Exhibit 12a

UniSource Energy Corporation
Computation of Ratio of Earnings to Fixed Charges

	12 Months Ended
	Dec 31,		Dec. 31,		Dec. 31,		Dec. 31,		Dec. 31,			Dec. 31,
	2010		2009		2008		2007		2006			2005
	- Thousands of Dollars -
Fixed Charges:
Interest on Long-Term Debt	$	65,020	$	58,134	$	70,227	$	73,095	$	75,039		$	76,762
Other Interest (1)		1,651		3,468		1,837		5,480		7,922			3,153
Interest on Capital Lease Obligations		52,540		53,682		57,272		64,499		72,586			79,098
Estimated Interest Portion of Rental Expense		240		345		188		258		326			391
Total Fixed Charges	$	119,451	$	115,629	$	129,524	$	143,332	$	155,873		$	159,404
Net Income	$	111,477	$	104,258	$	14,021	$	58,373	$	67,447		$	46,144
Add:
Discontinued Operations — Net of Tax		—		—		—		—		1,796			5,483
Cumulative Effect of Accounting Change — Net of Tax		—		—		—		—		—			626
Net Income from Continuing Operations		111,477		104,258		14,021		58,373		69,243			52,253
Add (Deduct):
(Income) Losses from Equity Investees		5,570		1,834		713		340		(210	)		(2,113	)
Income Taxes		78,266		64,348		16,976		39,079		43,936			37,623
Total Fixed Charges		119,451		115,629		129,524		143,332		155,873			159,404
Total Earnings before Taxes and Fixed Charges	$	314,764	$	286,069	$	161,234	$	241,124	$	268,842		$	247,167
Ratio of Earnings to Fixed Charges		2.635		2.474		1.245		1.682		1.725			1.551

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