Japan Solar Update: No.159 (July 28 ~ Aug 1, 2025)
As of March 2025, grid connection study applications for grid-scale battery storage in Japan reached 113 GW, a tenfold increase from May 2023. Contract applications totaled around 12 GW. In response, policymakers are advancing reforms to streamline grid access and accelerate the integration of storage systems.
<Key points>
- As of the end of March 2025, applications for connection assessment for approx. 113 GW of grid-scale storage batteries had been received nationwide, and about 12 GW having applied for connection contracts. This represents a roughly tenfold increase in connection assessment applications compared to the end of May 2023
- To enable the prompt grid connection of grid-scale storage batteries, the policy is to further examine institutional measures such as strengthening discipline in grid access procedures and rationalizing connection rules
Applications received for connection assessment and connection contracts of grid-scale storage batteries (as of end Mar. 2025)
Connection assessment nationwide: 11.89 GW (as of end May 2023) → 112.85 GW (as of end Mar. 2025)
Connection contracts nationwide: 1.12 GW (as of end May 2023) → 12.06 GW (as of end Mar. 2025)
Toward prompt interconnection of grid-scale storage batteries
- While further expansion of deployment is expected, a key issue is the prolonged time required for grid connection due to a large number of applications for connection assessment and related factors
- In some cases of grid connection, grid reinforcement is required on the forward power flow (charging) side, leading to taking more time to grid connection
| Matters to be considered | Overview of considerations |
| Strengthening discipline in grid access procedures |
and so on |
| Rationalizing connection rules for grid-scale storage batteries |
Consider specific connection rules for grid-scale storage batteries, referring to measures such as non-firm connections, and real-time control being implemented in the Hokkaido area ahead of other areas and so on |
| Promoting initiatives that enable efficient interconnection of both grid-scale storage batteries and general demand |
In parallel with the revision of connection rules, it is necessary to introduce a framework that enables the smooth grid interconnection of both grid-scale storage batteries and general demand by maximizing the use of existing electric grids, taking advantage of the flexibility of grid-scale storage batteries under the current rules and so on |
Figure 3 Status of applications received for connection assessment and connection contracts of grid-scale storage batteries
Source: Materials of the 3rd meeting of the Working Group on the Next-Generation Electric Grid (June 27, 2025), compiled by RTS Corporation