Japan

How the Japanese market works

Three parties matter for a home battery. A general transmission and distribution company (一般送配電事業者, the local grid company) owns the wires and decides how your equipment may connect. A retailer (小売電気事業者) sells you electricity and sets the tariff. Subsidy programmes are run through bodies such as SII (環境共創イニシアチブ) for the national scheme, and by prefectures and cities for local ones.

The grid company needs to know about any inverter-based equipment. The Japan Electrical Manufacturers' Association (JEMA) explains that each power conditioner, including those of storage batteries, goes through a prior grid connection consultation, and that the technical rules are in the grid interconnection code JEAC 9701 (JEMA: grid connection consultation). We could not read JEAC 9701 itself, so we cannot state its detailed limits.

In Japanese a home storage battery is usually called 家庭用蓄電池 (kateiyō chikudenchi) or 蓄電システム. Searching for those terms finds the subsidy and installer pages that are not available in English.

Why home batteries are popular in Japan

Two things push households towards batteries: outages and the end of generous solar buyback rates. For outages, the Agency for Natural Resources and Energy (ANRE) records that the September 2018 Hokkaido earthquake caused a blackout across the whole island, and that after Typhoon Faxai in September 2019 the peak outage reached about 930,000 households in the Kanto region. Chiba prefecture only fell below 10,000 households without power on 21 September, and it took about 280 hours to restore 99% of the peak (ANRE White Paper 2020, section on a sustainable power system). The same chapter lists storage batteries, solar and electric vehicles among the distributed resources that improve resilience.

For buyback rates, the 10-year FIT contracts of the first rooftop systems began to expire in November 2019. ANRE described that as a chance to move towards using your own power, and it notes that retailers must send each household a notice 6 to 4 months before the end of its contract (ANRE: post-FIT materials). See the next section for how that works today.

A battery cannot guarantee supply in every disaster. It stores a limited amount of energy, and many systems only supply selected circuits during an outage. Ask the installer in writing which circuits are backed up, for how long, and whether the battery can recharge from solar while the grid is down.

FIT and using your own solar power

FIT (feed-in tariff) pays a fixed price per kWh for power you export. For residential solar under 10 kW, ANRE's price page shows ¥15 per kWh for systems under the older terms in the first half of FY2025. For the second half of FY2025, it shows a stepped "initial investment support scheme": ¥24 per kWh for years 1 to 4, then ¥8.3 per kWh for years 5 to 10. The contract period is 10 years (ANRE: FIT and FIP prices, April 2026; ANRE: initial investment support scheme). ANRE describes the design as a way to recover the investment faster.

The same price page lists ¥9.9 per kWh for FY2026 and adds a note that the FY2026 prices for rooftop and residential solar also apply in the second half of FY2025, and that the stepped "initial investment support scheme" design is used for them. The page gives no certification-date ranges and we could not reconcile the ¥9.9 figure with the stepped prices, so ask your installer in writing which price applies to your certification date. We did not review FIP (feed-in premium), which is mainly used for larger plants.

After the FIT period ends, you can sell the surplus to a retailer or aggregator, or use it yourself. ANRE's website lists companies that buy post-FIT power (ANRE: post-FIT materials). We did not compare current buyback offers, so check them. The arithmetic of a battery follows from the price gap: every kWh you store at midday and use in the evening replaces a kWh you would buy at the retail price, and that is worth more than a low export price. We explain the method in how a home battery saves money.

The national subsidy for home batteries (DR programme)

The national subsidy is the household storage programme under the supplementary budget for FY2025 (reiwa 7), run by SII. It pays ¥34,500 per kWh of initial effective capacity, limited to 30% of equipment and installation cost. There are add-ons of ¥2,000 per kWh for resilience criteria and ¥1,000 per kWh for waste-law wide-area certification, and the lowest of the calculated amounts is paid, up to ¥600,000 per application (SII: call for applications, household DR battery).

