II 

118TH CONGRESS 

2D SESSION S. 4144 

To improve the reliability and adequacy of the bulk-power system by ensuring 

that key uncertainties in generation, transmission, energy storage systems, and loads are considered in resource adequacy modeling and integrated resource planning, and for other purposes. 

IN THE SENATE OF THE UNITED STATES 

APRIL 17, 2024 

Mr. HEINRICH (for himself, Mr. WYDEN, and Mr. PADILLA) introduced the 

following bill; which was read twice and referred to the Committee on Energy and Natural Resources 

A BILL 

To improve the reliability and adequacy of the bulk-power 

system by ensuring that key uncertainties in generation, 

transmission, energy storage systems, and loads are considered in resource adequacy modeling and integrated 

resource planning, and for other purposes. 

1 Be it enacted by the Senate and House of Representa2 tives of the United States of America in Congress assembled, 

3 SECTION 1. SHORT TITLE. 

4 This Act may be cited as the ‘‘Grid Modeling of Dy5 namic Energy Loads and Resources Act of 2024’’ or the 

6 ‘‘Grid MODEL Act of 2024’’. 


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1 SEC. 2. DEFINITIONS. 

2 In this Act: 

3 (1) BULK-POWER SYSTEM.—The term ‘‘bulk4 power system’’ has the meaning given the term in 

5 section 215(a) of the Federal Power Act (16 U.S.C. 

6 824o(a)). 

7 (2) COMMISSION.—The term ‘‘Commission’’ 

8 means the Federal Energy Regulatory Commission. 

9 (3) EFFECTIVE LOAD CARRYING CAPABILITY; 

10 ELCC.— 

11 (A) IN GENERAL.—The term ‘‘effective 

12 load carrying capability’’ or ‘‘ELCC’’ means the 

13 ability of a generating resource to produce elec14 tricity when the grid needs it, measured as the 

15 additional load (or perfect replacement capac16 ity) that the system can supply with a par17 ticular generator of interest with no net change 

18 in reliability. 

19 (B) CLARIFICATION.—The additional load 

20 (or perfect replacement capacity) referred to in 

21 subparagraph (A)— 

22 (i) may be measured using LOLE, 

23 EUE, or other metrics; and 

24 (ii) may be divided by the nameplate 

25 capacity of the generating resource to yield 

26 a percentage. 


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1 (4) ELECTRIC RELIABILITY ORGANIZATION.— 

2 The term ‘‘Electric Reliability Organization’’ has the 

3 meaning given the term in section 215(a) of the 

4 Federal Power Act (16 U.S.C. 824o(a)). 

5 (5) ELECTRIC UTILITY.—The term ‘‘electric 

6 utility’’ has the meaning given the term in section 

7 3 of the Federal Power Act (16 U.S.C. 796). 

8 (6) EXPECTED UNSERVED ENERGY; EUE.—The 

9 term ‘‘expected unserved energy’’ or ‘‘EUE’’ means 

10 the cumulative amount of energy (in megawatt11 hours) per year that is not provided to customers 

12 due to outages. 

13 (7) INDEPENDENT SYSTEM OPERATOR.—The 

14 term ‘‘Independent System Operator’’ has the mean15 ing given the term in section 3 of the Federal Power 

16 Act (16 U.S.C. 796). 

17 (8) INTEGRATED RESOURCE PLANNING.—The 

18 term ‘‘integrated resource planning’’ means mod19 eling and evaluating how projected long-term elec20 tricity demands (such as electricity demands over pe21 riods of 5, 10, 20, or more years) within a service 

22 area can be met with a combination of electric gen23 eration resources that best achieve desired metrics, 

24 such as metrics relating to reliability, resilience, and 

25 cost. 


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1 (9) LOSS OF LOAD EXPECTATION; LOLE.— 

2 (A) IN GENERAL.—The term ‘‘loss of load 

3 expectation’’ or ‘‘LOLE’’ means the expected 

4 number of days per year that the available gen5 eration capacity is less than the system load for 

6 the applicable power grid region or service area. 

