Income Taxes (Details) (USD $)	3 Months Ended				9 Months Ended	12 Months Ended
	Dec. 31, 2012		Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2012	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[1]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						(3.60%)	[1]	4.40%	3.00%
Qualified nuclear decommissioning trust fund income (losses)						5.40%	[1]	0.50%	1.70%
Domestic production activities deduction								(0.30%)	(1.20%)
Tax exempt income						(0.20%)	[1]	(0.20%)	(0.10%)
Nontaxable postretirement benefits								(0.30%)
Health Care Reform Legislation						0.10%	[1]	(0.20%)	1.40%
Amortization of investment tax credit						(1.10%)	[1]	0.90%	(0.30%)
Plant basis differences						(2.40%)	[1]	(1.00%)
Production Tax Credits						(2.20%)	[1]
Fines and Penalties						(2.60%)	[1]
Merger Expenses						(2.40%)	[1],[2]
Other						(1.10%)	[1]	(0.20%)	(0.20%)
Effective income tax rate						34.90%	[1]	36.80%	39.30%
Unrecognized Tax Benefits For Which Timing Of Ultimate Benefits Uncertain [Abstract]
Tax positions for which there is uncertainty about the timing of tax benefits	$ 730,000,000					$ 730,000,000		$ 804,000,000
Accounting for Uncertainty in Income Taxes [Abstract]
Unrecognized tax benefits that if recognized would affect the effective tax rate	294,000,000					294,000,000		3,000,000
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions	31,000,000					31,000,000		74,000,000
Net interest (income) expense recognized related to uncertain tax positions						(1,000,000)		(56,000,000)	110,000,000
Tax Method of Accounting for Repairs [Abstract]
Repair cost tax benefit					26,000,000
1999 Sale of Fossil Generating Assets [Abstract]
Deferred tax gain on sale of fossil generating assets	2,800,000,000					2,800,000,000
Deferred tax gain under involuntary conversion provisions of the IRC	1,600,000,000					1,600,000,000
Deferred tax gain under like-kind exchange provisions of the IRC	1,200,000,000					1,200,000,000
IRS asserted penalties for understatement of tax						86,000,000
Potential tax and interest from a successful IRS challenge of the like-kind exchange transaction position	860,000,000					860,000,000
Potential interest expense from a successful IRS challenge of the like-kind exchange position	320,000,000					320,000,000
Unsuccessful Litigation Determinations [Abstract]
Expected non-cash charge to earnings	270,000,000					270,000,000
Unrecognized tax benefits for Generation Repairs	107,000,000					107,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									65,000,000
Tax Settlement [Abstract]
Payment to IRS for open tax positions								302,000,000	302,000,000
Income tax benefit recorded as a result of re-apportionment of state income taxes [Abstract]
Income tax benefit recorded as a result of re-apportionment of state income taxes	3,000,000		116,000,000	22,000,000				1,000,000
Gross Deferred Income tax expense recorded as a result of re-apportionment of state income taxes			72,000,000
Deferred state tax liability resulting from purchase accounting			44,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction						300,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			807,000,000	787,000,000	807,000,000	807,000,000		787,000,000	1,498,000,000
Merger Balance Transfer						195,000,000
Increases based on tax positions related to current year						34,000,000		5,000,000	1,000,000
Decreases based on tax positions related to current year									(2,000,000)
Changes to tax positions that only affect timing						(88,000,000)		21,000,000	(262,000,000)
Increases based on tax positions prior to current year						(91,000,000)			8,000,000
Decreases based on tax positions prior to current year						6,000,000		(3,000,000)	3,000,000
Decreases related to settlements with taxing authorities						2,000,000			(452,000,000)
Decreases from expiration of statute of limitations						(7,000,000)		(3,000,000)	(1,000,000)
Unrecognized tax benefits - ending balance	1,024,000,000					1,024,000,000		807,000,000	787,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						627,000,000		1,457,000,000	1,658,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss	635,000,000	[3]				635,000,000	[3]
Federal capital loss carryforward	178,000,000	[4]				178,000,000	[4]
