- Whether ★1 is needed depends on the day the grid operator accepted the contract application. It is 1 April 2027 for extra-high and high voltage, and 1 October for low voltage.
- The requirement does not apply retroactively to existing plants. If you add a battery to an existing solar plant, ★1 is needed only for the added devices.
- When you replace a device, the new device generally needs ★1. Only in cases of "excessive burden", such as having to replace other devices too, can you submit a plan and get a grace period.
"Our solar plant was connected in 2019. If we add a battery next to it, do we have to replace the solar PCS too?" This is the first question that comes up when a battery is added to an existing solar plant.
In June 2026, when we wrote COLUMN 14, the materials did not say how this was treated. In July, ANRE answered in its FAQ. In October, the draft revision put it into the text. This article sets the line out in one diagram and one table.
The starting point is the acceptance date of the contract application
Whether ★1 is needed depends on the day the grid operator accepted the contract application. It applies to projects accepted on or after 1 April 2027 for extra-high and high voltage, and on or after 1 October 2027 for low voltage.
"Acceptance" is the point when the application documents are complete and the deposit has been paid. It is not enough to have applied for a connection study or received its reply.
Merely having a connection study application accepted does not secure the previous treatment. The previous treatment applies only if you file a contract application on the basis of the study result and the grid operator has accepted that contract application.ANRE, "Frequently asked questions", A2 (our translation)
If your project has "filed the contract application, but the deposit is still to come", the acceptance date could fall after April 2027. Check the date first.
Terms used in this series
This series uses the terms below. All four articles share the same table.
| Term | Meaning |
|---|---|
| JC-STAR | A security labelling scheme for devices connected to the internet (IoT devices). METI launched it in March 2025. The Information-technology Promotion Agency, Japan (IPA) runs it. |
| ★1 (Level 1) | The lowest level. The maker checks the basic rules itself and applies. The rules include no default passwords, a contact point for faults, and software that can be fixed. Third-party assessment applies only at ★3 and ★4. |
| PCS (power conditioning system) | The machine that changes the form of electricity between the battery (DC) and the grid (AC). It is the heart of a storage site. |
| BMS | The battery management system. It watches the temperature and voltage of the battery. |
| EMS | The energy management system. It decides when to charge and when to discharge. |
| Remote monitoring / gateway | The front door that connects a power plant or storage site to outside networks. |
| The grid / grid connection | The grid means the transmission and distribution lines of the power companies. Connecting a power plant or storage site to it is called grid connection. |
| Grid operator (general transmission and distribution operator) | The transmission and distribution companies of the large power utilities. There are 10 across Japan, such as Tokyo Electric Power Grid. |
| Connection study | A procedure in which the grid operator checks whether a site can connect and how much the works will cost. It comes before the contract application. |
| Contract application | The formal application filed after the connection study reply. It counts as accepted only when the documents are complete and the deposit has been paid. |
| Extra-high voltage, high voltage, low voltage | The voltage classes of the connection. High voltage is roughly under 2,000 kW and low voltage is under 50 kW. Extra-high voltage is larger than both. |
The diagram
Figure 1 shows the flow of which devices in which projects need ★1. Follow it from the top.
No retroactive application
The draft says the requirement is "not applied retroactively" to projects whose acceptance is complete. This holds even if the equipment has not yet been built.
Even if the equipment has not yet been installed, this requirement shall not apply retroactively to a project for which acceptance of the contract application for the power generation equipment is complete.Guideline on Technical Requirements for Grid Interconnection, draft revision, Chapter 2, Section 1, 5 (1) (October 2026) (our translation)
A solar plant connected in 2019 is unaffected as long as it is used as it is.
But even for a project whose acceptance is complete, replacing the PCS or other devices with different ones after April 2027 requires an application for a change to the equipment. The requirement at that time then applies, so the replaced devices need ★1 (FAQ A3).
If you add, only the added side
When you add a battery to an existing solar plant, ★1 is needed for the devices on the added battery side. These are the PCS, BMS, EMS, remote monitoring unit, gateway and so on. The existing solar PCS and monitoring unit need nothing if they are not replaced.
