Commonwealth Edison 8-K Entry into a Material Definitive Agreement

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.