As an illustration of the arithmetic only: a 10 kWh battery with 10 kWh of initial effective capacity, no add-ons and a price at the programme's ceiling gives ¥34,500 per kWh × 10 = ¥345,000, which is lower than 30% of ¥1,250,000, so ¥345,000 would be paid. At ¥34,500 per kWh the ¥600,000 limit is reached at about 17.4 kWh. Your own result depends on your quote and the product, so ask the seller to calculate it.

The main conditions in the SII document are: the product is registered with SII; the battery passes the fire-spread test under JIS C 8715-2 or IEC 62619 by a third party; it complies with JIS C 4414 and shows the label; the control components (BMS, PCS, EMS) hold JC-STAR ★1 cybersecurity certification; equipment plus installation does not exceed the target price of ¥125,000 per kWh excluding tax; and the system is DR-capable. The consumer applies together with the seller, as joint implementer, and needs a DR contract with a registered aggregator, or must join a registered retailer's DR menu, that continues at least until 31 March 2028.

Demand response means the aggregator or retailer can remotely control when your battery charges and discharges, to balance the grid. Read the contract before you sign: ask how often the battery may be controlled, how much capacity you must keep available, what it pays you, and what happens if you move house. We could not confirm typical terms.

The public call runs from 24 March 2026 to 10 December 2026, or until the budget is reached. Registration of new aggregators and retailers ended on 30 October 2026. The document gives a combined budget for three programmes (household, business and IoT) and no separate budget for the household programme, so applications may close earlier. A separate SII programme exists for business batteries over 20 kWh (SII: business DR battery call). It does not apply to homes.

Tokyo: subsidies and the solar requirement

Tokyo's programme for home batteries is run by the Tokyo Metropolitan Environmental Public Corporation (Cool Net Tokyo). For FY2026 it pays ¥100,000 per kWh of capacity for a new battery package (capped at ¥1.2 million per household without DR) and ¥60,000 per kWh for an added battery unit (capped at ¥720,000). A DR add-on of ¥100,000 is paid if you join a DR demonstration, and the DR contract must be signed before you submit the grant application and performance report. Eligible equipment must be on the SII registered product list (for pre-applications from 1 October 2026, the FY2026 list), and solar must be installed already or at the same time, or you must have a qualifying renewable electricity contract (Cool Net Tokyo: FY2026 home battery subsidy).

You can apply even if you do not live in Tokyo, as long as the equipment is installed in a home in Tokyo. Pre-applications opened on 29 May 2026 and grant applications with the performance report on 30 June 2026. The page lists no closing date, and funds are limited, so check Cool Net Tokyo before you apply. Tokyo's February 2026 budget release (Tokyo Metropolitan Government: FY2026 draft budget) announced the programme before it opened. We could not confirm how long the programme will run beyond FY2026.

Tokyo also runs a group-purchase programme for solar panels, batteries and V2H. Equipment makers and installers are chosen by tender, products are fixed per round, and registration is free with no duty to buy. The current round runs 30 July to 30 November 2026, and the next 1 December 2026 to 31 March 2027. The government says the FY2025 group purchase cut equipment and installation costs by about 20% compared with estimated market prices (Tokyo Metropolitan Government: group purchase). Prices may differ by round.

Many prefectures, cities and wards run their own battery subsidies, often on top of the national and Tokyo ones. Amounts and budgets change every year and run out early, so we do not list them. Search your municipality's site for 蓄電池 補助金 and ask whether it can be combined with the national scheme, because the rules on combining differ.

Tokyo changed its environmental ordinance so that large housing suppliers must install solar panels on new homes they supply. It started in April 2025 and applies to suppliers who build or sell 20,000 m² of floor area supplied in Tokyo a year or more (Tokyo Metropolitan Government: new building requirements). The duty is on those large suppliers, not on the home buyer. Buyers of custom-built homes are asked to take environmental measures, and buyers of ready-built homes are asked to make an effort.