For the covered devices used in an added battery, please use JC-STAR ★1 certified products.ANRE, "Frequently asked questions", A10 (our translation)
Switching from FIT to FIP and the end of the FIT period are not covered either, as long as no equipment is added or changed. If you add a battery at the same time as switching to FIP, only the added battery needs ★1. Even a fully self-consumed plant, which sends no power out, is covered if it is connected to the grid.
The devices covered change with the way the system is connected. Table 1 lists, for each configuration, the devices that need ★1 and the basis. The two DC-coupled rows are not described directly in the materials. They are our reading.
| Configuration | Devices that need ★1 | Basis |
|---|---|---|
| A new build | All control devices connected to the internet (PCS, BMS, EMS, remote monitoring, gateway and so on) | Draft 5 (1) |
| Adding a battery to an existing solar plant (AC-coupled; the current PCS stays) | PCS, BMS, EMS and gateway on the added battery side | FAQ A10 |
| Adding a battery to an existing solar plant (DC-coupled; the PCS is replaced with a type that can also serve the battery) | The replaced PCS, and the devices on the added battery side | "Replacement" in draft 5 (2). Our reading |
| Adding a battery to an existing solar plant (DC-coupled; the current PCS stays, and a battery and BMS are added on the DC side) | The devices on the added battery side | Our reading |
| Replacing a device, for example after a failure | The replaced device (in principle). Devices that are not replaced are not covered | Draft 5 (2), FAQ A11 |
| Switching from FIT to FIP, or the end of the FIT period (no change to equipment) | Not needed | FAQ |
| Adding a battery at the same time as switching to FIP or the end of the FIT period | Only the added battery side | FAQ A12 |
| Fully self-consumed (no export) | Same as the others if connected to the grid | FAQ A13 |
The treatment of DC-coupled systems is not described directly in the materials. Before you rely on it, confirm it in writing with the local grid operator.
A replaced device generally needs ★1
When you replace one PCS after a failure, that one is in principle required to have ★1. Devices you do not replace are not covered.
If, from April 2027, you replace a covered device with a device that has IP communication, the replaced device is required to be a JC-STAR ★1 certified product.ANRE, "Frequently asked questions", A11 (our translation)
Even a replacement with the same type requires a connection study application under Article 79, paragraph 1, item 2 of the Transmission and Distribution Business Guidelines. It does not count as a "minor change".
The only exception is "excessive burden". ANRE gives three examples.
- Replacing one failed PCS would not match the old PCS or transformer, so the whole equipment would have to be replaced.
- An extended warranty signed by the end of March 2026 does not allow replacement with a ★1 product.
- You bought and hold a replacement product by the end of March 2026, and cannot swap it for a ★1 product.
In such a case, you consult the local grid operator and submit a plan with three points. If it is accepted, you may for now replace the device with a product of the same type without ★1.
- Why you cannot replace it with a ★1 product (with supporting documents)
- When all covered devices will be ★1 (for example, the planned year of replacement)
- The cybersecurity measures until then
At a seminar in April 2026, it was explained that replacing even one device might require all the devices at the plant to be ★1 (as reported by Orrick). The FAQ of July narrowed this to the "replaced device". If you replace 1 of 30 units, only that 1 is covered.
Low voltage is October because of stock in distribution
Only low voltage is six months later, because old products remain in stock in distribution.
Even after makers introduce products with JC-STAR ★1, a certain amount of stock of old products is expected to remain in the distribution network for some time. We therefore set October 2027 as the start date.OCCTO, 21st Grid Code Review Committee, Material 4 (31 March 2026), p. 3 (our translation)
The Japan Photovoltaic Energy Association (JPEA) asked for a grace period until October also for high voltage and other systems that use the same PCS as low voltage. Material for the 22nd Committee (21 August 2026) says that after discussion it was decided "to proceed as proposed". The grace period was not widened.
