Exhibit 12a

UniSource Energy Corporation
Computation of Ratio of Earnings to Fixed Charges

	9 Months Ended		12 Months Ended			12 Months Ended
	September 30,		September 30,			December 31,		December 31,		December 31,		December 31,		December 31,
	2011		2011			2010*		2009*		2008*		2007*		2006*
	- Thousands of Dollars -
Fixed Charges:
Interest on Long-Term Debt	$	54,240	$	72,277		$	65,020	$	58,134	$	70,227	$	73,095	$	75,039
Other Interest (1)		1,928		3,210			1,651		3,468		1,837		5,480		7,922
Interest on Capital Lease Obligations		33,568		46,565			52,540		53,682		57,272		64,499		72,586
Estimated Interest Portion of Rental Expense		118		178			240		345		188		258		326
Total Fixed Charges	$	89,854	$	122,230		$	119,451	$	115,629	$	129,524	$	143,332	$	155,873
Net Income	$	101,787	$	113,039		$	112,984	$	105,901	$	16,955	$	60,712	$	68,524
Add:
Discontinued Operations Loss — Net of Tax		—		—			—		—		—		—		1,796
Net Income from Continuing Operations		101,787		113,039			112,984		105,901		16,955		60,712		70,320
Add (Deduct):
(Income) Losses from Equity Investees		—		(64	)		5,570		1,834		713		340		(210	)
Income Taxes		62,916		67,818			76,921		63,232		18,747		40,274		42,143
Total Fixed Charges		89,854		122,230			119,451		115,629		129,524		143,332		155,873
Total Earnings before Taxes and Fixed Charges	$	254,557	$	303,023		$	314,926	$	286,596	$	165,939	$	244,658	$	268,126
Ratio of Earnings to Fixed Charges		2.833		2.479			2.636		2.479		1.281		1.707		1.720

*	As revised. See Note 1 to the financial statements for more information.
(1)	Excludes recognition of Allowance for Borrowed Funds Used During Construction.