Summary of significant accounting policies: (Tables)

12 Months Ended

Dec. 31, 2012

Summary of significant accounting policies:

Schedule of changes in accumulated other comprehensive margin (deficit)

Accumulated Other Comprehensive Margin (Deficit)
		(dollars in thousands)
		Available-for-sale Securities
Balance at December 31, 2009	$	(1,253	)
Unrealized gain		784
Balance at December 31, 2010		(469	)
Unrealized gain		1,087
Balance at December 31, 2011		618
Unrealized gain		285
Balance at December 31, 2012	$	903

Schedule of members whose revenues accounted for 10% or more of total operating revenues

	2012		2011		2010
Cobb EMC	12.8	%	12.5	%	14.5	%
Jackson EMC	11.9	%	10.9	%	11.6	%
Sawnee EMC(1)	n/a		n/a		10.6	%

(1)

In 2012 and 2011, Sawnee accounted for less than 10% of our total operating revenues.

Schedule of estimated costs of decommissioning of co-owned nuclear facilities

		(dollars in thousands)
2012 site study		Hatch Unit No. 1		Hatch Unit No. 2		Vogtle Unit No. 1		Vogtle Unit No. 2
Expected start date of decommissioning		2034		2038		2047		2049
Estimated costs based on site study in 2012 dollars	$	186,000	$	252,000	$	182,000	$	241,000

Schedule reflecting details of Asset Retirement Obligations included in balance sheets

		(dollars in thousands)
		2012			2011
Balance at beginning of year	$	298,758		$	280,496
Liabilities incurred		1,632			423
Liabilities settled		(1,117	)		(410	)
Accretion		19,554			18,249
Change in Cash Flow Estimate		62,535			–
Balance at end of year	$	381,362		$	298,758

Schedule of annual depreciation rates as approved by Rural Utilities Service

	Range of Useful Life in years*	2012	2011	2010
Steam production	49-65	1.85%	1.88%	1.56%
Nuclear production	37-60	1.54%	1.45%	1.50%
Hydro production	50	2.00%	2.00%	2.00%
Other production	27-33	2.74%	2.74%	2.60%
Transmission	36	2.75%	2.75%	2.75%
General	3-50	2.00-33.33%	2.00-33.33%	2.00-33.33%

* Calculated based on the composite depreciation rates in effect for 2012.

Schedule of regulatory assets and (liabilities)

		(dollars in thousands)
		2012		2011
Regulatory Assets:
Premium and loss on reacquired debt	$	86,319	$	98,538	(a)
Amortization on capital leases		28,670		46,627	(b)
Outage costs		30,901		42,866	(c)
Interest rate swap termination fees		17,326		21,316	(d)
Asset retirement obligations		11,382		29,341	(e)
Depreciation expense		49,785		51,209	(f)
Vogtle Units No. 3 and No. 4 training costs		23,030		17,602	(g)
Interest rate options cost		75,716		30,735	(h)
Effects on net margin- Smith Energy Facility		21,394		3,536	(i)
Other regulatory assets		8,379		9,777	(j)
Total Regulatory Assets	$	352,902	$	351,547
Regulatory Liabilities:
Accumulated retirement costs for other obligations	$	28,846	$	32,687	(e)
Net benefit of Rocky Mountain transactions		4,303		47,783	(k)
Effects on net margin- Hawk Road Energy Facility		17,113		15,811	(i)
Major maintenance sinking fund		30,948		28,524	(l)
Debt service adder		47,486		37,586	(m)
Other regulatory liabilities		1,289		1,609	(j)
Total Regulatory Liabilities	$	129,985	$	164,000
Net regulatory assets	$	222,917	$	187,547

(a)

Represents premiums paid, together with unamortized transaction costs related to reacquired debt amortized over the period of the refunding debt, which range up to 30 years.

(b)

See Note 6 under "Capital Leases." Recovered over the remaining life of the leases through 2031.

(c)

Consists of both coal-fired and nuclear refueling outage costs. Coal-fired outage costs are amortized on a straight-line basis to expense over an 18 to 36-month period. Nuclear refueling outage costs are amortized on a straight-line basis to expense over the 18 to 24-month operating cycles of each unit.

(d)

Represents amount paid on settled interest rate swaps arrangements that are being amortized through 2016 and 2019.

(e)

See Note 1i under "Asset retirement obligations" for a discussion of the asset retirement obligation deferral and recovery and retirement costs for other obligations.

(f)

Prior to NRC approval of a 20 year license extension for Plant Vogtle, we deferred the difference between Plant Vogtle depreciation expense based on the then 40-year operating license and depreciation expense assuming an expected 20-year license extension. Amortization commenced upon NRC approval of the license extension in 2009 and is being amortized over the remaining life of the plant.

(g)

Deferred charges related to Vogtle Units No. 3 and No. 4 training and interest related carrying costs of such training. Amortization will commence effective with the commercial operation date of each unit and amortized over the life of the units.

(h)

Deferral of net loss (gain) associated with the change in fair value of the interest rate options to hedge interest rates on a portion of expected borrowings related to Plant Vogtle Units No.3 and No.4 construction. Amortization will commence effective with the expected principal repayment of the DOE-guaranteed loan and amortized over the expected remaining life of DOE-guaranteed loan which will finance the construction project.

(i)

Effects on net margin for Smith and Hawk Road Energy Facilities will be deferred until the end of 2015 and amortized over the remaining life of each plant.

(j)

The amortization period for other regulatory assets range up to 36 years and the amortization period of other regulatory liabilities range up to 8 years.

(k)

Net benefit associated with Rocky Mountain lease transactions is amortized to income over the 30-year lease-back period. For a discussion of Rocky Mountain leases, see Note 4.

(l)

Represents collections for future major maintenance costs; revenues to be recognized as major maintenance costs are incurred.

(m)

Collections to fund debt payments in excess of depreciation expense through the end of 2025; deferred revenues will be amortized over the remaining useful life of the plants.

Schedule of components of other income

		(dollars in thousands)
		2012		2011		2010
Capital credits from associated companies (Note 4)	$	1,919	$	2,095	$	2,096
Net revenue from Georgia Transmission and Georgia System Operations for shared Administrative and General costs		4,280		4,071		3,834
Miscellaneous other		214		38		(564	)
Total	$	6,413	$	6,204	$	5,366