The government document describes the requirement as solar panels plus insulation and energy-efficiency performance. We found no requirement to install a battery. If you buy a new home in Tokyo, ask the builder whether it is covered and what is already installed, because a ready-made solar system is a good basis for a later battery.

Time-of-use tariffs

Japanese retailers sell plans with cheaper night hours, which suit a battery. TEPCO Energy Partner's page on the national bill support lists plans such as Yoru-Toku 8 and 12, Otoku na Night 8 and 10, Denka Jozu and a Peak Shift plan (TEPCO Energy Partner: eligible plans). The page does not describe how those plans are priced, so we do not give rates here.

A battery earns from the gap between cheap and expensive hours, and from raising your own use of solar. Compare your retailer's night price with its daytime price, include the plan's fixed charges, and check whether the plan assumes certain equipment (for example a heat-pump water heater) before you count on arbitrage. We explain the method in dynamic energy contracts and how to actually save. We did not check time-of-use plans from other retailers or regions, and we could not confirm current prices.

Standards and product safety

Japan's rules for fixed home batteries are mostly set through standards and the subsidy conditions, and we found no single law that sets one safety mark for them. METI's power station document lists "stationary storage systems" as covered by JIS C 4412, and a prefectural subsidy guide names JIS C 4412 as the system safety standard for lithium-ion home systems under 20 kWh, with battery safety to JIS C 8715-2 or IEC 62619 (METI: portable power station interim summary; Wakayama Prefecture: guide for home storage systems).

The same guide asks lithium-ion systems under 10 kWh to pass a third-party review against the seismic countermeasure standard for storage systems (蓄電システムの震災対策基準), and asks for a manufacturer warranty and a cycle-test performance of at least 10 years each (Wakayama Prefecture). It is a prefectural document and not the national text, so treat it as an example of what buyers are asked to check. The performance label under JIS C 4414 (initial effective capacity, rated output, runtime, service life) lets you compare makers (JEMA: JIS C 4414 label).

We could not confirm whether the Electrical Appliance and Material Safety Act (PSE) covers a fixed home storage system as such. The prefectural guide refers to the Act's technical standards interpretation and to a registered inspection body, but we did not read the Act. Ask the seller which certificates the product holds, and ask for copies.

Grid protection is separate. JEMA says that for low-voltage connection the application includes a certificate for the inverter or battery, with a list of protection settings, or a test report if the product is not certified, and that certified products are those approved under schemes such as JET (JEMA).

Installing and connecting a battery

Under the Electricians Act, only a person who holds an electrician licence may carry out electrical work on general-use electrical installations such as homes, apart from minor work the ministry exempts. The penalty for breaking that rule in the text we read is imprisonment of up to three months or a fine of up to ¥30,000 (House of Representatives: Electricians Act). The text appears to be an older version, so check the current law on e-Gov.

Under the Electrical Contractors Act, a business that does electrical work for others must be registered or notified, and a registered contractor needs a chief electrician at each office. Registration for work on general-use installations must be renewed every five years (METI: electrical work safety). Ask your installer for its registration number and licence details.

Before installation, your installer normally files the grid connection consultation with the local grid company, with a single-line diagram, earth-leakage breaker data and the certificates for the equipment (JEMA). We could not confirm the rules for exporting power from a battery to the grid, so ask the grid company and installer how your system will be set up, including whether it can export from the battery at all.

Fire rules are set by local fire prevention ordinances. As an example, Atsugi city amended its ordinance from 1 January 2024: stationary batteries of 10 kWh or less fall outside the rules, those above 10 kWh up to 20 kWh are generally exempt if they have fire-prevention measures, and units above 20 kWh are covered and must be notified. Batteries must also normally keep 3 metres from buildings unless fire-spread prevention is in place, and outdoor units need weather protection (Atsugi city: fire ordinance amendment). Other municipalities may differ, and the document does not say how an individual home is classified, so ask your local fire department.

