8.	Fair Value of Financial Assets and Liabilities

Fair Value Measurements

The accounting guidance for fair value measurements and disclosures provides a single definition of fair value and requires certain disclosures about assets and liabilities measured at fair value. A hierarchal framework for disclosing the observability of the inputs utilized in measuring assets and liabilities at fair value is established by this guidance. The three levels in the hierarchy are as follows:

Level 1 - Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. The types of assets and liabilities included in Level 1 are highly liquid and actively traded instruments with quoted prices.

Level 2 - Pricing inputs are other than quoted prices in active markets, but are either directly or indirectly observable as of the reporting date. The types of assets and liabilities included in Level 2 are typically either comparable to actively traded securities or contracts, or priced with discounted cash flow or option pricing models using highly observable inputs.

Level 3 - Significant inputs to pricing have little or no observability as of the reporting date. The types of assets and liabilities included in Level 3 are those valued with models requiring significant management judgment or estimation.

Specific valuation methods include the following:

Interest rate derivatives - The fair value of interest rate derivatives are based on broker quotes utilizing market interest rate curves.

Commodity derivatives - The methods utilized to measure the fair value of commodity derivatives include the use of forward prices and volatilities to value commodity forwards and options. Levels are assigned to these fair value measurements based on the significance of the use of subjective forward price and volatility forecasts for commodities and delivery locations with limited observability, or the significance of contractual settlements that extend to periods beyond those readily observable on active exchanges or quoted by brokers.

PSCo continuously monitors the creditworthiness of the counterparties to its commodity derivative contracts and assesses each counterparty's ability to perform on the transactions set forth in the contracts. Given this assessment, as well as an assessment of the impact of PSCo's own credit risk when determining the fair value of commodity derivative liabilities, the impact of considering credit risk was immaterial to the fair value of commodity derivative assets and liabilities presented in the consolidated balance sheets.

Derivative Instruments Fair Value Measurements

PSCo enters into derivative instruments, including forward contracts, futures, swaps and options, for trading purposes and to reduce risk in connection with changes in interest rates, utility commodity prices and vehicle fuel prices.

Interest Rate Derivatives - PSCo enters into various instruments that effectively fix the interest payments on certain floating rate debt obligations or effectively fix the yield or price on a specified benchmark interest rate for an anticipated debt issuance for a specific period. These derivative instruments are generally designated as cash flow hedges for accounting purposes.

At Sept. 30, 2011, accumulated OCI related to interest rate derivatives included $1.5 million of net gains expected to be reclassified into earnings during the next 12 months as the related hedged interest rate transactions impact earnings.

At Sept. 30, 2011, PSCo had unsettled interest rate swaps outstanding with a total notional amount of $225 million. These interest rate swaps were designated as hedges, and as such, changes in fair value are recorded to OCI.

Short-Term Wholesale and Commodity Trading Risk - PSCo conducts various short-term wholesale and commodity trading activities, including the purchase and sale of electric capacity, energy and energy-related products. PSCo's risk management policy allows management to conduct these activities within guidelines and limitations as approved by its risk management committee, which is made up of management personnel not directly involved in the activities governed by this policy.

Commodity Derivatives - PSCo enters into derivative instruments to manage variability of future cash flows from changes in commodity prices in its electric and natural gas operations, as well as for trading purposes. This could include the purchase or sale of energy or energy-related products, natural gas to generate electric energy, gas for resale, and vehicle fuel.

At Sept. 30, 2011, PSCo had vehicle fuel contracts designated as cash flow hedges extending through December 2014. PSCo also enters into derivative instruments that mitigate commodity price risk on behalf of electric and natural gas customers but are not designated as qualifying hedging transactions. Changes in the fair value of non-trading commodity derivative instruments are recorded in OCI or deferred as a regulatory asset or liability. The classification as a regulatory asset or liability is based on commission approved regulatory recovery mechanisms. PSCo recorded immaterial amounts to income related to the ineffectiveness of cash flow hedges for the three and nine months ended Sept. 30, 2011 and 2010.

