JEPX Five Bidding Methods Explained: Normal, Block, Linked Block, Exclusive Block & Stripe Bids

Introduction: Why Multiple Bidding Methods?

The JEPX spot market (day-ahead market) trades electricity for the following day across 48 time slots of 30 minutes each. Electricity generation has physical constraints — generators have minimum output requirements, startup and shutdown costs are significant, and some units must operate in coordination. A simple "each slot bids independently" approach cannot meet the needs of all market participants. To address this, JEPX has designed five bidding methods, enabling different types of generators and retailers to participate in the market in ways that align with their operational logic.

1. Normal Bid

The Normal Bid is the most fundamental bidding method, available to all market participants. Each 30-minute slot is bid independently, and the clearing outcome of each slot does not affect any other slot.

1.1 Bid Specifications

Item	Specification
Slot Range	Single 30-minute slot
Bid Unit	0.1 MW (100 kW)
Price Range	¥0.01 – ¥200/kWh
Max Bid Orders per Slot	60 sell orders, 60 buy orders
Clearing Method	Per-slot independent, blind single-price auction

1.2 Use Cases

Normal Bids are suited for flexible resources such as hydropower, batteries, and demand response (DR) assets, as well as retailers who wish to selectively sell power in specific high-price slots. Since each slot clears independently, bidders can set different price strategies for different slots, fully exploiting intraday price differentials.

2. Block Bid

A Block Bid allows bidders to bundle consecutive slots into a single "block" with a unified bid price. The clearing condition is all slots clear simultaneously, or none clear at all (All-or-Nothing).

2.1 Bid Specifications

Item	Specification
Slot Range	2 to 48 consecutive slots
Bid Price	Unified (weighted average concept)
Clearing Condition	Weighted average market price across all block slots ≥ bid price (sell side)
Clearing Method	All contracted or all not contracted
Max Blocks per Day	20 sell blocks, 20 buy blocks

2.2 Use Cases

Block Bids are primarily used to guarantee the minimum output (Minimum Output) requirements of thermal power units. Once a thermal unit starts, it must maintain a minimum output level for a certain period to be economically viable. If only some slots clear, the unit may be forced to operate under uneconomic conditions. Block Bids ensure that the unit either sells power across the entire planned operating period or stays out of the market entirely, protecting the unit's economic viability.

3. Linked Block Bid

The Linked Block Bid is an advanced form of the Block Bid, allowing bidders to establish a linkage between a "Master Block" and one or more "Slave Blocks." The clearing rule is: when the Master Block clears, the Slave Block(s) may also clear simultaneously; when the Master Block does not clear, the Slave Block(s) are also forced not to clear.

3.1 Bid Specifications

Item	Specification
Structure	1 Master Block + 1 or more Slave Blocks
Slot Range	Master and slave each cover consecutive slots (non-overlapping)
Clearing Condition	Master clears → Slave may clear; Master does not clear → Slave must not clear
Slave Independent Clearing	Not permitted (must depend on Master)

3.2 Use Cases

Linked Block Bids are suited for master-slave unit combined operation scenarios. For example, when a large thermal power plant (master unit) starts up, its waste heat can be used by a cogeneration facility (slave unit); if the master unit fails to clear the market, the slave unit cannot operate independently. Through Linked Block Bids, the output of both units can be managed as a whole in the market, avoiding operational difficulties caused by partial clearing.

4. Exclusive Block Bid

The Exclusive Block Bid allows bidders to set two groups of blocks, requiring both groups to clear simultaneously, or both groups to be rejected simultaneously. Unlike Linked Block Bids, the two groups in an Exclusive Block Bid are equal in status — there is no master-slave distinction.

4.1 Bid Specifications

Item	Specification
Structure	Two equal groups (Group A + Group B)
Slot Range	Each group covers consecutive slots (non-overlapping)
Clearing Condition	Both groups' weighted average market prices meet threshold → both clear; either group fails → both rejected
Single Group Independent Clearing	Not permitted

4.2 Use Cases

Exclusive Block Bids are suited for scenarios where two generating units must operate in coordination, such as the gas turbine and steam turbine in a Gas Turbine Combined Cycle (GTCC) plant, or two hydropower units that require coordinated dispatch. When the output of two units can only achieve optimal economic benefit by entering the market simultaneously, the Exclusive Block Bid ensures the market either accepts the entire combination or rejects it completely, avoiding the inefficiency of isolated single-unit operation.

5. Stripe Bid

The Stripe Bid is a special bidding method that mandatorily covers all 48 time slots. Each slot can have a different bid price, but slots still clear independently. The core purpose of Stripe Bids is to fulfill the Same-Value Obligation — Japanese retail electricity suppliers are legally required to submit buy bids for all 48 slots in the JEPX spot market for the following day.

5.1 Bid Specifications

Item	Specification
Slot Range	Mandatory coverage of all 48 slots
Per-Slot Price	Individually configurable (no need to be uniform)
Clearing Method	Per-slot independent (same as Normal Bid)
Primary Obligation	Retail supplier same-value obligation compliance
Bid Direction	Buy bids (retailers) or sell bids

5.2 Same-Value Obligation Explained

Under Japan's electricity system reform regulations, retail electricity suppliers holding supply contracts are obligated to submit buy bids equal to their forecast demand quantity for all 48 slots in the JEPX spot market for the following day (Same-Value Obligation). Stripe Bids are designed precisely for this purpose — suppliers can complete bids for all 48 slots at once, setting different bid prices for each slot based on forecast market prices, balancing compliance obligations with bidding efficiency.

6. Comparison of Five Bidding Methods

Bidding Method	Slot Range	Clearing Method	Primary Use	Typical Users
Normal Bid	Single slot	Per-slot independent	General electricity trading	All participants
Block Bid	Consecutive slots	All-or-nothing	Minimum output guarantee	Thermal/nuclear generators
Linked Block	Consecutive slots (master-slave)	Master clears or both clear	Master-slave combined operation	Cogeneration, combined units
Exclusive Block	Consecutive slots (two groups)	Both clear or neither clears	Linked unit combinations	GTCC, coordinated hydro units
Stripe Bid	All 48 slots	Per-slot independent	Same-value obligation compliance	Retail electricity suppliers

7. Practical Bidding Strategy Recommendations

Combining multiple bidding methods: In practice, a single market participant often uses multiple bidding methods simultaneously. For example, a power company with both thermal units and batteries might use Block Bids to guarantee minimum output for the thermal units, Normal Bids for flexible arbitrage with the batteries, and Stripe Bids to fulfill the same-value obligation on the retail side.

Weighted average calculation for Block Bids: Before submitting a Block Bid, carefully calculate the weighted average of expected market clearing prices across all slots in the block to confirm the bid price is reasonable. When market prices are highly volatile, consider shortening the block duration or splitting into multiple shorter blocks to reduce the risk of full rejection.

Price setting for Stripe Bids: When setting Stripe Bid prices, retailers typically add a premium above the forecast market clearing price to ensure clearing in most slots, thereby completing the same-value obligation. However, care must be taken to avoid clearing at excessively high prices in low-price slots, which would unnecessarily increase procurement costs.

For a detailed explanation of the JEPX market system — including types of market participants, clearing mechanisms, and compliance obligations — please refer to Article 21: JEPX Trading System Complete Guide.