foll Forward

The following tables provide a reconciliation of the Registrants’ unrecognized tax benefits as of December 31, 2018, 2017 and 2016:

	Exelon			Generation			ComEd		PECO		BGE			PHI			Pepco			DPL			ACE
Unrecognized tax benefits at January 1, 2018	$	743		$	468		$	2	$	—	$	120		$	125		$	59		$	21		$	14
Change to positions that only affect timing	15			15			—		—		—			—			—			—			—
Increases based on tax positions prior to 2018	30			21			—		—		—			8			7			1			—
Decreases based on tax positions prior to 2018	(251		)	(36		)	—		—		(120		)	(88		)	(66		)	(22		)	—
Decrease from settlements with taxing authorities	(53		)	(53		)	—		—		—			—			—			—			—
Decreases from expiration of statute of limitations	(7		)	(7		)	—		—		—			—			—			—			—
Unrecognized tax benefits at December 31, 2018	$	477		$	408		$	2	$	—	$	—		$	45		$	—		$	—		$	14

	Exelon			Generation			ComEd			PECO		BGE		PHI			Pepco			DPL			ACE
Unrecognized tax benefits at January 1, 2017	$	916		$	490		$	(12	)	$	—	$	120	$	172		$	80		$	37		$	22
Increases based on tax positions prior to 2017	28			—			14			—		—		14			—			—			14
Decreases based on tax positions prior to 2017	(196		)	(17		)	—			—		—		(61		)	(21		)	(16		)	(22		)
Decrease from settlements with taxing authorities	(5		)	(5		)	—			—		—		—			—			—			—
Unrecognized tax benefits at December 31, 2017	$	743		$	468		$	2		$	—	$	120	$	125		$	59		$	21		$	14

	Exelon			Generation			ComEd			PECO		BGE		PHI			Pepco		DPL		ACE
Unrecognized tax benefits at January 1, 2016	$	1,078		$	534		$	142		$	—	$	120	$	22		$	8	$	3	$	—
Merger balance transfer	22			5			—			—		—		(5		)	—		—		—
Increases based on tax positions related to 2016	108			10			—			—		—		59			21		16		22
Change to positions that only affect timing	(332		)	(12		)	(154		)	—		—		—			—		—		—
Increases based on tax positions prior to 2016	88			—			—			—		—		96			51		18		—
Decreases based on tax positions prior to 2016	(21		)	(20		)	—			—		—		—			—		—		—
Decreases from settlements with taxing authorities	(27		)	(27		)	—			—		—		—			—		—		—
Unrecognized tax benefits at December 31, 2016	$	916		$	490		$	(12	)	$	—	$	120	$	172		$	80	$	37	$	22

Interest Income and Interest Expense Disclosure [Table Text Block]

The following tables set forth the net interest and penalty expense, including interest and penalties related to tax positions, recognized in Interest expense, net and Other, net in Other income and deductions in the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

Net interest expense (income) for the years ended	Exelon			Generation			ComEd		PECO		BGE		Pepco		DPL		ACE
December 31, 2018	$	(3	)	$	—		$	—	$	—	$	—	$	—	$	—	$	—
December 31, 2017	37			(1		)	11		—		—		—		—		—
December 31, 2016	165			(13		)	117		—		—		6		—		(1		)

Net penalty expense (income) for the years ended	Exelon			Generation		ComEd		PECO		BGE		Pepco		DPL		ACE
December 31, 2018	$	—		$	—	$	—	$	—	$	—	$	—	$	—	$	—
December 31, 2017	(2		)	—		—		—		—		—		—		—
December 31, 2016	106			—		86		—		—		—		—		—

	Successor							Predecessor
PHI	December 31, 2018		December 31, 2017		March 24, 2016 to December 31, 2016			January 1, 2016 to March 23, 2016
Net interest expense	$	—	$	—	$	(2	)	$	—

Summary of Open Tax Years by Jurisdiction

Description of tax years open to assessment by major jurisdiction

Taxpayer	Open Years
Exelon (and predecessors) and subsidiaries consolidated federal income tax returns	1999, 2001-2017
PHI Holdings and subsidiaries consolidated federal income tax returns	2013, 2015-2016
Exelon and subsidiaries Illinois unitary income tax returns	2010-2017
Constellation combined New York corporate income tax returns	2010-March 2012
Exelon combined New York corporate income tax returns	2011-2017
Exelon New Jersey corporate income tax returns	2013-2017
Exelon Pennsylvania corporate net income tax returns	2011-2017
PECO Pennsylvania separate company returns	2015-2017
DPL Delaware separate company returns	Same as federal
ACE New Jersey separate company returns	2014-2017
Exelon and subsidiaries District of Columbia corporate income tax returns	2015-2017
PHI Holdings and subsidiaries District of Columbia corporate income tax returns	2015-2016
Various separate company Maryland corporate net income tax returns	Same as federal