June 16, 2015

Future Operating and Maintenance Considerations 

for Existing Coal-Fired Power Plants 

Eric Grol

on behalf of 

NETL’s Strategic Energy Analysis & Planning Division
2

The analysis presented and conclusions drawn herein 

represent solely those views of the authors, and do not 

represent the views of the United States Department of 

Energy.

Disclaimer
3

1. EIA’s $17/kW/year (for capital upgrades) close to NETL 

estimate, but these investments tend to be “lumpy” instead 

of a charge applied annually

2. Due to age of existing coal fleet, these major upgrades 

should be happening now if high CF’s are expected

3. New NETL study quantifies the cost associated with cycling 

existing coal units

Key Areas of Discussion
4

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

Average capacity factor (%)

Unit age in years

Average capacity factor by unit age for coal operations, 1998-2013

Examining Historic Coal Unit Capacity Factors

Unit Capacity Factors Drop Off as they Age

Data source and notes: Data from Ventyx's Energy Velocity. Unit age in each year was calculated then averaged

80%

60%

14%

2

0

2

0

By 2030 average age of 

existing coal plants imply 

capacity factors < 50%

2

0

3

0

Fitted unit-level 

capacity factor 

data

2nd Order Polynomial

Y = -0.0205x2 + 0.7152x + 70.104

Avg. age 

existing 

coal 

plants
Availability Curve for Aging Units vs. fitted 

polynomial of the data

40

45

50

55

60

65

70

75

80

85

90

0 10 20 30 40 50

Boiler Availability, %

Boiler Age, Years

Major Maintenance

Projects

Capital

Investment

Availability after a 

Large Capital Investment

Availability for a 

Constant maintenance

Spending rate

(no major capital investment)

Expected failure

of superheater,

economizer, and

other boiler 

tubing (creep,

corrosion, etc.)

Component Average CapEx

(2012 $/kW)

Miscellaneous Tubing 414.0

Attemperator 0.7

Superheater 11.0

Superheater Outlet 

Header 2.3

Burners and Throats 40.3

Reheater 17.7

Primary Economizer 7.3

Lower Furnace 18.0

Total $511.7/kW*

* Value is ±60% based on site-specific considerations

Fitted unit-level 

data

Year $/kW

1 17

2 17

3 17

4 17

5 17

6 17

7 17

8 17

9 17

10 17

11 17

12 17

13 17

14 17

15 17

16 17

17 17

18 17

19 17

20 17

21 17

22 17

23 17

24 17

25 17

26 17

27 17

28 17

29 17

30 17

Σ 510 $/kW
6

0%

10%

20%

30%

40%

50%

60%

70%

80%

Implied U.S. Coal Capacity Factors

AEO’15

NETL Low-derate

NETL High-derate

EIA, AEO’15; Electric Power Sector

NETL Scenario

Units retire after age 70

Capacity factor de-rate is applied after age 30

Low CF de-rate is 0.56 (% points/yr)

High CF de-rate is 0.94 (% points/yr)

Average Capacity Factors by 2040

EIA 75%

NETL Low 55%

NETL High 46%
7

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

201420152016201720182019202020212022202320242025202620272028202920302031203220332034203520362037203820392040

BkWh

NETL Low derate NETL High derate EIA Gen

Future U.S. Coal Generation Scenarios

AEO 2015 reference case generation

EIA AEO’15 Generation

≈106-127

GW

741 - 887 BkWh

≈66-83

GW

≈37-45

GW

NETL Scenario

Units retire after age 70

Capacity factor de-rate is applied after age 30

Low CF de-rate is 0.56 (% points/yr)

High CF de-rate is 0.94 (% points/yr)

Average Capacity Factors by 2040

EIA 75%

NETL Low 55%

NETL High 46%
8

Component

Time Between Replacement/Major 

Repair

(Years)

Replacement/

Major Repair Cost

(1000$/MW)

Annual (Routine) Maintenance and 

Inspection Cost

(1000$/MW/year)

1 Start 6 Starts 12 Starts 1 Start 6 Starts 12 Starts

Coal Pulverizer 6 5 4 1.33 0.92 1.0 1.0

Steam Drum Annual 

maint. only

Annual 

maint. only

Annual 

maint. only

N/A 1.8 2.2 2.2

Boiler Refractory Annual 

maint. only

Annual 

maint. only

Annual 

maint. only

N/A 1.0 1.5 1.5

Superheater/Headers/Tubes 10 9-10 8-10 8-30.6 0.067 0.080 0.080

Reheater Tubes 10 9-10 8-10 10-23.3 0.067 0.080 0.080

Economizer Tubes 9 8-9 7-8 5.0-10.0 0.067 0.080 0.080

Lower Furnace Tubes 8-10 7-9 6-8 0.15-1.05 0.067 0.080 0.080

Windbox Supports 8-10 7-9 6-8 0.33-0.50 0.067 0.080 0.080

Feedwater Heaters 15-20 18 15 0.67-4.33 0.25 0.25 0.25

Boiler Feed Pumps 8-10 7-9 6-8 0.50 0.25 0.30 0.30

Steam Turbine Generator 

(STG)

0.030 0.030 0.030

Minor Overhaul 2-4 2-3 2-3 0.53 N/A N/A N/A

Major Overhaul 5-10 5-8 5-8 10 N/A N/A N/A

Admission Valves 2-4 2-3 2-3 Incl. in minor 

overhaul cost

Incl. in STG 

cost

Incl. in STG 

cost

Incl. in STG 

cost

Turbine Rotor 5-10 5-8 5-8 Incl. in major 

overhaul cost

Incl. in STG 

cost

Incl. in STG 

cost

Incl. in STG 

cost

LP Turbine Blades 5-10 5-8 5-8 Incl. in major 

overhaul cost

Incl. in STG 

cost

Incl. in STG 

cost

Incl. in STG 

cost

Generator 5-10 5-8 5-8 Incl. in major 

overhaul cost

Incl. in STG 

cost

Incl. in STG 

cost

Incl. in STG 

cost
9

Heat Rate Impacts of Off-Design Operation
10

PJM Dispatch Curve (5-22-15)

Average gas price: ~$2.50/MBtu

Gas Nuc Coal Coke

LOil HOil Coal, Existing Subcritical PC

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

Total Marginal Cost $/M

Wh

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 110,000 120,000 130,000 140,000 150,000 160,000

Cumulative Capacity MW

Minimum Load : 57,353.00 MW

5th Percentile Load : 66,560.00 MW

Average Load : 92,979.00 MW

95th Percentile Load : 120,245.00 MW

Maximum Load : 143,086.00 MW
11

PJM Dispatch Curve (5-22-15)

Average gas price: ~$2.50/MBtu

Gas Nuc Coal Coke

LOil HOil Coal, Existing Subcritical PC (Added Cycling Costs)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

Total Marginal Cost $/M

Wh

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 110,000 120,000 130,000 140,000 150,000 160,000

Cumulative Capacity MW

Minimum Load : 57,353.00 MW

5th Percentile Load : 66,560.00 MW

Average Load : 92,979.00 MW

95th Percentile Load : 120,245.00 MW

Maximum Load : 143,086.00 MW

Only $4/MWh increase, but 

huge impact on marginal cost

(and capacity factor!)