At Sept. 30, 2011, accumulated OCI related to commodity derivative cash flow hedges included $0.1 million of net gains expected to be reclassified into earnings during the next 12 months as the hedged transactions occur.

Additionally, PSCo enters into commodity derivative instruments for trading purposes not directly related to commodity price risks associated with serving its electric and natural gas customers. Changes in the fair value of these commodity derivatives are recorded in electric operating revenues, net of amounts credited to customers under margin-sharing mechanisms.

The following table details the gross notional amounts of commodity forwards and options at Sept. 30, 2011 and Dec. 31, 2010:

(Amounts in Thousands) (a) (b)	Sept. 30, 2011		Dec. 31, 2010
Megawatt hours (MWh) of electricity		1,834		2,418
MMBtu of natural gas		55,103		59,465
Gallons of vehicle fuel		293		360

(a)	Amounts are not reflective of net positions in the underlying commodities.

(b)	Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

Financial Impact of Qualifying Cash Flow Hedges - The impact of qualifying interest rate and vehicle fuel cash flow hedges on PSCo's accumulated OCI, included as a component of common stockholder's equity, is detailed in the following tables:

	Three Months Ended Sept. 30,
(Thousands of Dollars)	2011			2010
Accumulated other comprehensive income related to cash flow hedges at July 1	$	6,793		$	7,704
After-tax net unrealized (losses) gains related to derivatives accounted for as hedges		(14,428	)		13
After-tax net realized gains on derivative transactions reclassified into earnings		(381	)		(126	)
Accumulated other comprehensive (loss) income related to cash flow hedges at Sept. 30	$	(8,016	)	$	7,591

	Nine Months Ended Sept. 30,
(Thousands of Dollars)	2011			2010
Accumulated other comprehensive income related to cash flow hedges at Jan. 1	$	7,457		$	8,101
After-tax net unrealized losses related to derivatives accounted for as hedges		(14,346	)		(95	)
After-tax net realized gains on derivative transactions reclassified into earnings		(1,127	)		(415	)
Accumulated other comprehensive (loss) income related to cash flow hedges at Sept. 30	$	(8,016	)	$	7,591

PSCo had no derivative instruments designated as fair value hedges during the three and nine months ended Sept. 30, 2011 and 2010. Therefore, no gains or losses from fair value hedges or related hedged transactions were recognized for these periods.

The following tables detail the impact of derivative activity during the three and nine months ended Sept. 30, 2011 and 2010, respectively, on OCI, regulatory assets and liabilities, and income:

	Three Months Ended Sept. 30, 2011
	Fair Value Changes Recognized						Pre-Tax Amounts Reclassified into
	During the Period in:						Income During the Period from:						Pre-Tax Losses
	Other			Regulatory			Other			Regulatory			Recognized
	Comprehensive			Assets and			Comprehensive			Assets and			During the Period
(Thousands of Dollars)	Loss			Liabilities			Loss			Liabilities			in Income
Derivatives designated as cash flow hedges
Interest rate	$	(23,178	)	$	-		$	(589	) (a)	$	-		$	-
Vehicle fuel and other commodity		(89	)		-			(25	) (c)		-			-
Total	$	(23,267	)	$	-		$	(614	)	$	-		$	-

Other derivative instruments
Trading commodity	$	-		$	-		$	-		$	-		$	(12	) (b)
Natural gas commodity		-			(31,802	)		-			308	(d)		(126	) (b)
Total	$	-		$	(31,802	)	$	-		$	308		$	(138	)

	Nine Months Ended Sept. 30, 2011
	Fair Value Changes Recognized						Pre-Tax Amounts Reclassified into
	During the Period in:						Income During the Period from:						Pre-Tax Gains (Losses)
	Other			Regulatory			Other			Regulatory			Recognized
	Comprehensive			Assets and			Comprehensive			Assets and			During the Period
(Thousands of Dollars)	Income (Loss)			Liabilities			Loss			Liabilities			in Income
Derivatives designated as cash flow hedges
Interest rate	$	(23,178	)	$	-		$	(1,748	) (a)	$	-		$	-
Vehicle fuel and other commodity		44			-			(70	) (c)		-			-
Total	$	(23,134	)	$	-		$	(1,818	)	$	-		$	-