7 (B) CLARIFICATION.—As of November 

8 2023, a commonly acceptable value for loss of 

9 load expectation is 0.1 days per year, as de10 scribed in the standard of the North American 

11 Electric Reliability Corporation entitled ‘‘Plan12 ning Resource Adequacy Analysis, Assessment 

13 and Documentation’’ and numbered BAL–502– 

14 RF–03. 

15 (10) PLANNING RESERVE MARGIN.— 

16 (A) IN GENERAL.—The term ‘‘planning re17 serve margin’’ means the quotient, expressed as 

18 a percentage, obtained by dividing— 

19 (i) the difference between— 

20 (I) deliverable electric system 

21 supply capacity for a power grid re22 gion or service area; and 

23 (II) net demand in that power 

24 grid region or service area; by 


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1 (ii) net demand in that power grid re2 gion or service area. 

3 (B) CLARIFICATION.—As of November 

4 2023, a reserve margin falling within the range 

5 from 15 percent to 25 percent is typical for a 

6 power grid region or service area. 

7 (11) POWER GRID.—The term ‘‘power grid’’ 

8 means that portion of an Interconnection (as defined 

9 in section 215(a) of the Federal Power Act (16 

10 U.S.C. 824o(a))) that is located within the United 

11 States, including the relevant portion of each of the 

12 following: 

13 (A) The Eastern Interconnection. 

14 (B) The Western Interconnection. 

15 (C) The Texas Interconnection. 

16 (12) POWER GRID REGION.—The term ‘‘power 

17 grid region’’ means a geographic area— 

18 (A) located within a power grid; and 

19 (B) for which a regional entity (as defined 

20 in subsection (a) of section 215 of the Federal 

21 Power Act (16 U.S.C. 824o)) has enforcement 

22 authority under that section. 

23 (13) PROBABILISTIC MODELING.— 

24 (A) IN GENERAL.—The term ‘‘probabilistic 

25 modeling’’ means a modeling approach that 


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1 uses statistics to simulate and quantify the like2 lihood of achieving desired metrics, taking into 

3 consideration all modeled uncertainties, for de4 termination of the optimal resource portfolio, 

5 such as a modeling approach consistent with 

6 the document of the North American Electric 

7 Reliability Corporation entitled ‘‘Probabilistic 

8 Assessment Technical Guideline Document’’ 

9 and dated August 2016, including the rec10 ommendations described in that document. 

11 (B) INCLUSION.—The term ‘‘probabilistic 

12 modeling’’ includes modeling that can identify 

13 the most important parameters that impact a 

14 simulated metric for further characterization or 

15 optimization. 

16 (14) REGIONAL TRANSMISSION ORGANIZA17 TION.—The term ‘‘Regional Transmission Organiza18 tion’’ has the meaning given the term in section 3 

19 of the Federal Power Act (16 U.S.C. 796). 

20 (15) RELIABILITY STANDARD.—The term ‘‘reli21 ability standard’’ has the meaning given the term in 

22 section 215(a) of the Federal Power Act (16 U.S.C. 

23 824o(a)). 

24 (16) RESOURCE ADEQUACY.—The term ‘‘re25 source adequacy’’ means the adequate supply and 


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1 provision of electricity from various electric genera2 tion resources to meet projected electricity demands 

3 in a particular power grid region or service area. 

4 (17) SERVICE AREA.—The term ‘‘service area’’ 

5 means the area or region served by— 

6 (A) an electric utility; 

7 (B) a Regional Transmission Organization; 

8 or 

9 (C) an Independent System Operator. 

10 (18) STATE REGULATORY AUTHORITY.—The 

11 term ‘‘State regulatory authority’’ has the meaning 

12 given the term in section 3 of the Federal Power Act 

13 (16 U.S.C. 796). 

