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Massachusetts' 2026 Clean Peak Standard Recalibration: Adaptation and Storage Tradeoffs

Yuhan Dai, Boyu Yao

arXiv:2609.36468v1eess.SYcs.SY

TL;DR

The combined effect of lower CPS minimum standards and expanded storage-multiplier eligibility on endogenous investment, physical clean-peak operation, and system cost had not been evaluated. An hourly capacity-expansion analysis compares pre- and post-May 2026 policy pathways, assessing how the combined recalibration affects endogenous battery expansion, physical clean peak discharge, peak-period fossil generation, and total system cost. 53.1% fewer new battery additions and 3.7% lower modeled system cost accompany a 30.4% decline in CPS-eligible discharge and an 11.7% increase in fossil generation during CPS hours.

  • Problem

    The combined effect of lower CPS minimum standards and expanded storage-multiplier eligibility on endogenous investment, physical clean-peak operation, and system cost had not been evaluated.

    Source: §I · p. 2

  • Method

    An hourly capacity-expansion analysis compares pre- and post-May 2026 policy pathways, assessing how the combined recalibration affects endogenous battery expansion, physical clean peak discharge, peak-period fossil generation, and total system cost.

    Source: §I · p. 2

  • Results

    53.1% fewer new battery additions and 3.7% lower modeled system cost accompany a 30.4% decline in CPS-eligible discharge and an 11.7% increase in fossil generation during CPS hours.

    Source: §IV · p. 6

  • Takeaways & Limitations

    The recalibration lowers the modeled storage requirement and cost while weakening physical clean-peak performance, even as certificate production is preserved more effectively than discharge.

    Source: §IV · p. 6

Abstract

from arXiv · show

Massachusetts recalibrated its Clean Peak Standard (CPS) in 2026 by lowering the minimum standards and expanding the Near-Term Resource Multiplier for qualifying storage. This paper evaluates the change using a three-zone, hourly capacity expansion model for 2026--2030. Both scenarios achieve full CPS compliance, but the post-May scenario reduces new battery additions by 53.1% and modeled system cost by 3.7%. CPS-eligible discharge declines by 30.4%, while Clean Peak Energy Certificate production declines by only 9.5%. Fossil generation during CPS hours increases by 11.7%, whereas modeled emissions remain nearly unchanged because the Regional Greenhouse Gas Initiative cap binds. The recalibration therefore lowers the modeled storage capacity requirement while weakening physical clean-peak performance.

F GEN

The model’s parameter and variable definitions specify resource availability and storage efficiency, adequacy and CPS requirements, and cost and operating quantities.

F GEN

  • Renewable availability factors and storage charging and discharging efficiencies are defined as unitless model parameters.Source: F GEN · p. 1

F ELCC

  • Technology ELCC factors and the resource-adequacy planning reserve are unitless, as is the annual CPS minimum compliance percentage.Source: F ELCC · p. 1

M CPS

  • The hourly CPS multiplier and storage Near-Term Resource Multiplier are defined as unitless parameters.Source: M CPS · p. 1, M NTRM · p. 1

P CPS

  • The CPS Alternative Compliance Payment is denominated in dollars per CPEC.Source: P CPS · p. 1

P CO2

  • The RGGI allowance price is denominated per short ton of CO2, while unit investment and operating costs are also specified.Source: P CO2 · p. 1
  • The model defines generation, power flow, load shedding, storage charging and discharging, state of charge, adequacy and CPS shortfalls, and investment and operating-status variables.Source: P CO2 · p. 1

I. INTRODUCTION

The introduction frames the CPS recalibration as a test of whether revised certificate obligations can balance near-term policy feasibility with physical clean-peak benefits. The paper compares the pre- and post-May pathways using an hourly capacity-expansion analysis.

  • The CPS rewards eligible generation, storage discharge, and demand reduction during high-net-demand periods through CPECs and seasonal, hourly, and monthly-peak multipliers.Source: §I · p. 2
  • The May 2026 amendments lowered CPS minimum standards and extended NTRM eligibility for qualifying delayed projects, with a stated aim of reducing near-term ratepayer exposure while preserving a storage-deployment pathway.Source: §I · p. 2
  • The policy tradeoff is that lower minimum standards reduce CPEC demand while expanded multiplier eligibility increases certificates per qualifying discharged MWh without directly increasing physical storage or displacement.Source: §I · p. 2
  • Prior work did not evaluate how the combined change affects endogenous battery expansion, clean-peak discharge, peak-period fossil generation, and total system cost.Source: §I · p. 2
  • The study compares the two policy pathways in a three-zone, hourly 2026–2030 model evaluating investment, operation, compliance, adequacy, emissions, and cost.Source: §I · p. 2

II. STUDY SCOPE AND MODEL DESCRIPTION

The study models Massachusetts as a three-zone system over 2026–2030, jointly optimizing candidate investment and hourly operations. Its two scenarios compare the pre-May policy trajectory with the May 2026 package.

A. Study Scope and Policy Scenarios

B. Multi-Stage Capacity Expansion Model

The multi-stage model minimizes costs over the planning horizon, combining annualized investment with operating and policy-related costs. Its operating-cost terms include generation, storage, reliability, CPS, and emissions-related components.

1) Objective Function:

2. Operating cost Cop

  • Operating costs include fixed O&M, variable generation, and battery charging and discharging; policy and penalty costs include unserved energy, adequacy and CPS shortfalls, and RGGI allowances.Source: §2 · p. 3
  • All monetary terms are expressed in consistent annual dollars and summed across modeled years.Source: §2 · p. 3

2) System Operation and Expansion Constraints:

The constraints govern hourly generation and load balance, capacity additions, and storage operation. Storage state of charge is linked chronologically across the model year, while load shedding is bounded by zonal load.

