This is a translation of the Japanese original. The Japanese version is authoritative; figures follow Japanese tax law.
In 2026 the subsidy for an inner window runs from 22,000 yen to 140,000 yen per window. Only two performance grades are left: P, with a thermal transmittance of 1.1 or lower, and S, at 1.5 or lower. Grade A, which existed until last year, has been abolished. The cap is 1,000,000 yen per dwelling, half the 2,000,000 yen of 2025. Only registered contractors may apply; the person living in the home cannot. Reservations close on 16 November 2026 and grant applications on 31 December. Just 25% of the national budget has been used so far, but the top-ups in Saitama Prefecture and Nagoya City are already over.
The short answer: 22,000 to 140,000 yen per window, up to 1,000,000 yen per dwelling
The subsidy is a fixed amount for each window, not a share of the work cost. It is set by the performance grade, the size of the window, and whether the home is a detached house or a flat.
| Grade | Housing type | Extra large 4.0 sqm or more | Large 2.8-4.0 sqm | Medium 1.6-2.8 sqm | Small 0.2-1.6 sqm |
|---|---|---|---|---|---|
| P (thermal transmittance 1.1 or lower) | Detached | 140,000 yen | 89,000 yen | 58,000 yen | 36,000 yen |
| Flat | 152,000 yen | 98,000 yen | 64,000 yen | 40,000 yen | |
| S (thermal transmittance 1.5 or lower) | Detached | 76,000 yen | 52,000 yen | 34,000 yen | 22,000 yen |
| Flat | 83,000 yen | 57,000 yen | 37,000 yen | 24,000 yen |
Source: Advanced Window Renovation 2026 programme (先進的窓リノベ2026事業), "Details of eligible work: inner window installation"[Ministry of the Environment]. Low-rise flats use the same unit prices.
- The cap is 1,000,000 yen per dwelling. Splitting the work into several applications does not raise it.
- Each application needs a subsidy of 50,000 yen or more. Two inner windows in the same opening still count as one.
- Reservations run to 16 November 2026 and grant applications to 31 December[Guide to grant applications]. The programme ends the moment the budget is exhausted.
Three changes in 2026: grade A dropped, the cap halved, an extra-large size added
The change that bites hardest is that grade A for inner windows (thermal transmittance 1.9 or lower) is no longer eligible[Ministry of the Environment]. Choose from last year's catalogue and some products now attract nothing at all. Grade A survives only for glass replacement, outer window replacement and door replacement.
| Item | 2025 programme | 2026 programme |
|---|---|---|
| Cap per dwelling | 2,000,000 yen | 1,000,000 yen |
| Performance grades for inner windows | Three grades (grade A included) | Two grades, P and S |
| Window sizes | Large, medium, small | Four, with extra large added |
Source: Ministry of the Environment, "Outline of the Advanced Window Renovation 2026 programme"[Ministry of the Environment].
The budget has fallen too, from 135.0 billion yen to 112.5 billion yen. The halved cap, though, barely matters for inner-window-only work. At grade S in the large size it takes 20 windows to reach 1,040,000 yen. What the cap bites into is the bigger jobs that replace the outer windows throughout a house.
The contractor applies. You cannot apply yourself
Only a registered "Window Renovation contractor" (窓リノベ事業者) may apply[Window Renovation 2026, application procedure]. The owner cannot be the applicant. Choosing the contractor is choosing the subsidy.
- Check that the firm is registered. The search page of the Housing Energy Saving 2026 Campaign (住宅省エネ2026キャンペーン) lists them. If a firm is not there, ask it directly.
- Sign the works contract. Work started before the contract is not eligible.
- Take the before photographs. There is no waiver form this year, and a window nobody photographed gets nothing.
- Start the work. A reservation is valid for three months from submission, or until 31 December, whichever comes first.
- The contractor files the grant application once the work is finished. The desk closes on 31 December at the latest.
- Receive the money. It is set against the bill or paid in cash. A window that received the subsidy carries a ten-year restriction on disposal.
Check where the line falls on eligible work before you sign.
Inner window work that is eligible
- Fitting an inner window inside an existing window
- Replacing an existing inner window with a new one
- Placing it parallel to the outer window, within 50 centimetres inside the opening
Work that is not eligible
- Fitting three or more inner windows to a single outer window
- Second-hand or display products, or owner-supplied windows (installation only)
- Windows that do not face outside air, and door-only work
What runs out first is the local top-up. The national budget is still at 25%
As of midnight on 23 September 2026, only 25% of the national Window Renovation budget had been claimed[Window Renovation 2026, share of applications]. Applications through August came to 21.8 billion yen in total. It is the municipalities that are in a hurry. Saitama Prefecture closed on 29 July and Nagoya City on 8 September.