14 SEC. 3. PROBABILISTIC MODELING FOR BULK-POWER SYS15 TEM RESOURCE ADEQUACY MODELING AND 

16 INTEGRATED RESOURCE PLANNING. 

17 (a) IN GENERAL.—The Commission, pursuant to sec18 tion 215(d) of the Federal Power Act (16 U.S.C. 824o(d)), 

19 shall— 

20 (1) as soon as practicable after the date of en21 actment of this Act, order the Electric Reliability 

22 Organization to submit to the Commission, not later 

23 than 18 months after the date of that order, or as 

24 soon as practicable thereafter, 1 or more proposed 

25 reliability standards or modifications to reliability 


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1 standards to require, and ensure consistent methods 

2 (based on best-practices) for, the use of probabilistic 

3 modeling that includes consideration of key uncer4 tainties in generation, transmission, energy storage 

5 systems, and loads for resource adequacy modeling 

6 and integrated resource planning relating to the 

7 bulk-power system, reflecting the specific needs, re8 sources, and attributes of a given power grid region 

9 or service area; and 

10 (2) as soon as practicable after the submission 

11 of a proposed reliability standard or modification of 

12 a reliability standard under paragraph (1), approve 

13 the proposed reliability standard or modification in 

14 accordance with that section, if appropriate. 

15 (b) REQUIREMENTS.— 

16 (1) GENERATION.—With respect to generation, 

17 the reliability standards approved under subsection 

18 (a) shall require that probabilistic modeling for re19 source adequacy modeling and integrated resource 

20 planning shall include, to the maximum extent prac21 ticable, consideration of uncertainties relating to, as 

22 applicable for a given power grid region or service 

23 area— 

24 (A) the impact of distributed generation 

25 resources; 


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1 (B) degradation from aging (such as soil2 ing and degradation of photovoltaic modules 

3 and batteries); 

4 (C) planned and unplanned outages; 

5 (D) the impact of weather (such as solar 

6 irradiance, wind, precipitation, snowpack, and 

7 extreme temperatures) on conventional and dis8 tributed generation resources; 

9 (E) correlated outages (such as correlated 

10 outages due to winter storms, extreme heat, 

11 wildfires, and other extreme weather events); 

12 (F) costs of generation resources, including 

13 costs of acquired energy efficiency as a re14 source; and 

15 (G) other relevant generation uncertain16 ties, as determined by the relevant electric util17 ity, Regional Transmission Organization, Inde18 pendent System Operator, or State regulatory 

19 authority. 

20 (2) TRANSMISSION.—With respect to trans21 mission, the reliability standards approved under 

22 subsection (a) shall require that probabilistic mod23 eling for resource adequacy modeling and integrated 

24 resource planning shall include, to the maximum ex25 tent practicable, consideration of uncertainties relatVerDate Sep 11 2014 21:35 May 03, 2024 Jkt 049200 PO 00000 Frm 00009 Fmt 6652 Sfmt 6201 E:\BILLS\S4144.IS S4144

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1 ing to, as applicable for a given power grid region 

2 or service area— 

3 (A) the impact of weather (such as the im4 pact of temperature on transmission facilities, 

5 including line ratings); 

6 (B) congestion and thermal overload; 

7 (C) costs of new or modified transmission 

8 infrastructure; and 

9 (D) other relevant transmission uncertain10 ties, as determined by the relevant electric util11 ity, Regional Transmission Organization, Inde12 pendent System Operator, or State regulatory 

13 authority. 