Other derivative instruments
Trading commodity	$	-		$	-		$	-		$	-		$	83	(b)
Natural gas commodity		-			(44,948	)		-			45,527	(d)		(126	) (b)
Total	$	-		$	(44,948	)	$	-		$	45,527		$	(43	)

	Three Months Ended Sept. 30, 2010
	Fair Value Changes Recognized					Pre-Tax Amounts Reclassified into
	During the Period in:					Income During the Period from:						Pre-Tax Losses
	Other		Regulatory			Other			Regulatory			Recognized
	Comprehensive		Assets and			Comprehensive			Assets and			During the Period
(Thousands of Dollars)	Income		Liabilities			Income (Loss)			Liabilities			in Income
Derivatives designated as cash flow hedges
Interest rate	$	-	$	-		$	(589	) (a)	$	-		$	-
Vehicle fuel and other commodity		20		-			386	(c)		-			-
Total	$	20	$	-		$	(203	)	$	-		$	-

Other derivative instruments
Trading commodity	$	-	$	-		$	-		$	-		$	(568	) (b)
Natural gas commodity		-		(51,538	)		-			925	(d)		-
Total	$	-	$	(51,538	)	$	-		$	925		$	(568	)

	Nine Months Ended Sept. 30, 2010
	Fair Value Changes Recognized						Pre-Tax Amounts Reclassified into
	During the Period in:						Income During the Period from:						Pre-Tax Gains (Losses)
	Other			Regulatory			Other			Regulatory			Recognized
	Comprehensive			Assets and			Comprehensive			Assets and			During the Period
(Thousands of Dollars)	Loss			Liabilities			Income (Loss)			Liabilities			in Income
Derivatives designated as cash flow hedges
Interest rate	$	-		$	-		$	(1,747	) (a)	$	-		$	-
Vehicle fuel and other commodity		(154	)		-			1,078	(c)		-			-
Total	$	(154	)	$	-		$	(669	)	$	-		$	-

Other derivative instruments
Trading commodity	$	-		$	-		$	-		$	-		$	(1,090	) (b)
Natural gas commodity		-			(82,824	)		-			5,314	(d)		-
Other		-			-			-			-			134	(b)
Total	$	-		$	(82,824	)	$	-		$	5,314		$	(956	)

(a)	Recorded to interest charges.

(b)	Recorded to electric operating revenues. Portions of these total gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue, as appropriate.

(c)	Recorded to O&M expenses.

(d)	Recorded to cost of natural gas sold and transported; these derivative settlement gains and losses are shared with natural gas customers through purchased natural gas cost-recovery mechanisms, and reclassified out of income as regulatory assets and liabilities, as appropriate.

Credit Related Contingent Features- Contract provisions of the derivative instruments that PSCo enters into may require the posting of collateral or settlement of the contracts for various reasons, including if PSCo is unable to maintain its credit ratings. If the credit ratings of PSCo were downgraded below investment grade, contracts underlying $6.9 million and $5.6 million of derivative instruments in a liability position at Sept. 30, 2011 and Dec. 31, 2010, respectively, would have required PSCo to post collateral or settle applicable contracts, which would have resulted in payments to counterparties of $6.9 million and $9.8 million, respectively. At Sept. 30, 2011 and Dec. 31, 2010, there was no collateral posted on these specific contracts.

PSCo's derivative instruments are also subject to contract provisions that contain adequate assurance clauses. These provisions allow counterparties to seek performance assurance, including cash collateral, in the event that a given utility subsidiary's ability to fulfill its contractual obligations is reasonably expected to be impaired. PSCo had no collateral posted related to adequate assurance clauses in derivative contracts as of Sept. 30, 2011 and Dec. 31, 2010.