Federal general business credits carryforward						226,000,000	[5]
State net operating loss carryforward	3,365,000,000	[6]				3,365,000,000	[6]
State capital loss carryforward	127,000,000	[7]				127,000,000	[7]
Deferred taxes	187,000,000					187,000,000
Valuation allowance	36,000,000					36,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences	(10,689,000,000)					(10,689,000,000)		(7,803,000,000)
Accrual based contracts	(389,000,000)					(389,000,000)
Unrealized gains on derivative financial instruments	(392,000,000)					(392,000,000)		(468,000,000)
Deferred pension and other post-retirement obligation	1,225,000,000					1,225,000,000		665,000,000
Nuclear decommissioning activities	(604,000,000)					(604,000,000)		(452,000,000)
Deferred debt refinancing costs	(537,000,000)					(537,000,000)		(37,000,000)
Net operating losses	421,000,000					421,000,000
Tax credit carry-forward	226,000,000					226,000,000
Investment in CENG	(405,000,000)					(405,000,000)
Other, net	(25,000,000)					(25,000,000)		41,000,000
Deferred income tax liabilities, net	(11,169,000,000)					(11,169,000,000)		(8,054,000,000)
Unamortized investment tax credits	(251,000,000)					(251,000,000)		(200,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits	(11,420,000,000)					(11,420,000,000)		(8,254,000,000)
Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						37,000,000		1,000,000	506,000,000
Deferred Income Tax Expense Benefit						701,000,000		1,200,000,000	972,000,000
Investment tax credit amortization						(11,000,000)		(12,000,000)	(12,000,000)
State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						(25,000,000)		(3,000,000)	171,000,000
Deferred Income Tax Expense Benefit						(75,000,000)		271,000,000	21,000,000
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[1]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						4.70%	[1]	4.50%	3.70%
Qualified nuclear decommissioning trust fund income (losses)						9.10%	[1]	0.70%	2.30%
Domestic production activities deduction								(0.40%)	(1.50%)
Tax exempt income						(0.40%)	[1]	(0.20%)	(0.20%)
Nontaxable postretirement benefits								(0.30%)
Health Care Reform Legislation									0.70%
Amortization of investment tax credit						(1.30%)	[1]	1.20%	(0.20%)
Production Tax Credits						(3.70%)	[1]
Uncertain Tax Position Remeasurement									(2.00%)
Fines and Penalties						(4.40%)	[1]
Other						(0.50%)	[1]	(0.70%)	(0.40%)
Effective income tax rate						47.30%	[1]	37.40%	37.40%
Accounting for Uncertainty in Income Taxes [Abstract]
Unrecognized tax benefits that if recognized would affect the effective tax rate	263,000,000					263,000,000		3,000,000
Information by nature of uncertainty related to unrecognized tax benefits	100,000,000					100,000,000
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions	(20,000,000)					(20,000,000)		33,000,000
Net interest (income) expense recognized related to uncertain tax positions						11,000,000		(40,000,000)	6,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Current Tax Expense (Benefit)									(70,000,000)
Income tax benefit recorded as a result of re-apportionment of state income taxes [Abstract]
Income tax benefit recorded as a result of re-apportionment of state income taxes	7,000,000		14,000,000	11,000,000				8,000,000
Deferred state tax liability resulting from purchase accounting			14,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Income tax benefit (expense) as a result of repair costs deduction						28,000,000
Cash tax benefit (detriment) as a result of repair costs deduction						28,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits						48,000,000		30,000,000	60,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			683,000,000	664,000,000	683,000,000	683,000,000		664,000,000	633,000,000
Merger Balance Transfer						183,000,000
Increases based on tax positions related to current year						3,000,000		1,000,000
Decreases based on tax positions related to current year									(2,000,000)
Changes to tax positions that only affect timing						(69,000,000)		24,000,000	55,000,000
Increases based on tax positions prior to current year						(91,000,000)			8,000,000
Decreases based on tax positions prior to current year						6,000,000		(3,000,000)	3,000,000
