Uns Energy (UNS) POSASR Automatic shelf registration (post-effective amendment)

Exhibit 12

Tucson Electric Power Company

Computation of Ratio of Earnings to Fixed Charges

	9 Months Ended September 30, 2011		12 Months Ended September 30, 2011		12 Months Ended
					December 31, 2010*		December 31, 2009*		December 31, 2008*			December 31, 2007*		December 31, 2006*
					- Thousands of Dollars -
Fixed Charges:
Interest on Long-Term Debt	$	36,493	$	48,617	$	42,378	$	36,226	$	47,456		$	50,230	$	51,422
Other Interest (1)		746		1,612		433		1,571		1,367			4,538		6,436
Interest on Capital Lease Obligations		33,568		46,565		52,534		53,670		57,252			64,477		72,556
Estimated Interest Portion of Rental Expense		19		37		72		106		130			160		188
Total Fixed Charges	$	70,826	$	96,831	$	95,417	$	91,573	$	106,205		$	119,405	$	130,602
Net Income	$	83,773	$	93,898	$	108,260	$	90,688	$	7,206		$	55,591	$	67,306
Add (Deduct):
(Income) Losses from Equity Investees		—		—		—		—		(1,381	)		—		(320	)
Income Taxes		52,104		53,593		59,936		54,220		12,729			36,940		42,845
Total Fixed Charges		70,826		96,831		95,417		91,573		106,205			119,405		130,602
Total Earnings before Taxes and Fixed Charges	$	206,703	$	244,322	$	263,613	$	236,481	$	124,759		$	211,936	$	240,433
Ratio of Earnings to Fixed Charges		2.918		2.523		2.763		2.582		1.175			1.775		1.841

* As revised. For more information, see Note 1 to the financial statements included in the company’s quarterly report on Form 10-Q for the quarter ended September 30, 2011.

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