Resource Adequacy

  • Practices and Standards

Practices and Standards

Reliability Targets Explained 

Although systems could aim for “perfect” reliability, that is setting a loss of load probability of 0.0, this is not practical nor cost-effective in reality. A commonly used adequacy target is 1 day in 10 years loss of load expectation.

Certain utilities use a target of 0.1 day/year instead of 1d/10y LOLE. However, it is useful to point out that these targets are not the same. Consider a 10-year time period, and a system that achieves 0.1d/y. This means that in any year, we would expect 0.1 days of outage; therefore, in 10 years, one would reasonably expect 10 outage days (one per year). By contrast, 1d/10y means that, of the 10 years, 9 of them have no outages. The difference between these two targets is shown in the figure on the right. Both timelines extend for 10 years. The upper timeline illustrates a single event during the 10-year period, whereas the lower timeline shows small outages in each of the 10 years.

RA Metrics event comparison

Graphical depiction of the difference between 0.1 days per year and 1 day per 10 years.

Regional Standards

Metrics are based on information available in 2021 - 2022 for all tables

North America

In the North American bulk power system, most regions rely on the 0.1 days/year LOLE, which is also known as the one-event-in-ten-years RA standard, and have done so for many decades [1 ]. In general, the 0.1 days/year LOLE standard translates to more than a 10% planning reserve margin [2]. In addition to a system-wide planning reserve margin of 15%, California has local and flexibility RA requirements. The local RA requirement is determined using the 1-in-10 weather year and an N-1-1 contingency, which represent the minimum resources needed if the two largest contingencies fail within thirty minutes of each other. The flexibility RA requirement is determined based on comparing the largest three-hour ramp for each month to the three-hour ramp capability of resources that are qualified to bid into the market as flexible. In Hawaii, adequacy is assessed in resource planning studies using the Energy Reserve Margin (ERM) targets of 30% for Oahu, Hawaii, and Maui islands, and 60% for Molokai and Lanai islands.

Metrics North America
Country or Region RA MetricsCriteria Entity Calculating RA Metric
North America [1],[2]
MISO LOLE ≤ 0.1 days/year MISO
MRO-Manitoba Hydro LOLE ≤ 0.1 days/year Manitoba Public Utilities Board
NPCC-Maritimes LOLE ≤ 0.1 days/year Maritimes Sub-areas and NPCC
NPCC-New England LOLE ≤ 0.1 days/year ISO-NE and NPCC
NPCC-New York LOLE ≤ 0.1 days/year NYSRC and NPCC
NPCC-Ontario LOLE ≤ 0.1 days/year IESO and NPCC
NPCC-Québec LOLE ≤ 0.1 days/year Hydro-Québec and NPCC
PJM Interconnection LOLE ≤ 0.1 days/year PJM Board of Managers
SERC-C LOLE ≤ 0.1 days/year Member Utilities
SERC-E LOLE ≤ 0.1 days/year Member Utilities
SERC-FP LOLE ≤ 0.1 days/year Florida Public Service Commission
SERC-SE LOLE ≤ 0.1 days/year Member Utilities
SPP LOLE ≤ 0.1 days/year SPP RTO Staff and Stakeholders
TRE-ERCOT 1 LOLE ≤ 0.1 days/year ERCOT Board of Directors
WECC-AB LOLP 2 ≤ 0.02% WECC
WECC-BC LOLP ≤ 0.02% WECC
WECC-NWPP-US & RMRG [3] LOLE ≤ 0.1 days/year WECC
WECC-SRSG LOLP ≤ 0.02% WECC
WECC-CAMX [4] PRM ≥ 15% CPUC
Additional local and flexible RA requirements
Hawaii [5] ERM ≥ 30% (3 islands), 60% (2 islands) HECO

 

1 LOLE is reported as a guideline metric and not as a requirement in the ERCOT system, which relies on energy only and scarcity pricing to meet RA needs. 
2The LOLP metrics for the WECC represent an event-period of 1 day and a horizon of 10 years.
 

[1] J. P. Pfeifenberger, K. Spees, K. Carden, and N. Wintermantel. “Resource Adequacy Requirements: Reliability and Economic Implications.” September 2013.
[2] North American Electric Reliability Corporation. “2020 Long-Term Reliability Assessment.” December 2020.
[3] Northwest Power Pool. “NWPP Resource Adequacy Program - Detailed Design.” July 2021.
[4] California Public Utilities Commission. “Resource Adequacy Homepage."
[5] Hawaiian Electric Company, Inc. “Adequacy of Supply.” January 29, 2021.

Europe

In Europe, many countries use the LOLH metric, which ranges from 3–8 hours/year. Belgium’s power system requires an LOLH95 of less than 20 hours/year, in addition to maintaining an LOLH of less than 3 hours/year. LOLH95 represents the LOLH at the 95th percentile of the cumulative density function of the needed LOLH. Accounting for LOLH95 inserts tail events into the definition of RA. Tail events may become more important as power systems become more exposed to events driven by climate change. In Spain, island grids require an LOLE of one day in 10 years, while mainland Spain operates according to a 10% planning reserve margin requirement.

