Exelon (EXC) S-3ASR Automatic shelf registration

Exhibit 12.2

Exelon Generation Company, LLC

Ratio of Earnings to Fixed Charges

	Years Ended December 31,															Quarter Ended March 31,
	2007			2008			2009			2010			2011			2012
Pre-tax income from continuing operations		3,387			3,388			3,555			3,150			2,827			396
Plus: (Income) or loss from equity investees		(1	)		1			3			—			1			22
Less: Capitalized interest		(30	)		(33	)		(49	)		(38	)		(49	)		(13	)
Pre-tax income from continuing operations after adjustment for income or loss from equity investees and capitalized interest		3,356			3,356			3,509			3,112			2,779			405
Fixed charges:
Interest expensed and capitalized, amortization of debt discount and premium on all indebtedness (a)		196			170			162			191			219			67
Interest component of rental expense (b)		273			272			212			222			220			43
Total fixed charges		469			442			374			413			439			110
Pre-tax income from continuing operations after adjustment for income or loss from equity investees and capitalized interest plus fixed charges		3,825			3,798			3,883			3,525			3,218			515
Ratio of earnings to fixed charges		8.2			8.6			10.4			8.5			7.3			4.7

(a) Includes interest expense for the quarter ended March 31, 2012 of $1 million and $(5) million, $6 million, $9 million, $0 and $24 million for the years ended December 31, 2011, 2010, 2009, 2008 and 2007, respectively, related to uncertain income tax positions.

(b) Represents one-third of rental expense relating to operating leases, which is a reasonable approximation of the interest factor.