14 (3) ENERGY STORAGE.—With respect to energy 

15 storage, the reliability standards approved under 

16 subsection (a) shall require that probabilistic mod17 eling for resource adequacy modeling and integrated 

18 resource planning shall include, to the maximum ex19 tent practicable, consideration of uncertainties relat20 ing to, as applicable for a given power grid region 

21 or service area— 

22 (A) round-trip efficiency; 

23 (B) battery capacity fade; 

24 (C) the impact of weather (such as the im25 pact of drought on pumped hydrologic storage); 


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1 (D) the impact of distributed energy stor2 age; 

3 (E) costs of energy storage; and 

4 (F) other relevant energy storage uncer5 tainties, as determined by the relevant electric 

6 utility, Regional Transmission Organization, 

7 Independent System Operator, or State regu8 latory authority. 

9 (4) LOADS.—With respect to loads, the reli10 ability standards approved under subsection (a) shall 

11 require that probabilistic modeling for resource ade12 quacy modeling and integrated resource planning 

13 shall include, to the maximum extent practicable, 

14 consideration of uncertainties relating to, as applica15 ble for a given power grid region or service area— 

16 (A) the impact of temperature and weath17 er, including extreme weather events, on loads; 

18 (B) the timing and changing mix of loads, 

19 including— 

20 (i) increased electrification of trans21 portation, including bidirectional charging 

22 and discharging of batteries used in elec23 tric vehicles; 


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1 (ii) increased electrification of home 

2 appliances, such as hot-water heaters and 

3 ovens, and space heating and cooling; and 

4 (iii) increased electrification of indus5 trial processes; and 

6 (C) other relevant electric-load uncertain7 ties, as determined by the relevant electric util8 ity, Regional Transmission Organization, Inde9 pendent System Operator, or State regulatory 

10 authority. 

11 (c) USE OF MODELING.—The reliability standards 

12 approved under subsection (a) shall require probabilistic 

13 modeling to be used, at a minimum— 

14 (1) to simulate and quantify desired metrics 

15 (such as loss of load expectation, expected unserved 

16 energy, effective load carrying capability (also known 

17 as ‘‘capacity value’’), planning reserve margin, and 

18 cost), taking into consideration the relevant uncer19 tainties described in subsection (b), to assist in the 

20 determination of the optimal resource portfolio for 

21 the applicable power grid region or service area; and 

22 (2) to identify the parameters and processes 

23 considered under subsection (b) that— 

24 (A) are the most important, in that they 

25 have the most impact on the magnitude or unVerDate Sep 11 2014 21:35 May 03, 2024 Jkt 049200 PO 00000 Frm 00012 Fmt 6652 Sfmt 6201 E:\BILLS\S4144.IS S4144

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1 certainty of the applicable simulated metrics; 

2 and 

3 (B) can be further characterized or opti4 mized to improve the modeling and determina5 tion of the optimal resource portfolio for the ap6 plicable power grid region or service area. 

7 (d) EXISTING APPROACHES; STATE REQUIRE8 MENTS.— 

9 (1) IN GENERAL.—The reliability standards ap10 proved under subsection (a)— 

11 (A) shall take into consideration, and shall 

12 allow for the continued use of, any probabilistic 

13 modeling in use by an electric utility, a Re14 gional Transmission Organization, or an Inde15 pendent System Operator as of the date of en16 actment of this Act; and 

17 (B) shall not preempt, or exempt any elec18 tric utility, Regional Transmission Organiza19 tion, or Independent System Operator from 

20 compliance with, any probabilistic modeling re21 quirement under State law. 

22 (2) REQUIREMENTS.—To the maximum extent 

23 practicable, the reliability standards approved under 

24 subsection (a) shall allow for compliance with those 

25 reliability standards to be achieved— 


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1 (A) in a manner consistent with— 

2 (i) the probabilistic modeling de3 scribed in subparagraph (A) of paragraph 

4 (1); and 

5 (ii) any requirements described in 

6 subparagraph (B) of that paragraph; and 

7 (B) by demonstrating— 

8 (i) the use of probabilistic modeling in 

9 accordance with subparagraph (A) or (B) 

10 of that paragraph; and 

11 (ii) that the probabilistic modeling 

12 adequately reflects, or has been modified 

13 or used in a manner to adequately reflect, 

14 the requirements described in subsections 

15 (b) and (c). 

Æ 


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