Commonwealth Edison 8-K Entry into a Material Definitive Agreement

Exhibit 12.1

Commonwealth Edison Company

Ratio of Earnings to Fixed Charges

	12 Months Ended December 31,															9 Months Ended September 30,
	2009			2010			2011			2012			2013			2014
Pre-tax income from continuing operations	$	602		$	693		$	666		$	618		$	401		$	556
Plus: (Income) or Loss from equity investees		—			—			—			—			—			—
Less: Capitalized interest		(3	)		(2	)		(4	)		(3	)		(5	)		(2	)
Pre-tax income from continuing operations after adjustment for income or loss from equity investees and capitalized interest	$	599		$	691		$	662		$	615		$	396		$	554
Fixed Charges:
Interest expensed and capitalized, amortization of debt discount and premium on all indebtedness (a)	$	301		$	368		$	330		$	297		$	593		$	237
Interest component of rental expense (b)		7			6			6			6			5			4
Total fixed charges		308			374			336			303			598			241
Pre-tax income from continuing operations after adjustment for income or loss from equity investees, capitalized interest and preference security dividend requirements plus fixed charges	$	907		$	1,065		$	998		$	918		$	994		$	795
Ratio of earnings to combined fixed charges and preferred stock dividends		2.9			2.8			3.0			3.0			1.7			3.3

(a) Includes interest expense of $5 million for the nine months ended September 30, 2014, 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, 2014, 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.