Metrics Europe
Country or RegionRA MetricsCriteriaEntity Calculating RA Metric
Europe [6,7]
Belgium [8]LOLH ≤ 3 hours/yearElia Group
LOLH953 ≤ 20 hours/year
France [9]LOLH ≤ 3 hours/yearRTE
Great Britain [10]LOLH ≤ 3 hours/yearNational Grid ESO
Ireland and Northern Ireland [11]LOLH ≤ 8 hours/year (Ireland)EirGrid and SONI
LOLH ≤ 4.9 hours/year (Northern Ireland)
Netherlands [12]LOLH ≤ 4 hours/yearTenneT
Poland [13]LOLH ≤ 3 hours/yearPSE
Portugal [14]LOLH ≤ 5 hours/yearREN
Spain [14,15]PRM ≥ 10% (Mainland)REE
LOLE ≤ 1 day in 10 years (Island grids)

 

3 This is known as LOLE95 in Belgium to cover load for a statistically abnormal year. This has been modified to LOLH95 here for consistency; units are in hours per year, rather than days per year.

[6] M. Poncela Blanco, A. Spisto, N. Hrelja, and G. Fulli. “Generation Adequacy Methodologies Overview.” European Commission Joint Research Centre, September 2016.
[7] European Commission. “Identification of Appropriate Generation and System Adequacy Standards for the Internal Electricity Market – Final Report.” EC Directorate-General for Energy, Brussels, 2016.
[8] Elia Group. “Adequacy and Flexibility Study for Belgium 2022-2032.” 2021.
[9] Wind Europe. “Assessing Resource Adequacy in an Integrated EU Power System.” June 2016.
[10] National Grid ESO. “National Grid ESO Electricity Capacity Report.” May 31, 2020.
[11] Eirgrid and SONI. “All-Island Generation Capacity Statement 2021-2030.” 2021.
[12] TenneT. “Adequacy analyses voor scenario’s met vervroegde (tijdelijke) sluiting van kolencentrales in Nederland.” February 24, 2020.
[13] Polskie Sieci Elektroenergetyczne. “Development Plan for meeting the current and future electricity demand for 2021-2030.” 2020.
[14] Wind Europe. “Assessing Resource Adequacy in an Integrated EU Power System.” June 2016.
[15] Ministerio de Industria, Energía y Turismo. “Planificación Energética. Plan de Desarrollo de la Red de Transporte de Energía Eléctrica 2015 – 2020.” 2015. 

Oceania

In Oceania, two countries are reported. In Australia, the National Electricity Market (NEM), which covers the vast majority of Australia’s total load, assesses the adequacy of the power system based on 0.002% NEUE. The smaller Australia winter energy margin (WEM), which covers southwest Western Australia, requires a reserve margin that is calculated as the greater of 7.6% of the one-in-ten years forecast peak demand plus the intermittent load allowance or the capacity of the largest generating unit. In New Zealand, the supply standards include a WEM of greater than or equal to 14–16% on a national level, a WEM of greater than or equal to 25.5 to 30% for the South Island, and a winter capacity margin (WCM) of greater than or equal to 630 to 780 MW for the North Island.

Oceania
Country or Region RA MetricsCriteria Entity Calculating RA Metric
Oceania
Australia-NEM [16] NEUE ≤ 0.002% per region AEMO
Australia-NT [17] NEUE ≤ 0.002%  AEMO
Australia-WEM [18] PRM ≥ WEM metric 4 AEMO
NEUE ≤ 0.002%
New Zealand [19,20] WEM ≥ 14-16% (New Zealand) Transpower
WEM ≥ 25.5-30% (South Island)
WCM ≥ 630-780 MW (North Island)

4 The WEM metric for PRM is calculated as the greater of 7.6% of the one-in-ten year forecast peak demand plus an intermittent load allowance or the capacity of the largest generating unit. An intermittent load is normally fully served by embedded generation and only requires electricity from the grid when its embedded generator is not operating.

[15] Ministerio de Industria, Energía y Turismo. “Planificación Energética. Plan de Desarrollo de la Red de Transporte de Energía Eléctrica 2015 – 2020.” 2015.
[16] Australian Energy Market Operator. “2021 Electricity Statement of Opportunities, A report for the National Electricity Market.” August 2021.
[17] Utilities Commission of the Northern Territory. “Northern Territory Electricity Outlook Report.” 2020.
[18] Australian Energy Market Operator. “2021 Electricity Statement of Opportunities, A Report for the Wholesale Electricity Market.” June 2021.
[19] Transpower New Zealand Limited. “Security of Supply Annual Assessment 2020.” April 2020.
[20] New Zealand Electricity Authority. “Electricity Industry Participation Code.” 2010.

Africa

In South Africa, Eskom performs a RA assessment of the country based on three system adequacy metrics. The first metric requires the unserved energy to be less than 20 GWh per year. The second metric requires the combined capacity factor of the open-cycle gas turbine (OCGT) plant in operation to be less than 6% per year. The third metric requires the capacity factor of a contingency coal-fired baseload station to be less than 50% per year.