Schemes that already require ★1
The grid connection requirement starts in April 2027. The auction and the national subsidy already require ★1. Table 2 shows these two schemes and what each asks for.
| Scheme | From when | What it asks for |
|---|---|---|
| Long-Term Decarbonisation Power Source Auction (FY2025 round) | At the bidding procedure | State the model number and JC-STAR registration number for the battery's EMS, PCS and so on (bidding guidelines, 3 September 2025) |
| National subsidy (Grid-Scale Storage System Deployment Support Programme, FY2025 supplementary budget) | At application (call open 4 September to 4 November 2026) | ★1 for BMS, PCS, EMS and so on. A device not covered by ★1 must obtain ★2 before supply starts, if a ★2 standard is later set and covers it |
What to check before you buy
- When the acceptance date of the contract application falls (documents complete plus deposit paid).
- For a project added to an existing solar plant, whether it is AC-coupled or DC-coupled. If DC-coupled, whether the PCS is replaced.
- Whether the model numbers of the devices to be added or replaced are on IPA's list (52-2 The list).
- If you plan to use the excessive burden exception, whether you can assemble the extended warranty contract signed by the end of March 2026, or the papers for a replacement product you hold.
How to read this series
Frequently asked questions
If I add a battery to an existing solar plant, does the solar PCS also need JC-STAR ★1?
No. ANRE's FAQ asks for ★1 in the devices used for an added battery. It does not ask for existing equipment to be replaced with ★1 devices if it is used as it is. ★1 is needed for the PCS, BMS, EMS, remote monitoring and gateway of the added battery side.
If I apply for the connection study by March 2027, do I avoid ★1?
No. The starting point is the day the grid operator accepted the "contract application". That means the point when the documents are complete and the deposit has been paid. Applying for or receiving the reply to a connection study does not secure the old treatment. ★1 is needed for acceptances on or after 1 April 2027 for extra-high and high voltage, and on or after 1 October 2027 for low voltage (under 50 kW).
When I replace a failed PCS, must it be a JC-STAR ★1 product?
In principle, yes. If, from April 2027, you replace a device with one that has IP communication, the new device is required to have ★1. Only where this would be an "excessive burden", for example because other devices would have to be replaced too, you may consult the local grid operator. If you submit a plan stating (1) why you cannot replace it and the evidence, (2) when everything will be ★1, and (3) the measures until then, you may for now replace it with a product of the same type without ★1.
Is JC-STAR ★1 needed for switching from FIT to FIP or at the end of the FIT period?
Not if you do not add or change equipment. If you add a battery at the same time as the switch to FIP or the end of the FIT period, the added battery needs ★1, but the unchanged existing devices do not.
Primary sources and related articles
Requirement text and FAQ
- e-Gov public comment, draft revision of the Guideline on Technical Requirements for Grid Interconnection (case no. 620340012, 6 October to 6 November 2026)JA, Chapter 2, Section 1, 5 (1) and (2)
- ANRE, "Frequently asked questions" (PDF)JA, A1 to A3 and A10 to A13｜ANRE, "Cybersecurity measures for distributed power sources" (July 2026, PDF)JA｜ANRE, "Cybersecurity in the power sector"JA (examples of excessive burden, and the fact that replacement with the same device still needs a connection study)
- OCCTO, 21st Grid Code Review Committee, Material 4 (31 March 2026, PDF)JA, p. 3 (why low voltage is October)｜22nd Committee, Material 3 (21 August 2026, PDF)JA (the request on timing was "to proceed as proposed")
Schemes that already require ★1
- OCCTO, Long-Term Decarbonisation Power Source Auction, bidding guidelines (3 September 2025, PDF)JA
- Sustainable open Innovation Initiative (SII), Grid-Scale Storage System Deployment Support Programme, call for applications (FY2025 supplementary budget, September 2026, PDF)JA, p. 15, item 9, notes 12 and 13
Law firm commentary
- Orrick, Herrington & Sutcliffe, Japan Renewables Alert 72 (19 May 2026)JA (ANRE's explanation at the seminar of 24 April 2026)｜Morrison & Foerster (2 September 2026, PDF)JA