Exhibit 12.1

Commonwealth Edison Company

Ratio of Earnings to Fixed Charges

	Twelve Months Ended December 31,														Nine Months Ended September 30,
	2008		2009			2010			2011			2012			2013
Pre-tax income from continuing operations	$	329	$	602		$	693		$	666		$	618		$	233
Plus: Loss from equity investees		9		—			—			—			—			—
Less: Capitalized interest		3		(3	)		(2	)		(4	)		(3	)		(3	)
Pre-tax income from continuing operations after adjustment for loss from equity investees and capitalized interest	$	341	$	599		$	691		$	662		$	615		$	230
Fixed Charges:
Interest expensed and capitalized, amortization of debt discount and premium on all indebtedness(a)	$	323	$	301		$	368		$	330		$	297		$	499
Interest component of rental expense(b)		8		7			6			6			6			4
Total fixed charges		331		308			374			336			303			503
Pre-tax income from continuing operations after adjustment for loss from equity investees and capitalized interest plus fixed charges	$	672	$	907		$	1,065		$	998		$	918		$	733
Ratio of earnings to fixed charges		2.0		2.9			2.8			3.0			3.0			1.5

a) Includes interest expense of $291 million for the nine months ended September 30, 2013, related to the remeasurement of the like-kind exchange tax position. See Note 12—Income Taxes of the Exelon Form 10-Q for the quarter ended September 30, 2013, for additional information regarding the like-kind exchange tax position.

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