Japan Capacity Market Complete Guide: Auction Mechanism, Provider Qualifications, and Capacity Fee Calculation

1. What Is the Capacity Market?

Japan's capacity market (容量メカニズム) is a cornerstone of the country's electricity system reform, launched formally in 2020 and operated by the Organization for Cross-regional Coordination of Transmission Operators (OCCTO). Its core purpose is to ensure that Japan's electricity system maintains sufficient generation capacity (kW) over the coming years to meet demand peaks and sustain supply reliability.

2. Capacity Market vs. Energy Market: A Fundamental Distinction

Dimension	Energy Market (JEPX Spot)	Capacity Market
Traded commodity	Energy (kWh)	Capacity (kW)
Trading timing	Day-ahead, per 30-minute slot	4 years ahead, annual auction
Settlement basis	Actual generation volume	Committed capacity (kW)
Primary purpose	Short-term supply-demand balance	Long-term capacity adequacy
Operating body	JEPX	OCCTO

In essence, the energy market answers "how much electricity is needed right now," while the capacity market answers "will there be enough power plants in the years ahead."

3. The Capacity Auction Mechanism

The capacity market uses a Main Auction held annually, procuring capacity for a delivery year four years in the future. For example, the auction conducted in 2024 procures capacity for fiscal year 2028 (April 2028 – March 2029).

3.1 Auction Process

The auction employs a Uniform Clearing Price mechanism: all successful bidders receive the same clearing price (JPY/kW/year) regardless of their individual bid prices.

1. Demand curve setting: OCCTO calculates the required total capacity based on reliability standards (target reserve margin) and sets a downward-sloping demand curve.
2. Capacity provider bidding: Qualified providers submit bids specifying available capacity (kW) and minimum acceptable price (JPY/kW/year).
3. Clearing calculation: OCCTO ranks all bids from lowest to highest price; the intersection with the demand curve determines the clearing price and procured volume.
4. Capacity contract execution: Successful bidders sign 4-year capacity contracts with OCCTO, committing to deliver the specified capacity during the delivery year.

3.2 Historical Auction Results (Rounds 1–6)

Japan's capacity market has conducted six main auctions from 2020 to 2025. The pricing mechanism has evolved from a single national clearing price to a multi-area segmented pricing system.

Round	Auction Year	Delivery Year	Procured Capacity (万kW)	Clearing Price Summary (JPY/kW/year)
Round 1	2020	FY2024	16,769	14,137 (national single price)
Round 2	2021	FY2025	16,534	3,495 (national single price)
Round 3	2022	FY2026	16,271	Hokkaido 8,749 / Tohoku–Tokyo 5,833–5,834 / Chubu and west 5,832 / Kyushu 8,748
Round 4	2023	FY2027	16,745	Hokkaido 13,287 / Tohoku 9,044 / Tokyo 9,555 / Chubu–Hokuriku 7,823 / Kansai–Chugoku–Shikoku 7,638 / Kyushu 11,457
Round 5	2024	FY2028	16,621	Hokkaido 14,812 / Tohoku–Tokyo 10,280 / Chubu–Hokuriku–Kansai–Chugoku–Shikoku 8,785 / Kyushu 13,177
Round 6	2025	FY2029	16,608	Hokkaido 14,972 / Tohoku–Tokyo 15,111 / Chubu–Hokuriku–Kansai–Chugoku–Shikoku 12,388 / Kyushu 15,112

4. Capacity Provider Qualification Requirements

Resource Type	Capacity Calculation Method	Notes
Thermal (gas, coal, oil)	Nameplate capacity × availability factor	Primary resource, highest share
Nuclear	Nameplate capacity × availability factor	Requires restart approval
Hydro (incl. pumped storage)	Seasonally adjusted capacity	Higher summer capacity; pumped storage requires ≥3 hours generation capability
Solar PV	Nameplate × low contribution factor (3–8%)	Low rating due to output variability
Wind	Nameplate × low contribution factor (5–10%)	Same rationale as solar
Battery storage (BESS)	Discharge power (kW) × evaluation factor	Eligible as Stable Resource from FY2027 auctions (requires ≥3 hours discharge duration)
Demand Response (DR)	Curtailable load (kW) × adjustment factor	Participates as Dispatch-Command Resource; minimum 1,000 kW required
Interconnection capacity	Available transmission capacity (kW)	Managed centrally by OCCTO

4a. BESS Participation Requirements in Detail

4a.1 Resource Classification and Minimum Discharge Duration

BESS classification in the capacity market depends on scale and discharge duration:

Condition	Resource Classification	Applicable Period
Expected capacity ≥1,000 kW AND discharge duration ≥3 hours	Stable Resource (highest evaluation)	Applicable from FY2027 auctions onward
Expected capacity ≥1,000 kW BUT discharge duration <3 hours	Dispatch-Command Resource	All periods
Expected capacity <1,000 kW (standalone)	Dispatch-Command Resource (aggregation required)	All periods

4a.2 BESS Performance Obligations (Stable Resource Registration)

Obligation	Content	Penalty for Non-Compliance
Planned outage coordination	Comply with OCCTO capacity outage plan adjustment requests	Non-adjustment days × 0.3% (standard) or 0.6% (supply reliability impact) × contract value
Market bidding	Bid remaining capacity into wholesale electricity markets	Reduction based on violation severity
Supply instruction response	Receive TSO supply instructions; provide remaining capacity after gate closure	Shortfall × contract value / annual low-reserve hours (~30 hours)
Capability verification test	Annual effectiveness test confirming supply capacity ≥ contracted capacity	Capacity below contracted level after test triggers market exit for that portion
No decommissioning or output reduction	Cannot decommission or reduce output beyond necessary levels during delivery year	Reduction based on violation severity

4b. DR (Demand Response) Participation Requirements in Detail

4b.1 DR Resource Classification

DR resources participate in the capacity market as "Dispatch-Command Resources" — an aggregated resource type that allows aggregators to bundle multiple small-scale DR assets for market participation.