Metrics Africa
Country or RegionRA MetricsCriteriaEntity Calculating RA Metric
Africa
South Africa [21]EUE < 20 GWh/yearEskom
OCGT capacity factor 5 < 6%/year
Baseload stations capacity factor 6 < 50%/year

5 This is the combined capacity factor of the open-cycle gas turbine (OCGT) plant in operation in a year.
6 This is the capacity factor of a contingency coal-fired baseload station in a year.

[21] Fabricius, N. Sigwebela, S. Damba, P. Rambau, D. Magapa, and S. Makopo, “Medium-Term System Adequacy Outlook 2020.” October 30, 2020.

Asia

In Asia, most of the countries for which publicly available information was found use either PRM or LOLH for RA standards. The PRM metric ranges from 8% to 30%, while LOLH ranges from 3 to 12 hours/year. India uses a NEUE of less than or equal to 0.05%, in addition to its LOLP standard. Malaysia requires an LOLE metric of 1 day/year.

Asia Metrics
Country or Region RA MetricsCriteria Entity Calculating RA Metric
Asia
India [22] LOLP 7 ≤ 0.2% CEA
NEUE ≤ 0.05%
Indonesia [23] PRM (2019-2028) ≥ 30% (National) Ministry of Energy and Mineral Resources
Japan [24] PRM (2020-2029) ≥ 8% per region OCCTO
Laos [25] PRM (2020-2030) ≥ 15% Ministry of Energy and Mines
Malaysia [26] LOLE ≤ 1 days/year TNB
Philippines [27] PRM (2017-2040) ≥ 25% DOE
Singapore [28]up> LOLH ≤ 3 hours/year EMA
Thailand [30]up> PRM (2015-2036) ≥ 15% EGAT
Vietnam [32] LOLH ≤ 12 hours/year per region MOIT

7 The LOLP metric for India represents an event-period of 1 hour and a horizon of 1 year.

[22] Central Electricity Authority. “National Electricity Plan.” January 2018.
[23] Asian Development Bank. “ADB-PLN Electrical Grid Strengthening Program: Ongoing and Planned Support.” February 23, 2021.
[24] Organization for Cross-regional Coordination of Transmission Operators, Japan. “Aggregation of Electricity SupplyPlans, Fiscal Year 2020.” June 2020.
[25] Xaiyalath. “Power Development Plan 2020-2030 of Lao PDR.” Ministry of Energy and Mines, January 28, 2020.
[26] Tenaga Nasional Bhd. “Third Regulatory Period for Electricity Sector.” October 26, 2020.
[27] A. Bariso. “Philippine Energy Plan 101.” Department of Energy, October 30, 2018.
[28] Energy Market Authority. “Determining the Required Reserve Margin to Maintain a Reliable Electricity Supply in Singapore.”
[29] Energy Market Authority. “Singapore Electricity Market Outlook (SEMO) 2020.” December 30, 2020.
[30] Electricity Generating Authority of Thailand. “The approval of Thailand Power Development Plan.” August 24, 2012.
[31] International Energy Agency. “Thailand Electricity Security Assessment.” April 14, 2016.
[32] USAID V-LEEP. “Technical Report: Impact Analysis of Integrating Significant Renewable Energy in Vietnam’s Power Sector:A PLEXOS-based Analysis of Long-term Power Development Planning.” March 18, 2021.

Middle East

Certain countries in the Middle East implement planning reserve margins for adequacy and have lower values for these compared to other regions globally. The PRM in Qatar is 6% and 8-10% in Saudi Arabia. In Oman, the LOLH standard of 24 hours/year is relatively higher than in other countries worldwide. The Gulf Coordinating Council Interconnection Authority (GCCIA) operates the interconnection between Oman, Qatar, Saudi Arabia, Bahrain. Kuwait, and United Arab Emirates, and has a 5 hours/year LOLH criterion for the entire region, which is then allocated to member states based on peak load.

Middle East Metrics
Country or Region RA MetricsCriteria Entity Calculating RA Metric
Middle East
Saudi Arabia [33] PRM (2016) ≥ 8-10% SEC
Oman [34] LOLH ≤ 24 hours/year OPWP
Qatar [35] PRM (2019) ≥ 6% KAHRAMAA

[33] O. I. Asiri, Y. A. Alturki, M. S. Al-Saud, and M. A. El-kady. “Reliability Evaluation of Riyadh System Incorporating Renewable Generation.” November 2016.
[34] Oman Power and Water Company. “7-Year Statement, Issue 13 (2019 – 2025).” 2019.
[35] International Renewable Energy Agency. “Power Sector Planning in Arab Countries: Incorporating Variable Renewables.” April 21-24, 2019.

The purpose of this site is to bring together information to help those trying to assess resource adequacy. It draws on a wide range of work that EPRI and the industry has conducted in response to the challenges arising as power systems evolve. We welcome your feedback and suggestions to make this website increasingly useful to support you and your decisions.

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