Our guides on how to choose a home battery and what size home battery you need help you prepare questions for the installer. Ask in writing about warranty, DR terms, backed-up circuits and who handles the subsidy paperwork.

Backup power and V2H

V2H (vehicle-to-home) lets an electric car supply the house. The Clean Energy Vehicle centre's FY2025 supplementary programme pays, for an individual home, half the purchase price, up to ¥750,000 for the charger-discharger equipment and up to ¥550,000 for installation. The applicant must own, or have ordered, an electric vehicle, plug-in hybrid or fuel cell vehicle, the address must match, and holiday homes are not eligible. The application window was 17 July to 30 September 2026, it has closed, and the centre says no later window is planned this year (CEV centre: V2H subsidy guide).

A V2H charger replaces or adds to a fixed home battery, and it needs a car that supports discharging. Check that your car and the charger are on the compatibility lists, and what the car maker's warranty says about daily discharging. We did not review warranties or compatibility.

Portable power stations versus a home battery

Portable power stations (ポータブル電源) are very popular in Japan for disasters and camping. A portable power station is a movable battery with sockets: you plug devices into it. A fixed home battery is wired into the house by an electrician, connects to the grid and solar through a power conditioner, and can run chosen circuits. They solve different problems.

Choose a portable power station if you want to charge a phone, run a light, a fan, a router or a small appliance for a few hours, camp, or keep a spare for an outage. Choose a home battery if you have solar and want to use your own power in the evening, want to shift consumption to cheap hours, or want selected circuits to carry on during an outage. A portable power station cannot be wired into the house. METI's safety requirements say not to connect it to household wiring, and to keep it ventilated and away from heat (annex F in the interim summary).

On rules, METI says portable power stations are currently outside the PSE law, and its safety requirements, published as an interim summary in February 2024, are voluntary guidance for makers (METI: interim summary; METI: portable power station page). By contrast, mobile batteries used as external power for electronic devices have been covered by PSE since 1 February 2018 (METI: Q&A on portable lithium-ion batteries), for lithium-ion batteries with an energy density of 400 Wh per litre or more (Fire and Disaster Management Agency: lithium-ion batteries). We could not confirm whether the rules for portable power stations changed after April 2024, so ask the seller for the certificates.

Safety needs attention. A June 2026 Consumer Affairs Agency notice on serious product accidents includes a fire involving a portable power station in a car and a recall of a model of that type (Consumer Affairs Agency: serious accident notice, 26 June 2026). Check recall lists for any unit you own, do not leave a unit in a hot car, and do not use one to power life-support equipment, as METI's requirements warn.

Some cities pay for backup power for people who depend on medical equipment at home. Kyoto's FY2026 scheme covers portable power stations with sine-wave AC output of 300 W or more up to ¥80,000, from 1 April 2026 to 28 February 2027 (Kyoto city: emergency power equipment subsidy). Yokohama pays up to ¥60,000 (¥54,000 for taxable households) for residents who use a home ventilator or APD dialysis (Yokohama city: emergency power equipment). Both schemes target people with medical needs, not the general public. We found no national subsidy for portable power stations, and we did not review other cities.

What a home battery costs

We do not give market prices, because they vary by maker, size and installer, and we found no official price list. The subsidy rules give one official reference: for the national scheme the equipment and installation must not exceed ¥125,000 per kWh excluding tax, which is a ceiling for eligibility and not a market average (SII). Tokyo's group purchase reports a cost reduction of about 20% against estimated market prices in FY2025 (Tokyo Metropolitan Government).

Ask for at least two written quotes that show the usable capacity, the price excluding and including tax, the installation work, the warranty, and which subsidies the seller will file for you. Our guide to how a home battery saves money shows how to turn a quote into a payback estimate.

Outside Japan

Rules, tariffs and incentives for home batteries differ from country to country, so do not apply the figures on this page to a home elsewhere. We are adding guides for other countries to this section.

Common questions about Japan

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