CAISO Costs & Deliverability

Cost Summary — Cluster 14 Pre-Assessment

$67k

IFS / MW at GIA signing

$120–180k

Estimated NUC/MW (Cluster 14)

$5–50M

Typical Phase II direct cost

300 days

Phase II study window

Shared — Phase I

Network Upgrade Costs (NUC)

Identified during the cluster Phase I study. Allocated proportionally to triggering projects by load-flow contribution (sensitivity factors). Typical cluster-wide NUC range: $50–$300M per cluster. Not assigned to individual projects until Phase II allocation.

CAISO BPM-CG-012 §7.6

Direct — Phase II

Interconnection Facilities Study (IFS) Costs

Substation equipment, protection upgrades, generation lead lines directly assigned to each project. Costs vary by distance to POI, voltage level, and required TO equipment. Typical range: $5–50M per project. Actuals reconciled after construction.

CAISO BPM-CG-012 §8.4

Optional Election

TPD — Transmission Planning & Deliverability

Projects electing Full Capacity Deliverability Status (FCDS) pay an additional TPD cost allocation to fund deliverability-enabling upgrades. Energy-Only projects avoid TPD costs entirely but cannot count MW toward CPUC Resource Adequacy requirements.

CAISO Tariff, Appendix DD §8.9

Security Deposit

Interconnection Financial Security (IFS)

$67,000/MW posted at GIA execution. Milestone-based reduction schedule — IFS decreases as M1–M5 milestones are achieved. Fully refunded 30 days after commercial operation, net of any cost overruns from actual vs. estimated study costs.

CAISO Tariff §16.6; FERC Order 2023

Cost Benchmarks by Technology

Technology	Avg Phase I NUC ($/MW)	Avg Phase II Direct Cost	IFS Requirement	TPD Cost Range
Utility Solar (standalone)	$35,000–$80,000/MW	$8–30M	$67k/MW	$20–120M
Solar + BESS (co-located)	$45,000–$120,000/MW	$10–40M	$67k/MW (combined AC)	$25–150M
Standalone BESS (≥4 hr)	$25,000–$60,000/MW	$5–20M	$67k/MW	$15–90M
Offshore Wind (floating)	Est. $150,000–$300,000/MW	$50–200M	$67k/MW	Under study
Geothermal	$80,000–$200,000/MW	$15–60M	$67k/MW	$30–120M
Small Gen (≤20 MW)	Reduced — fast track	$1–8M	$67k/MW	N/A (below threshold)

Technology

Avg Phase I NUC ($/MW)

Avg Phase II Direct Cost

IFS Requirement

TPD Cost Range

Utility Solar (standalone)

$35,000–$80,000/MW

$8–30M

$67k/MW

$20–120M

Solar + BESS (co-located)

$45,000–$120,000/MW

$10–40M

$67k/MW (combined AC)

$25–150M

Standalone BESS (≥4 hr)

$25,000–$60,000/MW

$5–20M

$67k/MW

$15–90M

Offshore Wind (floating)

Est. $150,000–$300,000/MW

$50–200M

$67k/MW

Under study

Geothermal

$80,000–$200,000/MW

$15–60M

$67k/MW

$30–120M

Small Gen (≤20 MW)

Reduced — fast track

$1–8M

$67k/MW

N/A (below threshold)

CAISO Deliverability Elections

Most Common

Full Capacity Deliverability Status (FCDS)

Project can count full MW toward CPUC and CEC Resource Adequacy requirements. Requires passing a Transmission Planning and Deliverability study. Preferred by California LSEs purchasing RA capacity. Approximately 80% of CAISO queue applicants elect FCDS.

CAISO Tariff §40.4

Compromise

Partial Capacity Deliverability Status (PCDS)

Some MW count toward RA, remainder qualifies as energy-only. Occurs when TPD study identifies binding transmission limitations at the proposed delivery point. Developer can elect to pay incremental upgrade cost to achieve full FCDS instead.

CAISO Tariff §40.4.1

Merchant / Export

Energy-Only (EO) Interconnection

Project receives interconnection service but cannot count toward California RA. No TPD assessment required — faster path to commercial operation. Common for out-of-state PPA developers, merchant solar, or projects targeting WA/OR markets. Lower IFS risk profile.

CAISO Tariff §40.4.2

Cost Allocation

Network Upgrade Cost Responsibility

Under FERC Order 2023, CAISO uses first-mover cost assignment: projects that trigger a specific upgrade bear the direct cost. Shared cluster upgrades allocated by load-flow sensitivity factors. TO construction cost overruns borne by developer in excess of 10% threshold.

FERC Order 2023 §35.28(c)(12)

NUC Cost Trend — By Cluster Generation

2019 — Clusters 8–10

Average NUC ~$50k/MW

Desert solar dominated. Most projects in high-irradiance, low-constraint areas of Mojave and San Joaquin. Network upgrade costs were relatively modest — existing 500kV infrastructure had adequate headroom.

2021 — Clusters 11–12

Average rose to ~$95k/MW

Bay Area, coastal, and offshore-adjacent projects introduced high-voltage upgrade requirements (345kV and 500kV substation work). Storage co-location increased interconnection complexity. First significant TPD-triggered withdrawals.

2023 — Cluster 13 Phase II

Several projects withdrew when NUC exceeded $200k/MW

Cluster 13 resulted in a reassessment after high Phase II NUC allocations — some projects faced costs of $180–250k/MW, exceeding project economics. Triggered mandatory cluster reassessment under CAISO tariff (>15% MW withdrawal rule).

2024 — Cluster 14 Phase I

Pre-assessments indicate $120–180k/MW range

Cluster 14 Phase I results released. Early NUC estimates for Cluster 14 suggest $120–180k/MW average, driven by Bay Area and coastal projects. Solar+storage co-located projects trending cheaper per MW than standalone offshore.

2025 — First Offshore Wind Studies

Expected $250–400k/MW range for floating OSW

CAISO initiating first interconnection feasibility studies for Humboldt Bay floating offshore wind. No HVDC path currently exists — new transmission infrastructure required. Cost estimates based on BOEM EA modeling and European analogues.

2026 — FERC Cost Cap Reform

CAISO proposed cost cap reforms under RM22-14

CAISO supporting FERC rulemaking on NUC cost caps for cluster studies. Proposed $5M base cap with overflow mechanism. Aim: reduce uncertainty-driven withdrawals that trigger reassessments and delay viable projects.