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Summary of significant accounting policies: (Tables)
 12 Months Ended
Dec. 31, 2018
Summary of significant accounting policies:  
Schedule of sales to members

 

 

 

 

 

 

 

 

 

 

 

(dollars in thousands)

 

    

2018

    

2017

 

2016

Capacity revenues

 

$

927,419

 

$

912,421

$

949,193

Energy revenues

 

 

551,960

 

 

521,409

 

557,614

Total

 

$

1,479,379

 

$

1,433,830

$

1,506,807

 

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

 

 

 

 

 

 

 

 

 

 

 

    

2018

    

2017

 

2016

Jackson EMC

 

14.1

%  

 

14.7

%  

 

14.3

%

Cobb EMC

 

13.9

%  

 

14.3

%  

 

13.7

%

Sawnee EMC

 

n/a

 

 

n/a

 

 

10.5

%

 

Schedule reflecting details of asset retirement obligations included in the consolidated balance sheets

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(dollars in thousands)

 

    

Nuclear

    

Coal Ash

    

Other

    

Total

Balance at December 31, 2017

 

$

548,574

 

$

161,755

 

$

24,668

 

$

734,997

Liabilities settled

 

 

(1,686)

 

 

(1,596)

 

 

(1,398)

 

 

(4,680)

Accretion

 

 

32,857

 

 

4,238

 

 

995

 

 

38,090

Change in cash flow estimates

 

 

79,211

 

 

161,851

 

 

8,094

 

 

249,156

Balance at December 31, 2018

 

$

658,956

 

$

326,248

 

$

32,359

 

$

1,017,563

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(dollars in thousands)

 

    

Nuclear

    

Coal Ash

    

Other

    

Total

Balance at December 31, 2016

 

$

517,565

 

$

156,465

 

$

24,021

 

$

698,051

Liabilities settled

 

 

(17)

 

 

(943)

 

 

(1,185)

 

 

(2,145)

Accretion

 

 

31,026

 

 

4,629

 

 

1,019

 

 

36,674

Change in cash flow estimates

 

 

 —

 

 

1,604

 

 

813

 

 

2,417

Balance at December 31, 2017

 

$

548,574

 

$

161,755

 

$

24,668

 

$

734,997

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(dollars in thousands)

 

    

Hatch Unit

    

Hatch Unit

    

Vogtle Unit

    

Vogtle Unit

2018 site study

 

No. 1

 

No. 2

 

No. 1

 

No. 2

Expected start date of decommissioning

 

2034

 

2038

 

2047

 

2049

Estimated costs based on site study in 2018 dollars:

 

 

 

 

 

 

 

 

 

 

 

 

Radiated structures

 

$

209,000

 

$

231,000

 

$

188,000

 

$

206,000

Spent fuel management

 

 

54,000

 

 

49,000

 

 

55,000

 

 

51,000

Non-radiated structures

 

 

14,000

 

 

19,000

 

 

23,000

 

 

29,000

Total estimated site study costs

 

$

277,000

 

$

299,000

 

$

266,000

 

$

286,000

 

Schedule of external and internal trust funds by type of investment

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2018

External Trust Funds:

 

 

 

 

 

 

 

 

 

 

 

 

Cost

 

 

 

Net

 

Unrealized

 

Fair Value

 

    

12/31/2017

    

Purchases

    

Proceeds(1)

    

Gain(Loss)

    

12/31/2018

Equity

 

$

203,622

 

$

12,186

 

$

(7,789)

 

$

49,475

 

$

257,494

Debt

 

 

164,901

 

 

445,353

 

 

(443,712)

 

 

(2,108)

 

 

164,434

Other

 

 

141

 

 

370

 

 

(1,621)

 

 

 —

 

 

(1,110)

 

 

$

368,664

 

$

457,909

 

$

(453,122)

 

$

47,367

 

$

420,818

 

(1)

Also included in net proceeds are net realized gains or losses, interest income, dividends, contributions and fees of $4,786,000.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2018

Internal Funds:

    

 

    

 

    

 

    

 

    

 

 

 

Cost

 

 

 

Net

 

Unrealized

 

Fair Value

 

    

12/31/2017

    

Purchases

    

Proceeds(1)

    

Gain(Loss)

    

12/31/2018

Equity

 

$

43,698

 

$

 —

 

$

596

 

$

6,373

 

$

50,667

Debt

 

 

33,540

 

 

161,454

 

 

(156,611)

 

 

(246)

 

 

38,137

 

 

$

77,238

 

$

161,454

 

$

(156,015)

 

$

6,127

 

$

88,804

 

(1)

Also included in net proceeds are net realized gains or losses, interest income, dividends, contributions and fees of $689,000.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2017

External Trust Funds:

 

 

 

 

 

 

 

 

 

 

 

 

Cost

 

 

 

Net

 

Unrealized

 

Fair Value

 

    

12/31/2016

    

Purchases

    

Proceeds(1)

    

Gain(Loss)

    

12/31/2017

Equity

 

$

200,595

 

$

61,406

 

$

(44,607)

 

$

76,221

 

$

293,615

Debt

 

 

148,011

 

 

388,609

 

 

(384,199)

 

 

170

 

 

152,591

Other

 

 

351

 

 

98

 

 

(1,600)

 

 

 —

 

 

(1,151)

 

 

$

348,957

 

$

450,113

 

$

(430,406)

 

$

76,391

 

$

445,055

 

(1)

Also included in net proceeds are net realized gains or losses, interest income, dividends, contributions and fees of $19,707,000.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2017