Decreases related to settlements with taxing authorities						2,000,000			(26,000,000)
Decreases from expiration of statute of limitations						(7,000,000)		(3,000,000)	(1,000,000)
Unrecognized tax benefits - ending balance	876,000,000					876,000,000		683,000,000	664,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						500,000,000		1,056,000,000	1,178,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss	303,000,000					303,000,000
Federal capital loss carryforward	178,000,000					178,000,000
Federal general business credits carryforward						226,000,000
State net operating loss carryforward	1,649,000,000	[8]				1,649,000,000	[8]
State capital loss carryforward	119,000,000	[9]				119,000,000	[9]
Deferred taxes	99,000,000					99,000,000
Valuation allowance	35,000,000					35,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences	(3,545,000,000)					(3,545,000,000)		(2,670,000,000)
Accrual based contracts	(389,000,000)					(389,000,000)
Unrealized gains on derivative financial instruments	(479,000,000)					(479,000,000)		(737,000,000)
Deferred pension and other post-retirement obligation	(439,000,000)					(439,000,000)		(520,000,000)
Nuclear decommissioning activities	(604,000,000)					(604,000,000)		(452,000,000)
Deferred debt refinancing costs	163,000,000					163,000,000
Net operating losses	226,000,000					226,000,000
Tax credit carry-forward	226,000,000					226,000,000
Investment in CENG	(419,000,000)					(419,000,000)
Other, net	9,000,000					9,000,000		338,000,000
Deferred income tax liabilities, net	(5,251,000,000)					(5,251,000,000)		(4,041,000,000)
Unamortized investment tax credits	(216,000,000)					(216,000,000)		(169,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits	(5,467,000,000)					(5,467,000,000)		(4,210,000,000)
Exelon Generation Co L L C [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						104,000,000		431,000,000	372,000,000
Deferred Income Tax Expense Benefit						326,000,000		435,000,000	635,000,000
Investment tax credit amortization						(6,000,000)		(7,000,000)	(7,000,000)
Exelon Generation Co L L C [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						(12,000,000)		74,000,000	65,000,000
Deferred Income Tax Expense Benefit						88,000,000		123,000,000	113,000,000
Exelon Generation Co L L C [Member] | Settlement With Taxing Authority [Member]
Accounting for Uncertainty in Income Taxes [Abstract]
Information by nature of uncertainty related to unrecognized tax benefits	55,000,000					55,000,000
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%		35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						4.60%		3.60%	6.30%
Nontaxable postretirement benefits								(0.40%)
Health Care Reform Legislation						0.40%		(1.00%)	1.40%
Amortization of investment tax credit						(0.40%)			(0.40%)
Plant basis differences						(0.30%)		(0.30%)	(0.10%)
Uncertain Tax Position Remeasurement									9.00%
Other						(0.60%)		0.60%	0.20%
Effective income tax rate						38.70%		37.50%	51.40%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions	107,000,000					107,000,000		23,000,000
Net interest (income) expense recognized related to uncertain tax positions						(20,000,000)		(14,000,000)	57,000,000
Unsuccessful Litigation Determinations [Abstract]
Expected non-cash charge to earnings	185,000,000					185,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									36,000,000
FIN 48 Tax Remeasurement Current Tax Expense (Benefit)									70,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction						250,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits									2,000,000
Intercompany Non-Cash Allocation of Tax Benefit									11,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			70,000,000	72,000,000	70,000,000	70,000,000		72,000,000	471,000,000
Changes to tax positions that only affect timing						(3,000,000)		(2,000,000)	(3,000,000)
Decreases related to settlements with taxing authorities									(396,000,000)
Unrecognized tax benefits - ending balance	67,000,000					67,000,000		70,000,000	72,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						239,000,000		250,000,000	357,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss	91,000,000					91,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences	(3,537,000,000)					(3,537,000,000)		(3,264,000,000)
