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Utility Capital Assets (Tables)
 12 Months Ended
Dec. 31, 2016
Regulated Operations [Abstract]  
Schedule of Public Utility Property, Plant, and Equipment
The service life ranges and weighted average remaining service life of the Corporation’s distribution, transmission, generation and other assets as at December 31 were as follows.

 
 
2016
2015
(Years)
Service Life Ranges
Weighted Average Remaining Service Life
 
Service Life Ranges
Weighted Average Remaining Service Life
Distribution
 
 
 
 
 
 
Electric
5-80
32
 
5-80
30
 
Gas
7-95
33
 
4-95
33
Transmission
 
 
 
 
 
 
Electric
20-80
41
 
20-80
29
 
Gas
7-80
34
 
7-80
36
Generation
5-85
26
 
5-85
27
Other
3-70
14
 
3-70
8
 
 
2016
(in millions)
Cost
 
Accumulated Depreciation
 
Net Book Value
Distribution
 
 
 
 
 
 
Electric
$
9,616

 
$
(2,752
)
 
$
6,864

 
Gas
3,956

 
(1,096
)
 
2,860

Transmission


 


 


 
Electric
12,616

 
(2,876
)
 
9,740

 
Gas
1,776

 
(562
)
 
1,214

Generation
6,884

 
(2,474
)
 
4,410

Other
3,497

 
(1,096
)
 
2,401

Assets under construction
1,559

 
—

 
1,559

Land
289

 
—

 
289

 
 
$
40,193

 
$
(10,856
)
 
$
29,337

10. UTILITY CAPITAL ASSETS (cont’d)

 
 
2015
(in millions)
Cost
 
Accumulated Depreciation
 
Net Book Value
Distribution
 
 
 
 
 
 
Electric
$
9,245

 
$
(2,634
)
 
$
6,611

 
Gas
3,829

 
(1,021
)
 
2,808

Transmission


 


 


 
Electric
3,093

 
(997
)
 
2,096

 
Gas
1,735

 
(531
)
 
1,204

Generation
6,465

 
(2,241
)
 
4,224

Other
2,429

 
(849
)
 
1,580

Assets under construction
886

 
—

 
886

Land
186

 
—

 
186

 
 
$
27,868

 
$
(8,273
)
 
$
19,595
Schedule of Jointly Owned Facilities
As at December 31, 2016, interests in jointly owned facilities consisted of the following.
 
Ownership
 
Accumulated
Net Book
(in millions)
%
Cost
Depreciation
Value
San Juan Units 1 and 2
50.0
$
670

$
(352
)
$
318

Navajo Units 1, 2 and 3
7.5
206

(153
)
53

Four Corners Units 4 and 5
7.0
185

(103
)
82

Luna Energy Facility
33.3
73

(3
)
70

Gila River Common Facilities
25.0
44

(15
)
29

Springerville Coal Handling Facilities (1)
83.0
270

(108
)
162

Transmission Facilities
1.0-80.0
750

(236
)
514

 
 
$
2,198

$
(970
)
$
1,228

(1) 
In 2016 UNS Energy reclassified an additional 17.05% undivided interest in the Springerville Coal Handling Facilities from assets held for sale (Note 6).