1. Compare and Contrast ELCC Methodologies Across CPUC Proceedings

2. Why Use ELCC?
California currently uses a time-window approach to value the capacity contribution of renewable resources
Net qualifying capacity is based on the 30th percentile of renewable production during specified peak time window (2-6 pm, June-Sept.)
Most utilities and ISOs across the country use similar heuristics
Heuristic approaches have the benefit of simplicity but are not as accurate as a reliability-based approach
ELCC measures resource contributions across year, not just in peak period
Inaccuracies of heuristics are magnified as renewable penetration increases
California Senate Bill 2 (2011) requires use of ELCC
“…the commission shall determine the effective load carrying capacity of wind and solar energy resources on the California electrical grid. The commission shall use those effective load carrying capacity values in establishing the contribution of wind and solar energy resources toward meeting the resource adequacy requirements established pursuant to Section 380.”
As the penetration of must-take resources increases, studies show the system is stressed at times other than Summer peak, so evaluating the whole year becomes more important

3. Factors that Affect the Marginal Capacity Value of Renewable Generation
Coincidence with load
Locations with better solar resources and more production later in the day will have higher ELCC values
Production variability
The potential for low production when energy is needed and/or high production when energy is not needed reduces the value of a resource
Location
Distributed resources may avoid transmission and distribution losses
Existing quantity of variable generation
Common resource types should show diminishing marginal returns, each additional unit of variable generation has less capacity credit than the previous unit
Also note: the ability to vary output to match load increases value of a resource (so a “non-responsive” resource has a lower relative value)

4. ELCC Value in Application
Stakeholders have suggested multiple potential links between ELCC figures determined in RA and the RPS Calculator:
Direct use of RA’s ELCC numbers
Use of same technology categories as RA
The portfolio capacity value is a relevant calculation for resource planning
Due to the complementarity of different resources the portfolio value will be higher than the sum of each individual resource measured alone
May need to attribute the portfolio capacity value to individual resources
E.g., allocate RA procurement responsibility among multiple entities
There are many options, but no standard or rigorous way to do this
The marginal capacity value, which considers the existing portfolio, should be used in procurement
This value will change over time with the mix of system needs & resources
Individual Solar Capacity Value
Combined Capacity Value
Individual Wind Capacity Value

5. Renewable ELCC Values are Needed in Three CPUC Proceedings
Values are used for a different purpose in each proceeding
Resource Adequacy
ELCC is used to assign capacity credit to renewable resources for RA procurement
Calculate portfolio wide ELCC and allocate to individual projects
Short-term focus: years out
Historical data from resources in the ground
Model: SERVM
LTPP
Establishes total renewable capacity contribution to calculate residual system need
Calculate portfolio wide ELCC-based capacity contribution
Long-term focus: years out
Need historical and projected data
Model: SERVM and RPS Calculator
RPS Procurement
Estimates contribution from new resources in order to inform renewable procurement
Marginal contribution from new resource depends on portfolio
Long-term focus: years out
Need historical and projected data
Model: Utility models

6. ELCC Process Flow Chart
RPS Procurement
Utilities look out 20 years and procure RPS energy
Requires forecast of ELCCs that will be used in RA proceeding
RPS Calculator
RPS Calculator fills in with generic projects to reach RPS target
Requires forecast of ELCCs used in RA proceeding
Other CPUC Proceedings
Use system-wide ELCC- derived values at future penetrations to value demand-side programs based on their specific characteristics
Energy Efficiency
Demand Response
Load Shifting
Energy Storage
Distributed PV
Resource Adequacy
RA calculates actual NQC to apply to each renewable project
Only considers existing portfolio
LTPP
Uses values from RA for existing resources and RPS Calculator for new renewable resources
Evaluates alternative mitigation strategies for reliability issues
LTPP; Evaluates alternative mitigation strategies for reliability issues; Also used in IOU procurement process

7. Use of ELCC in RA Proceeding
Principal purpose: Establish near-term system capacity procurement obligations for regulated load-serving entities (LSEs)
Scale of calculation: requires calculation of the capacity value attributed to existing individual renewable energy projects in each LSE’s portfolio
General method: Calculate system-wide ELCC using an LOLP model and allocate to individual projects
Time period: Near-term (1-3 years out)
Data required: historical performance of existing resources
Model used: SERVM

8. Use of ELCC in LTPP Proceeding
Principal purpose: Develop multiple alternate resource portfolios to address any identified long-term system reliability needs
Scale of calculation: requires calculation of the capacity value attributed to the entire portfolio of existing and forecasted resources and proposed reliability mitigations
General method: Calculate system-wide total capacity contribution using an LOLP model; individual ELCCs not needed but may be helpful for allocation of system need
Time period: Long-term (5-20 years out)
Data required: historical performance of existing resources and projected performance of new resources
Model used: not determined at this time
LTPP looks at all facets of reliability: over-generation, peak reliability, local peak reliability, system stability, the need for flexible resources, etc.

9. Use of ELCC in RPS Procurement
Principal purpose: Procure least-cost mix of renewable resources when considering net portfolio value
Scale of calculation: Requires calculation of the marginal capacity value associated with potential new renewable energy projects
General method: Calculate marginal contributions of new renewable resource types using an LOLP model, given procurement that has already occurred in the CAISO system
Time period: Long-term (5-20 years out)
Data required: historical performance of existing resources and projected performance of new resources
Model used: Utilities can develop or procure models

10. Summary
ELCC values are used for different purposes in different CPUC proceedings
Different types of values are used for each proceeding
RA: Historical values for each existing resource
LTPP and RPS Procurement: Forecasted values for potential future resources
It may not be practical to use a single model to calculate all of the ELCC values that are needed
However, the models should be in general alignment about the marginal value of different resources at various penetrations
It may be useful to conduct a benchmarking exercise when all models are available and ready for use