Unrealized gains on derivative financial instruments	(4,000,000)					(4,000,000)		(4,000,000)
Deferred pension and other post-retirement obligation	(598,000,000)					(598,000,000)		(623,000,000)
Deferred debt refinancing costs	(25,000,000)					(25,000,000)		(31,000,000)
Net operating losses	32,000,000					32,000,000
Other, net	(33,000,000)					(33,000,000)		16,000,000
Deferred income tax liabilities, net	(4,165,000,000)					(4,165,000,000)		(3,906,000,000)
Unamortized investment tax credits	(24,000,000)					(24,000,000)		(26,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits	(4,189,000,000)					(4,189,000,000)		(3,932,000,000)
Commonwealth Edison Co [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						(40,000,000)		(329,000,000)	(203,000,000)
Deferred Income Tax Expense Benefit						237,000,000		544,000,000	496,000,000
Investment tax credit amortization						(2,000,000)		(3,000,000)	(3,000,000)
Commonwealth Edison Co [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						6,000,000		(123,000,000)	(22,000,000)
Deferred Income Tax Expense Benefit						38,000,000		161,000,000	89,000,000
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%		35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						2.00%		(0.50%)	(4.70%)
Nontaxable postretirement benefits								(0.30%)
Health Care Reform Legislation									1.60%
Amortization of investment tax credit						(0.30%)			(0.40%)
Plant basis differences						(11.50%)		(6.90%)	0.20%
Other						(0.20%)			0.20%
Effective income tax rate						25.00%		27.30%	31.90%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions	2,000,000					2,000,000		28,000,000
Net interest (income) expense recognized related to uncertain tax positions						(1,000,000)		(1,000,000)	35,000,000
Tax Method of Accounting for Repairs [Abstract]
Repair cost tax benefit					29,000,000
FIN 48 Tax Remeasurement [Abstract]
FIN 48 Tax Remeasurement Interest Expense									22,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Income tax benefit (expense) as a result of repair costs deduction						35,000,000
Cash tax benefit (detriment) as a result of repair costs deduction						95,000,000
Allocated tax benefits [Abstract]
Allocated tax benefits						9,000,000		18,000,000	43,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			48,000,000	44,000,000	48,000,000	48,000,000		44,000,000	372,000,000
Increases based on tax positions related to current year								4,000,000
Changes to tax positions that only affect timing						(4,000,000)			(328,000,000)
Unrecognized tax benefits - ending balance	44,000,000					44,000,000		48,000,000	44,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						127,000,000		146,000,000	152,000,000
Operating Loss Carryforwards [Line Items]
State net operating loss carryforward	209,000,000	[10]				209,000,000	[10]
Deferred taxes	14,000,000					14,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences	(2,437,000,000)					(2,437,000,000)		(2,238,000,000)
Deferred pension and other post-retirement obligation	(11,000,000)					(11,000,000)		(31,000,000)
Deferred debt refinancing costs	(4,000,000)					(4,000,000)		(6,000,000)
Net operating losses	14,000,000					14,000,000
Other, net	150,000,000					150,000,000		135,000,000
Deferred income tax liabilities, net	(2,288,000,000)					(2,288,000,000)		(2,140,000,000)
Unamortized investment tax credits	(3,000,000)					(3,000,000)		(5,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits	(2,291,000,000)					(2,291,000,000)		(2,145,000,000)
PECO Energy Co [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						88,000,000		(71,000,000)	464,000,000
Deferred Income Tax Expense Benefit						25,000,000		223,000,000	(276,000,000)
Investment tax credit amortization						(2,000,000)		(2,000,000)	(2,000,000)
PECO Energy Co [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						4,000,000		(37,000,000)	87,000,000
Deferred Income Tax Expense Benefit						12,000,000		33,000,000	(121,000,000)
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation
U.S. Federal statutory rate						35.00%	[11]	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit						24.30%	[11]	5.20%	5.50%
