JEPX Spot Market Trading Data

What you can build

• Schedule a battery on tomorrow's area price

  Read the 48 area prices for your region from the current spot_summary file once the next delivery day appears. The operator proposes charge slots at the lowest prices and discharge slots at the highest, for your approval.

  With Battery Dispatch

• Move a deferrable process out of the peak slots

  Compare the DA-PT (13:00-16:00) and DA-DT (8:00-22:00) index values with your area's 30-minute prices. The operator proposes shifting a deferrable run into the cheaper slots and records the prices it compared.

  With Price Shift

• Pre-cool ahead of an expensive afternoon

  When tomorrow's area price curve peaks in the afternoon slots, the operator proposes an overnight or morning pre-cool schedule for the building and names the slots that triggered it.

  With Peak Demand

Requirements

• A POST to /_download.php with dir=spot_summary (or spot_index) and file=spot_summary_<year>.csv, as the page's download form sends
• A Shift_JIS decoder and a mapping from the Japanese column headers
• The fiscal-year convention: each file starts on 1 April
• Source attribution to JEPX on any reuse

Authentication

No key. The CSV files are served in reply to a form post on the public site; no account is documented.

Limits

• No API: data comes as yearly CSV files behind a download form, with Japanese column headers in Shift_JIS encoding
• One file per fiscal year from April; the current file grows by 48 rows per delivery day, so a client re-reads it
• JEPX gives no guarantee of accuracy or completeness and may change or delete posted information without notice
• Detailed trading rules are in the Japanese trading guidelines; the English outline covers only the product and the auction form

Questions and answers

Is there an API for JEPX spot data?

No. The market data page renders from CSV files. Its Data Download form posts dir=spot_summary and a file name such as spot_summary_2026.csv to /_download.php, which returned the file as application/octet-stream. The page's year list ran from 2005 to 2026 when fetched.

What columns does spot_summary hold?

Delivery date, time code (1 to 48), sell bid volume, buy bid volume and contracted total volume in kWh, the system price, area prices for the nine areas in JPY/kWh, and sell and buy block bid totals with their contracted totals. Headers are in Japanese and the file is Shift_JIS.

When does the next day's price appear?

The Spot Market trades electricity for delivery the next day in a blind single price auction. The current fiscal-year file fetched on 20 September 2026 already held all 48 products for 21 September. JEPX's English pages state no publication time.