Requirement	Content
Minimum scale	Expected capacity ≥1,000 kW per metering unit (achievable through aggregator bundling)
Participant eligibility	Generation business operators, DR aggregators, or delegation to retail electricity suppliers
Metering equipment	Installation of verifiable metering devices (smart meters, etc.) to confirm demand reduction volumes
Simple command system	OCCTO online command system must be built by end of February, three years before the delivery year
Expected capacity calculation	Calculated by multiplying historical demand reduction performance by an adjustment factor

4b.2 DR Performance Obligations (Dispatch-Command Resource)

Obligation	Content	Penalty for Non-Compliance
Dispatch command response	Receive dispatch commands; provide supply capacity ≥ contracted capacity for up to 12 dispatches/year × 3 consecutive hours each	Shortfall × contract unit price × 110% × (shortfall / contracted capacity × 12 dispatches × 3 hours)
Effectiveness test	Annual (summer and winter) OCCTO effectiveness tests confirming supply capacity ≥ contracted capacity	Capacity below contracted level after test triggers market exit for that portion
Supply provision method	Demand reduction achieved through bilateral contracts with retail suppliers or bidding into wholesale electricity markets	—

Note: The TSO may issue more than 12 dispatch commands per year (excess dispatches are not counted in penalty calculations), but DR operators should thoroughly assess their resource response reliability before entering into capacity assurance contracts.

5. Capacity Fee Calculation and Cost Pass-Through

5.1 Total Capacity Fee Calculation

Total capacity fee for delivery year = Clearing price (JPY/kW/year) × Procured capacity (kW)

FY2024 example: ¥14,137/kW/year × 167,690,000 kW ≈ ¥2.43 trillion

5.2 Allocation to Retailers

Retail electricity suppliers bear capacity contributions in proportion to their annual peak kW share, while general TSOs bear contributions based on each area's H3 demand forecast:

Each supplier's capacity contribution ≈ Total national capacity fee × (Supplier's annual peak kW share ÷ National total share)

5.3 Capacity Contribution Levy Trend (FY2024–FY2029)

The following shows the national average unit price trend of capacity contributions actually borne by retail electricity suppliers (based on H3 demand forecast values):

Delivery Year	National Average Unit Price (JPY/kW/year)	Corresponding Auction Clearing Price	Notes
FY2024	775	14,137 (Round 1)	First year of the system; high transitional deduction rate
FY2025	248	3,495 (Round 2)	Clearing price plunged; levy at historic low
FY2026	409	5,832 (Round 3 avg.)	First market segmentation; price recovery
FY2027	622	~9,500 (Round 4 avg.)	Continued increase; capacity tightness signal
FY2028	879	~10,000 (Round 5 avg.)	High-price segmentation in Hokkaido and Kyushu
FY2029	~1,200+ (estimated)	13,303 (Round 6 avg.)	Record-high clearing price; final year of transitional deduction (5.1%)

5.4 Reflection in End-User Bills

Retail suppliers incorporate capacity contributions as a cost component in end-user electricity tariffs, typically labeled as "capacity fee" or "system maintenance fee," charged based on the customer's contracted demand (kW) or consumption (kWh).

6. Strategic Implications for Retail Electricity Suppliers

6.1 Capacity Contributions Are a Fixed Cost

Unlike JEPX spot prices, capacity contributions are a fixed cost tied to supply volume that cannot be avoided through market operations. For PPS, accurately forecasting future supply volume is the key to managing capacity contribution costs.

6.2 Dual Participation Opportunity

PPS with their own generation assets can simultaneously participate as capacity providers, using capacity fee income to offset their capacity contribution payments — or even generate net revenue. This "dual participation" strategy is a significant competitive advantage for large integrated electricity suppliers.

6.3 DR Resources as Capacity Market Assets

VPP aggregators and industrial DR resources can participate in the capacity market as "demand response capacity." For pure retailers without generation assets, developing DR resources and entering the capacity market is an important pathway to reducing net capacity contribution costs.

7. Controversies and Reform Directions

7.1 The Low Contribution Factor Problem for Renewables

Solar and wind capacity contribution factors of only 3–10% are far below their nameplate capacity. Critics argue this design undervalues renewable contributions and hinders the energy transition. Proponents counter that without large-scale storage, variable renewables cannot reliably provide "firm capacity" during peak demand periods.

7.2 The "Life Extension" Effect for Aging Thermal Plants

Capacity fees provide financial incentives for aging thermal plants to remain operational, which some environmental groups criticize as an obstacle to carbon neutrality. METI is studying a differentiated mechanism that would prioritize "decarbonized capacity."

7.3 2026 Reform Priorities

Based on Japan's 7th Strategic Energy Plan, capacity market reforms include: enhanced capacity recognition for hydrogen and ammonia fuel plants; higher capacity contribution factors for battery storage systems; and research into introducing long-term Contracts for Difference (CfD) to provide more stable investment returns for new low-carbon generation.

"The capacity market is Japan's last line of defense for power system reliability. Understanding its mechanics is a prerequisite for evaluating the long-term investment value of Japan's electricity market."