gridvitals
Obs. — (—)

Tokyo area power supply & demand

May 27, 2026 (Wed)10:33 JST
地図を読み込み中…
Stable

Recommended actions

No special conservation action needed at this time.

  • 1Use electricity as normal
  • 2Continue everyday energy-saving habits (LED lights, efficient appliances)

Data sources

Provider: —

Refresh: clients poll every 60 s; Edge layer caches for 60 s. Observation time uses the timestamp embedded in the CSV.

Inter-regional interconnection & power flow

Arrow: estimated flow from areas with greater reserve toward tighter areas (based on reserve-margin differences)

900MW6,190MW2,100MW300MW2,500MW1,900MW4,140MW1,400MW1,200MW2,780MWHokkaido—Reserve —Tohoku—Reserve —Tokyo—Reserve —Chubu—Reserve —Hokuriku—Reserve —Kansai—Reserve —Chugoku—Reserve —Shikoku—Reserve —Kyushu—Reserve —Okinawa—Reserve —
How to read: each area's reserve margin = (Supply − Demand) / Supply. The map shows the likely direction of power flow over interconnection lines, from areas with more reserve to those with less. Arrow thickness scales with the reserve-margin difference.
All areas have reserve margins above 8% — flow capacity is comfortable.

Frequently asked questions

Q&A on power supply/demand, conservation, blackout preparation, and data sources

Q. Where do you get the power supply/demand data?
From the public 'denki-yoho' CSV files published by each of Japan's 10 transmission/distribution utilities (Hokkaido EPN, Tohoku EPN, TEPCO PG, Chubu Electric PG, Hokuriku T&D, Kansai T&D, Chugoku EPN, Yonden T&D, Kyuden T&D, Okinawa Electric). They are fetched via an Edge Function, decoded from Shift_JIS to UTF-8, and parsed.
Q. How real-time is the data?
Each utility updates its CSV every 5 minutes (Kyushu every 60 minutes). gridvitals caches at the Vercel Edge layer for 60 seconds and the client polls every 60 seconds, so effective freshness is about 6 minutes.
Q. What are the grid-stress thresholds?
Based on the Agency for Natural Resources and Energy's 'power supply/demand stress advisory and warning' framework: usage rate ≥ 92% = busy, ≥ 95% = stress advisory, ≥ 97% = warning level.
Q. What should I do when the grid is stressed?
Ease A/C set points by 1–2 °C (cooling 28 °C / heating 20 °C are good targets), unplug unused lights and appliances, shift laundry, cooking, and other heavy loads outside the 17:00–20:00 peak, and prepare a flashlight and power bank in case of an outage.
Q. How do I prepare for a wide-area blackout?
Keep a flashlight, power bank, drinking water, and some cash on hand. Boost the fridge's cold mass with frozen water bottles. Avoid elevators — use stairs. Agree on a family meeting place. Always prioritize health and safety.
Q. How do utilities share power across regions?
Japan's regional grids are linked by 'inter-regional interconnection lines.' Power can be sent from areas with reserve to areas in deficit. Examples include the Hokkaido–Honshu HVDC link, the frequency converters between eastern (50 Hz) and western (60 Hz) Japan, and the Kanmon line between Chugoku and Kyushu. gridvitals estimates likely flow direction from each area's reserve margin and visualizes it.
Q. What's the source of the weather data?
The free Open-Meteo API. When you grant location access we use your coordinates; otherwise we use the centroid of the selected area. We display current temperature, humidity, wind speed, an 8-hour hourly forecast, and 3-day highs/lows with precipitation probability.
Q. Is this an official site?
No. gridvitals is an unofficial visualization that re-broadcasts publicly published data. For authoritative supply-and-demand information or conservation requests, always refer to each utility's official announcements.

About gridvitals

gridvitals is a free dashboard that visualizes Japan's electricity supply and demand in real time. It fetches the 'denki-yoho' CSVs published every few minutes by each of Japan's 10 transmission/distribution utilities (Hokkaido, Tohoku, Tokyo, Chubu, Hokuriku, Kansai, Chugoku, Shikoku, Kyushu, Okinawa) and aggregates per-area usage rate, forecast demand, supply capacity, and reserve margin into a single screen.

Your area is detected automatically from your browser location and shown alongside the local weather, temperature, and precipitation probability. During heating/cooling peaks (mid-summer and mid-winter) this lets you grasp at a glance how tight power is in your region right now. When usage climbs, gridvitals shows a four-stage action guide (stable / busy / tight / critical) and basic blackout preparation tips (flashlight, power bank, boosting fridge cold mass, etc.).

gridvitals also visualizes the direction and capacity of power transfers over inter-regional interconnection lines, so you can see which neighboring area might supply power to yours when local supply is insufficient. This helps make sense of wide-area outage events such as the 2018 Hokkaido Eastern Iburi earthquake blackout.

This is an unofficial tool. For official grid-stress warnings and conservation requests, please refer to the Agency for Natural Resources and Energy, OCCTO, and the individual transmission/distribution utilities.