Recurring Fair Value Measurements- The following table presents for each of the hierarchy levels, PSCo's assets and liabilities that are measured at fair value on a recurring basis at Sept. 30, 2011:

	Sept. 30, 2011
	Fair Value
							Fair Value		Counterparty
(Thousands of Dollars)	Level 1		Level 2		Level 3		Total		Netting (b)			Total
Current derivative assets
Derivatives designated as cash flow hedges:
Vehicle fuel and other commodity	$	-	$	65	$	-	$	65	$	(65	)	$	-
Other derivative instruments:
Trading commodity		74		7,176		-		7,250		(3,818	)		3,432
Total current derivative assets	$	74	$	7,241	$	-	$	7,315	$	(3,883	)		3,432
Purchased power agreements (a)													2,346
Current derivative instruments												$	5,778
Noncurrent derivative assets
Derivatives designated as cash flow hedges:
Vehicle fuel and other commodity	$	-	$	34	$	-	$	34	$	-		$	34
Other derivative instruments:
Trading commodity		-		7,652		-		7,652		(2,821	)		4,831
Total noncurrent derivative assets	$	-	$	7,686	$	-	$	7,686	$	(2,821	)		4,865
Purchased power agreements (a)													10,751
Noncurrent derivative instruments												$	15,616

Current derivative liabilities
Derivatives designated as cash flow hedges:
Interest rate	$	-	$	23,178	$	-	$	23,178	$	-		$	23,178
Other derivative instruments:
Trading commodity		120		6,716		-		6,836		(3,852	)		2,984
Natural gas commodity		-		39,144		-		39,144		(2,064	)		37,080
Total current derivative liabilities	$	120	$	69,038	$	-	$	69,158	$	(5,916	)		63,242
Purchased power agreements (a)													5,621
Current derivative instruments												$	68,863
Noncurrent derivative liabilities
Other derivative instruments:
Trading commodity	$	-	$	6,707	$	-	$	6,707	$	(2,821	)	$	3,886
Total noncurrent derivative liabilities	$	-	$	6,707	$	-	$	6,707	$	(2,821	)		3,886
Purchased power agreements (a)													35,486
Noncurrent derivative instruments												$	39,372

(a)

In 2003, as a result of implementing new guidance on the normal purchase exception for derivative accounting, PSCo began recording several long-term purchased power agreements at fair value due to accounting requirements related to underlying price adjustments. As these purchases are recovered through normal regulatory recovery mechanisms in the respective jurisdictions, the changes in fair value for these contracts were offset by regulatory assets and liabilities. During 2006, PSCo qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.

(b)

The accounting guidance for derivatives and hedging permits the netting of receivables and payables for derivatives and related collateral amounts when a legally enforceable master netting agreement exists between PSCo and a counterparty. A master netting agreement is an agreement between two parties who have multiple contracts with each other that provides for the net settlement of all contracts in the event of default on or termination of any one contract.

PSCo recognizes transfers between levels as of the beginning of each period. There were no transfers of amounts between levels for the three and nine months ended Sept. 30, 2011. The following table presents the transfers that occurred between levels during the three and nine months ended Sept. 30, 2010:

	From Level 3 to Level 2 (a) (b)
	Three Months Ended			Nine Months Ended
(Thousands of Dollars)	Sept. 30, 2010			Sept. 30, 2010
Trading commodity derivatives not designated as cash flow hedges:
Current assets	$	148		$	1,888
Noncurrent assets		-			4,988
Current liabilities		-			(1,265	)
Noncurrent liabilities		(833	)		(3,724	)
Total	$	(685	)	$	1,887

(a)	The transfer of amounts from Level 3 to Level 2 is due to the valuation of certain long-term derivative contracts for which observable commodity pricing forecasts became a more significant input during the period.

(b)	There were no transfers of amounts from Level 2 to Level 3.

