How much battery capacity is actually coming?

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172 GW enters the funnel and 640 MW comes out. Only 0.4% is connected, and applications exceed the state's 2040 outlook threefold.

To connect a battery to the grid you first apply for a connection study, receive the utility's response, apply for a contract, pay the construction charge and wait for the works. Here is the mouth and the neck of that funnel, in the Agency for Natural Resources and Energy's figures.

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Fig. 1 — The mouth is wide, the neck is narrow. Against 172 GW wanting to connect, 640 MW is actually connected (end-December 2025). Source: Agency for Natural Resources and Energy, 9th Next-Generation Power Grid WG (27 March 2026).

The mouth doubled in 15 months; the neck quadrupled in 12

Connection studies in process rose from about 88 GW at end-September 2024 to about 172 GW at end-December 2025 — a doubling in roughly fifteen months. Contract applications in process rose from about 6.2 GW to about 30 GW over the same period, close to fivefold (the state's official indicator gives about 24 GW, roughly 3.9×, from end-September 2024 to end-September 2025). Volume actually connected, meanwhile, rose from about 170 MW at end-December 2024 to about 640 MW at end-December 2025 — roughly fourfold in a year, but two orders of magnitude below the mouth.

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Fig. 2 — Applications pile up; connections grow slowly. Sources: Agency for Natural Resources and Energy materials, various meetings (end-September 2024 to end-December 2025).

Why the neck is narrow

Three reasons. Per operator interviews conducted by the Agency for Natural Resources and Energy: some projects face a three-to-five-year wait on grid-side works even after paying the construction charge and starting on site; lead times for receiving and transforming equipment have stretched; and the application pile contained many projects holding a seat with neither land nor funding behind them. The state introduced remedies in 2026 — raising the deposit on contract applications (April), capping the number of connection studies per company (1 August), and a planned amendment requiring documentary proof of land rights with a contract application (due October). The direction is to reduce seat-blocking.

The state has no target

Foreign investors ask how many GW of batteries Japan intends to install. The answer is that there is no target, but there is an outlook. At a March 2026 advisory council, the Agency for Natural Resources and Energy put its FY2040 outlook for supply-side batteries (grid-scale and renewables-co-located) at 2.8–10 GW, with current installed volume at 500 MW (the scope and reference date differ from the 640 MW connected figure). At the same meeting the state itself explained that contract applications, at 24 GW as of end-September 2025, already exceed the range of the outlook. So contract applications stand at three times the upper end of the state's 2040 outlook, while the 640 MW connected is about a quarter of its lower end. Abroad it is different. The United States connected 15 GW of new batteries in 2025 and plans 24 GW in 2026 (EIA). Texas alone has 178 GW of battery connection applications (ERCOT, February 2026) — the same order of magnitude as Japan's 172 GW of connection studies. Australia's system operator AEMO writes in its plan that 49 GW / 646 GWh of storage (including pumped and demand-side) is needed by 2050 (48-18).

How an investor should read this

A narrow neck means few storage plants actually connected. Projects with a confirmed connection date, and projects already running, should be counted separately from the mountain of applications. The state has moved to reduce seat-blocking; the effect is still to come. There is no national target, and the real ceiling is set by the grid's receiving capacity and the order of the works queue.

The questions in this series

I. Why the grid ran without batteries in the past

II. Why thermal, nuclear and pumped storage are not enough

III. Where demand and the generation mix are heading

48-10Why do data centres point to batteries?
48-11What happens to solar from here?
48-12Thermal volume, nuclear operation, demand — what next?
48-13How much battery capacity is actually coming? (this article)

IV. The money, and what the state really wants

The one question beyond the 1848-20 What do you pay, and what comes back?The answer differs by project, so we have built a calculator whose dials are made only from published figures. You can move unit price, clearing rate, seat fee, arbitrage spread and construction cost yourself.

Sources

Agency for Natural Resources and Energy, 9th Next-Generation Power Grid WG, 27 March 2026, materials and minutes (end-December 2025: approx. 640 MW connected, approx. 30 GW contract applications, approx. 172 GW connection studies)
Agency for Natural Resources and Energy, 1st Next-Generation Power Grid WG, Material 3, 23 January 2025 (end-September 2024: connection studies approx. 88 GW, connection contracts approx. 6.2 GW); 2nd meeting, Material 2, 17 March 2025 (end-December 2024: approx. 170 MW connected); 7th meeting, Material 1-1, 9 February 2026 (end-September 2025: contract applications approx. 24 GW, approx. 3.9× year on year; operator interviews)
Agency for Natural Resources and Energy, 10th Next-Generation Power Grid WG, Material 2, 16 April 2026 (cap on the number of connection studies, in force 1 August 2026); 11th meeting, Material 2, 10 June 2026 (documentary requirement for land rights, due October 2026)
Agency for Natural Resources and Energy, 2nd Distributed Energy Promotion Strategy WG, minutes and Material 5, 6 March 2026 (supply-side resources: 500 MW currently, FY2040 outlook 2.8–10 GW, contract applications of 24 GW exceeding the outlook)
ERCOT, "Large Load Update," 9 April 2026 (energy storage among generation interconnection applications: 177,642 MW, as of February 2026)
U.S. EIA, "Today in Energy," 20 February 2026 (15 GW added in 2025; 24 GW planned for 2026)
AEMO, 2024 Integrated System Plan (49 GW / 646 GWh by 2050)

Supervised by

Shinya Nakashima(Representative Director, Science X Inc.; Ph.D. in Engineering)

Works on the development, sale and technical due diligence of grid-scale battery storage plants. This column is written and supervised on the basis of hands-on transaction and evaluation practice.