Health Care Reform Legislation						11.60%	[11]	(0.50%)	1.10%
Amortization of investment tax credit						(8.60%)	[11]	(0.50%)	(0.40%)
Plant basis differences						(9.00%)	[11]	(2.00%)	(1.00%)
Merger Expenses						(24.20%)	[11],[2]
Other						(13.90%)	[11]	(1.70%)	(0.40%)
Effective income tax rate						63.60%	[11]	35.50%	39.80%
Interest recognized related to uncertain tax positions [Abstract]
Net interest receivable (payable) recognized related to uncertain tax positions								(1,000,000)
Net interest (income) expense recognized related to uncertain tax positions								(3,000,000)	2,000,000
Income and cash tax benefit as a result of repair costs deduction [Abstract]
Cash tax benefit (detriment) as a result of repair costs deduction						27,000,000
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance			11,000,000	73,000,000	11,000,000	11,000,000		73,000,000	112,000,000
Merger Balance Transfer						0
Changes to tax positions that only affect timing						(11,000,000)		(62,000,000)	(39,000,000)
Unrecognized tax benefits - ending balance								11,000,000	73,000,000
Income Tax Expense Benefit Continuing Operations [Line Items]
Income Tax Expense (Benefit)						7,000,000		75,000,000	97,000,000
Operating Loss Carryforwards [Line Items]
Federal net operating loss	154,000,000					154,000,000
State net operating loss carryforward	950,000,000	[12]				950,000,000	[12]
Deferred taxes	51,000,000					51,000,000
Valuation allowance	1,000,000					1,000,000
Tax Effects Of Temporary Differences [Line Items]
Plant basis differences	(1,553,000,000)					(1,553,000,000)		(1,220,000,000)
Deferred pension and other post-retirement obligation	(12,000,000)					(12,000,000)		(93,000,000)
Deferred debt refinancing costs	(4,000,000)					(4,000,000)		(4,000,000)
Net operating losses	105,000,000					105,000,000
Other, net	(186,000,000)					(186,000,000)		(226,000,000)
Deferred income tax liabilities, net	(1,650,000,000)					(1,650,000,000)		(1,543,000,000)
Unamortized investment tax credits	(6,000,000)					(6,000,000)		(8,000,000)
Total deferred income tax liabilities, net and unamortized investment tax credits	(1,656,000,000)					(1,656,000,000)		(1,551,000,000)
Baltimore Gas and Electric Company [Member] | Federal Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit						(97,000,000)		(71,000,000)	(201,000,000)
Deferred Income Tax Expense Benefit						101,000,000		130,000,000	279,000,000
Investment tax credit amortization						(1,000,000)		(1,000,000)	(1,000,000)
Baltimore Gas and Electric Company [Member] | State Income Tax Expense Benefit Continuing Operations [Member]
Income Tax Expense Benefit Continuing Operations [Line Items]
Current Income Tax Expense Benefit									(2,000,000)
Deferred Income Tax Expense Benefit						$ 4,000,000		$ 17,000,000	$ 22,000,000

[1] Exelon activity for the twelve months ended December 31, 2012 includes the results of Constellation and BGE for March 12, 2012 - December 31, 2012. Generation activity for the twelve months ended December 31, 2012 includes the results of Constellation for March 12, 2012 - December 31, 2012.

[2] Prior to the close of the merger, the Registrants recorded the applicable taxes on merger transaction costs assuming the merger would not be completed. Upon closing of the merger, the Registrants reversed such taxes for those merger transaction costs that were determined to be non tax-deductible upon successful completion of a merger.

[3] Exelon's federal net operating loss will expire beginning in 2033

[4] Exelon’s federal capital loss carryforwards will expire beginning in 2018

[5] Exelon’s federal general business credit carryforwards will expire beginning in 2033

[6] Exelon’s state net operating losses will expire beginning in 2014

[7] Exelon’s state capital loss carryforwards will expire beginning in 2018

[8] Generation’s state net operating losses will expire beginning in 2014

[9] Generation’s state capital loss carryforwards will expire beginning in 2018

[10] PECO’s state net operating losses will expire beginning in 2032

[11] BGE activity represents the activity for the twelve months ended December 31, 2012, 2011 and 2010.

[12] BGE’s state net operating losses will expire beginning in 2026