2) System Operation and Expansion Constraints:

  • Thermal and renewable output are limited by available capacity, with renewable generation also restricted by hourly availability.The hourly zonal power balance includes generation, storage, interzonal transfers, and load shedding.Source: 2) System Operation and Expansion… · p. 3
  • Candidate additions are tracked cumulatively by year, while existing capacity is preserved.Load shedding is bounded by zonal load.Source: 2) System Operation and Expansion… · p. 3
  • Storage power and energy limits are combined with chronological state-of-charge evolution across all 8760 hours, with initial and terminal levels fixed at 50% of available energy capacity.The preceding-period index includes transitions between consecutive days.Source: 2) System Operation and Expansion… · p. 3

3) Massachusetts Policy Compliance Constraints:

The compliance constraints cover resource adequacy, annual emissions from RGGI-covered generators, and annual CPS obligations. Adequacy is assessed on a net-load basis, and CPS shortfalls can be covered through ACPs.

3) Massachusetts Policy Compliance Constraints:

A. Data Sources and Assumptions

The model represents Massachusetts as three zones and uses forecasted and queued resources, net-load demand, and hourly renewable availability. Its CPS and technology assumptions are paired with operational omissions intended to isolate capacity-expansion and dispatch effects.

A. Data Sources and Assumptions

  • The three-zone system comprises NEMA, SEMA, and WCMA, with existing resources from the ISO-NE CELT forecast and candidate batteries and offshore wind from the interconnection queue.Candidate capacities are continuously divisible; transfer limits use ISO-NE interface capability assumptions.Source: A. Data Sources and Assumptions · p. 4
  • Hourly demand is based on the 2025 Massachusetts load profile, scaled through 2030, with imports deducted and annual net load used as a proxy for CPS-obligated retail sales.Weather-based renewable availability profiles and the full 8760-hour chronology are used.Source: A. Data Sources and Assumptions · p. 4
  • Technology costs use national projections, annualized over assumed lifetimes at a 6% discount rate; the model also assumes four-hour batteries and an 11% planning reserve margin.Battery efficiencies are 95%, and the annual RGGI cap is 6.17 million tons with a $27.60/ton allowance price; CPS ACP is $65/CPEC.Source: A. Data Sources and Assumptions · p. 4
  • New-storage NTRM is 1 pre-May and 2 post-May; eligible discharge earns seasonal multipliers in designated business-day peak periods and 25 at the actual monthly system peak.Other discharge receives no CPEC credit; Table II summarizes the hourly CPS multipliers.Source: A. Data Sources and Assumptions · p. 4, Table II · p. 4
  • The model omits unit commitment, start-up and minimum-generation constraints, ancillary-service revenues, endogenous imports, and resource retirements.Existing units remain available throughout the horizon, and each zonal battery may charge and discharge simultaneously; these assumptions isolate capacity-expansion and dispatch effects rather than reproduce all ISO-NE market operations.Source: A. Data Sources and Assumptions · p. 4

B. Numerical Results

Both policy scenarios meet annual CPS requirements, while the post-May scenario uses less storage and physical discharge than the decline in certificate production. Its dispatch remains strongest during the monthly peak hour, but CPS-hour fossil generation increases while the binding RGGI cap keeps modeled emissions nearly unchanged.

B. Numerical Results

  • Resource adequacy shortfall and load shedding are zero in every year, and no offshore wind is selected because its modeled cost is not justified without unserved energy or binding adequacy constraints.The comparison is therefore driven primarily by battery capacity and operation.Source: B. Numerical Results · p. 4

1) Deployment Burden and Certificate Leverage:

2) Dispatch Response Across CPS Multipliers:

  • At M CPS = 25 both scenarios reach full available capacity; at M CPS = 1 frequency falls from 0.896 to 0.783 and depth from 0.854 to 0.796, while M CPS = 4 depth falls from 0.968 to 0.882.Frequency is the share of category hours with positive aggregate BSS discharge; depth is average output during those hours as a share of available BSS power capacity.Source: 2) Dispatch Response Across CPS… · p. 5
  • 11.7% more cumulative fossil generation during CPS hours accompanied a five-year CO2 emissions change of only −0.02% as the RGGI cap bound from 2027 onward.Redispatch in other hours offset the additional CPS-period fossil generation.Source: 2) Dispatch Response Across CPS… · p. 5

3) Cost and Physical Clean-Peak Tradeoffs:

The post-May scenario lowers modeled system cost and battery additions while preserving full CPS compliance, but CPS-eligible discharge and fossil displacement during CPS hours decline. The results reflect the combined changes to minimum standards and NTRM, and model system effects rather than project delivery under real-world constraints.

3) Cost and Physical Clean-Peak Tradeoffs:

IV. CONCLUSION

  • Certificate production is maintained more effectively than physical discharge and fossil displacement during CPS periods.Source: 3) Cost and Physical Clean-Peak… · p. 5, §IV · p. 6
  • New BSS additions fall from 1.372 to 0.643 GW post-May, while full CPS compliance is maintained.The post-May scenario reduces modeled system cost by 3.7%.Source: §IV · p. 6
  • CPS-eligible discharge falls by 30.4% and fossil generation during CPS hours rises by 11.7%, while modeled emissions remain nearly unchanged under the binding RGGI cap.Source: §IV · p. 6
  • The recalibration lowers the modeled storage capacity requirement, but the combined minimum-standard and NTRM changes constrain attribution to either policy change alone.Results are modeled system effects, not project delivery under permitting, procurement, equipment, or interconnection constraints.Source: 3) Cost and Physical Clean-Peak… · p. 5, §IV · p. 6
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