The following table presents for each of the hierarchy levels, PSCo's assets and liabilities that are measured at fair value on a recurring basis at Dec. 31, 2010:

	Dec. 31, 2010
	Fair Value
							Fair Value		Counterparty
(Thousands of Dollars)	Level 1		Level 2		Level 3		Total		Netting (b)			Total
Current derivative assets
Derivatives designated as cash flow hedges:
Vehicle fuel and other commodity	$	-	$	56	$	-	$	56	$	-		$	56
Other derivative instruments:
Trading commodity		-		5,765		-		5,765		(2,633	)		3,132
Natural gas commodity		-		1,396		-		1,396		(1,019	)		377
Total current derivative assets	$	-	$	7,217	$	-	$	7,217	$	(3,652	)		3,565
Purchased power agreements (a)													2,729
Current derivative instruments												$	6,294
Noncurrent derivative assets
Derivatives designated as cash flow hedges:
Vehicle fuel and other commodity	$	-	$	68	$	-	$	68	$	-		$	68
Other derivative instruments:
Trading commodity		-		6,770		-		6,770		(2,118	)		4,652
Natural gas commodity		-		1,111		-		1,111		(211	)		900
Total noncurrent derivative assets	$	-	$	7,949	$	-	$	7,949	$	(2,329	)		5,620
Purchased power agreements (a)													12,415
Noncurrent derivative instruments												$	18,035

	Dec. 31, 2010
	Fair Value
							Fair Value		Counterparty
(Thousands of Dollars)	Level 1		Level 2		Level 3		Total		Netting (b)			Total
Current derivative liabilities
Other derivative instruments:
Trading commodity	$	-	$	5,192	$	-	$	5,192	$	(2,669	)	$	2,523
Natural gas commodity		-		41,753		-		41,753		(20,969	)		20,784
Total current derivative liabilities	$	-	$	46,945	$	-	$	46,945	$	(23,638	)		23,307
Purchased power agreements (a)													5,740
Current derivative instruments												$	29,047
Noncurrent derivative liabilities
Other derivative instruments:
Trading commodity	$	-	$	5,526	$	-	$	5,526	$	(2,118	)	$	3,408
Natural gas commodity		-		350		-		350		(211	)		139
Total noncurrent derivative liabilities	$	-	$	5,876	$	-	$	5,876	$	(2,329	)		3,547
Purchased power agreements (a)													39,673
Noncurrent derivative instruments												$	43,220

(a)

(b)

There were no changes in Level 3 recurring fair value measurements for the three and nine months ended Sept. 30, 2011. The following table presents the changes in Level 3 recurring fair value measurements for the three and nine months ended Sept. 30, 2010:

(Thousands of Dollars)	Three Months Ended Sept. 30, 2010			Nine Months Ended Sept. 30, 2010
Balance at beginning of period	$	599		$	804
Purchases		-			(134	)
Settlements		(308	)		(436	)
Transfers out of Level 3		685			(1,887	)
(Losses) gains recognized in earnings (a)		(976	)		1,653
Balance at Sept. 30	$	-		$	-

(a)	These amounts relate to commodity derivatives held at the end of the period.

Fair Value of Long-Term Debt

The historical cost and fair value of PSCo's long-term debt are as follows:

	Sept. 30, 2011				Dec. 31, 2010
	Historical				Historical
(Thousands of Dollars)	Cost		Fair Value		Cost		Fair Value
Long-term debt, including current portion	$	3,482,594	$	4,011,404	$	3,235,223	$	3,531,729

The fair value of PSCo's long-term debt is estimated based on the quoted market prices for the same or similar issues, or the current rates for debt of the same remaining maturities and credit quality. The fair value estimates presented are based on information available to management as of Sept. 30, 2011 and Dec. 31, 2010. These fair value estimates have not been comprehensively revalued for purposes of these consolidated financial statements since that date and current estimates of fair values may differ significantly.

As of Sept. 30, 2011 and Dec. 31, 2010, the historical cost of cash and cash equivalents, accounts receivable, accounts payable and short-term debt are representative of fair value because of the short-term nature of these instruments.