Internal Funds:

    

 

    

 

    

 

    

 

    

 

 

 

Cost

 

 

 

Net

 

Unrealized

 

Fair Value

 

    

12/31/2016

    

Purchases

    

Proceeds(1)

    

Gain(Loss)

    

12/31/2017

Equity

 

$

38,798

 

$

 —

 

$

4,900

 

$

11,669

 

$

55,367

Debt

 

 

26,207

 

 

73,153

 

 

(65,820)

 

 

 —

 

 

33,540

 

 

$

65,005

 

$

73,153

 

$

(60,920)

 

$

11,669

 

$

88,907

 

(1)

Also included in net proceeds are net realized gains or losses, interest income, dividends, contributions and fees of $12,232,800.
Schedule of annual depreciation rates

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Range of

 

 

 

 

 

 

 

 

 

 

 

Useful Life in

 

 

 

 

 

 

 

 

 

 

    

years*

    

2018

    

    

2017

    

 

2016

 

Steam production

 

49-65

 

2.57

%  

 

2.91

%  

 
2.84

%

Nuclear production

 

37-60

 

1.92

%  

 

1.96

%  

 
1.96

%

Hydro production

 

50

 

2.00

%  

 
2.00

%  

 
2.00

%

Other production

 

30-35

 

2.61

%  

 

2.58

%  

 
2.55

%

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 2018.

Schedule of regulatory assets and liabilities

 

 

 

 

 

 

 

 

 

2018

 

2017

 

    

(dollars in thousands)

Regulatory Assets:

 

 

 

 

 

 

Premium and loss on reacquired debt(a)

 

$

46,315

 

$

52,989

Amortization on capital leases(b)

 

 

34,918

 

 

33,846

Outage costs(c)

 

 

36,352

 

 

40,525

Asset retirement obligations – Ashpond and other(k)

 

 

137,835

 

 

68,289

Asset retirement obligations – Nuclear(k)

 

 

7,031

 

 

 0

Depreciation expense(d)

 

 

41,244

 

 

42,667

Deferred charges related to Vogtle Units No. 3 and No. 4 training costs(e)

 

 

51,549

 

 

48,702

Interest rate options cost(f)

 

 

116,960

 

 

112,102

Deferral of effects on net margin – Smith Energy Facility(g)

 

 

160,509

 

 

166,454

Other regulatory assets(m)

 

 

22,350

 

 

19,510

Total Regulatory Assets

 

$

655,063

 

$

585,084

 

 

 

 

 

 

 

Regulatory Liabilities:

 

 

 

 

 

 

Accumulated retirement costs for other obligations(h)

 

$

13,873

 

$

12,813

Deferral of effects on net margin – Hawk Road Energy Facility(g)

 

 

19,101

 

 

19,553

Major maintenance reserve(i)

 

 

45,547

 

 

47,087

Amortization on capital leases(b)

 

 

17,156

 

 

20,055

Deferred debt service adder(j)

 

 

105,192

 

 

95,695

Asset retirement obligations – Nuclear(k)

 

 

 0

 

 

53,571

Revenue deferral plan(l)

 

 

15,670

 

 

 0

Other regulatory liabilities(m)

 

 

2,459

 

 

2,875

Total Regulatory Liabilities

 

$

218,998

 

$

251,649

Net regulatory assets

 

$

436,065

 

$

333,435

 

(a)

Represents premiums paid, together with unamortized transaction costs related to reacquired debt that are being amortized over the lives of the refunding debt, which range up to 25 years.

(b)

Represents the difference between expense recognized for rate-making purposes versus financial statement purposes related to capital lease payments and the aggregate of the amortization of the asset and interest on the obligation.

(c)

Consists of both coal‑fired maintenance and nuclear refueling outage costs. Coal-fired outage costs are amortized on a straight‑line basis to expense over periods up to 48 months, depending on the operating cycle of each unit. Nuclear refueling outage costs are amortized on a straight‑line basis to expense over the 18 or 24 -month operating cycles of each unit.

(d)

Prior to Nuclear Regulatory Commission (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.

(e)

Deferred charges consist of training related costs, including interest and carrying costs of such training. Amortization will commence effective with the commercial operation date of each unit and amortized to expense over the life of the units.

(f)

Deferral of premiums paid to purchase interest rate options used to hedge interest rates on certain borrowings, related carrying costs and other incidentals associated with construction of Vogtle Units No. 3 and No. 4. Amortization will commence in February 2020 and continue through February 2044, the life of the DOE-guaranteed loan which is financing a portion of the construction project.

(g)

Effects on net margin for Smith and Hawk Road Energy Facilities were deferred through the end of 2015 and are being amortized over the remaining life of each respective plant.

(h)

Represents the accrual of retirement costs associated with long-lived assets for which there are no legal obligations to retire the assets.

(i)

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

(j)

Represents collections to fund certain debt payments to be made through the end of 2025 which will be in excess of amounts collected through depreciation expense; the deferred credits will be amortized over the remaining useful life of the plants.

(k)

Represents the difference in the timing of recognition of decommissioning costs for financial statement purposes versus ratemaking purposes, as well as the deferral of unrealized gains and losses of funds set aside for decommissioning.

(l)

Deferred revenues under a  rate management program that allows for additional collections over a five-year period beginning in 2018. These amounts will be amortized to income and applied to member billings over the subsequent five-year period.

(m)

The amortization periods for other regulatory assets range up to 31 years and the amortization periods of other regulatory liabilities range up to 8 years.