Exhibit 12a

UniSource Energy Corporation
Computation of Ratio of Earnings to Fixed Charges

	3 Months Ended			12 Months Ended		12 Months Ended
	March 31,			March 31,		Dec. 31,		Dec. 31,		Dec. 31,		Dec. 31,			Dec. 31,
	2010			2010		2009		2008		2007		2006			2005
	-Thousands of Dollars-
Fixed Charges:
Interest on Long-Term Debt	$	15,240		$	58,731	$	58,134	$	70,227	$	73,095	$	75,039		$	76,762
Other Interest (1)		886			3,884		3,468		1,837		5,480		7,922			3,153
Interest on Capital Lease Obligations		13,602			50,650		53,682		57,272		64,499		72,586			79,098
Estimated Interest Portion of Rental Expense		63			322		345		188		258		326			391
Total Fixed Charges	$	29,791		$	113,587	$	115,629	$	129,524	$	143,332	$	155,873		$	159,404
Net Income	$	19,972		$	119,311	$	104,258	$	14,021	$	58,373	$	67,447		$	46,144
Add:
Discontinued Operations Loss — Net of Tax		—			—		—		—		—		1,796			5,483
Cumulative Effect of Accounting Change Loss — Net of Tax		—			—		—		—		—		—			626
Net Income from Continuing Operations		19,972			119,311		104,258		14,021		58,373		69,243			52,253
Add (Deduct):
(Income) Losses from Equity Investees		(76	)		1,731		1,834		713		340		(210	)		(2,113	)
Income Taxes		12,435			73,526		64,348		16,976		39,079		43,936			37,623
Total Fixed Charges		29,791			113,587		115,629		129,524		143,332		155,873			159,404
Total Earnings before Taxes and Fixed Charges	$	62,122		$	308,155	$	286,069	$	161,234	$	241,124	$	268,842		$	247,167
Ratio of Earnings to Fixed Charges		2.085			2.713		2.474		1.245		1.682		1.725			1.551

(1) Excludes recognition of Allowance for Borrowed Funds Used During Construction.