| Municipality | Amount | Combined with the national subsidy | Deadline and status |
|---|---|---|---|
| Tokyo | Up to 2,000,000 yen per dwelling. 65,000 yen for a large grade-S inner window | Yes | Grant applications from 30 June 2026 |
| Setagaya Ward | Up to 200,000 yen | Yes | Second round due to open on 1 October |
| Kanagawa Prefecture | One third of eligible costs, or 150,000 yen | Yes (depends on the municipality) | Until 30 September 2026 |
| Saitama Prefecture | A top-up on the national programme | Combination assumed | Closed on 29 July 2026 |
| Yokohama City | Up to 1,200,000 yen (1,500,000 yen when moving in) | Check first | Until 28 February 2027 |
| Nagoya City | Up to 100,000 yen for insulating window work | Check first | Closed on 8 September 2026 |
| Kyoto City | Two thirds of eligible costs, 1,200,000 yen per dwelling | Check first | Until 30 November 2026 |
| Sendai City | Up to 100,000 yen for windows | Check first | By lottery. Third round from 1 December |
Source: the official pages of each municipality (listed at the end). For Yokohama, Nagoya, Kyoto and Sendai we could not find an explicit statement on combining with the national subsidy. Ask the desk.
The rule on combining is simple. The same window cannot receive the national subsidy twice[Window Renovation 2026, eligibility]. The Mirai Eco Housing 2026 programme (みらいエコ住宅2026事業) can be combined if the parts of the building are kept separate, and municipal schemes can be combined unless they are paid for out of national funds.
Once the budget runs dry, work on openings becomes eligible under the Mirai Eco Housing 2026 programme[MLIT, Mirai Eco Housing 2026]. The whole picture of the four programmes is in Renovation subsidies 2026, and Tokyo's housing subsidies in Tokyo's solar, battery and V2H subsidies.
A worked example: four inner windows, 208,000 yen in subsidy, about 230,000 yen out of pocket
The common case is fixing only the windows of the cold rooms. Take a detached house with four grade-S inner windows in the large size.
- Subsidy: 52,000 yen x 4 windows = 208,000 yen (clears the 50,000 yen floor and the 1,000,000 yen cap)
- Work cost, as a guide: about 109,500 yen x 4 windows = about 438,000 yen
- Out of pocket: 438,000 yen - 208,000 yen = about 230,000 yen (about 53% of the work cost)
The unit subsidy and the number of windows match the model case published by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT)[MLIT]. The cost per window is our own apportionment of Tokyo's "1,205,000 yen for 11 windows" and is not a figure published by Tokyo.
In Tokyo the metropolitan grant sits on top. On Tokyo's own estimate, fitting grade-S inner windows to 11 windows in a detached house of about 120 sqm costs 1,205,000 yen[Tokyo, energy-saving renovation programme]. Tokyo pays 558,000 yen and the state 452,000 yen, leaving 195,000 yen out of pocket. With energy bills falling by about 23,000 yen a year, the payback is put at about 8.5 years.
When payback takes the best part of a decade, insulation work is less an investment than an improvement to daily life.
Taking the subsidy pushes the tax relief further away: the 500,000 and 600,000 yen floors
Four inner windows on their own reach neither the income tax credit nor the reduction in fixed asset tax. The subsidy is deducted from the amount used in the test[MLIT]. Take 208,000 yen of subsidy off the 438,000 yen of work and 230,000 yen is left. That clears neither the "over 500,000 yen" for income tax nor the "over 600,000 yen" for fixed asset tax.
| Relief | Floor (after deducting the subsidy) | Effect | Deadline and procedure |
|---|---|---|---|
| Income tax credit (energy-saving renovation) | Standard cost over 500,000 yen | Up to 625,000 yen (675,000 yen including solar) | Until 31 December 2028. File a tax return with a certificate of renovation work (year-end adjustment will not do) |
| Reduction in fixed asset tax | Work cost over 600,000 yen | One third off the following year's tax (on 120 sqm, for one year only) | Until 31 March 2031. File within three months of completion |
Sources: National Tax Agency No.1219[National Tax Agency], MLIT[MLIT], Tokyo Metropolitan Bureau of Taxation[Tokyo Bureau of Taxation]. Fixed asset tax is handled by the municipality.
To get over the floors you would have to insulate the walls, floor and ceiling at the same time. MLIT's model case is a 6,820,000 yen renovation, with 1,104,600 yen of subsidy, 413,510 yen of income tax relief and 29,800 yen off the fixed asset tax. For inner windows alone it is quicker to treat the subsidy as the whole of the benefit. The full picture of the reliefs is in the table in Renovation subsidies 2026.
Is the subsidy itself taxed? The 500,000 yen deduction for occasional income
A national subsidy an individual receives for home renovation is in principle occasional income[National Tax Agency No.1490]. There is, however, a special deduction of 500,000 yen, so with no other occasional income nothing up to 500,000 yen is taxed. The 208,000 yen for four inner windows is nothing to worry about.
- An employee need not file if income other than salary is 200,000 yen or less. Occasional income is half of "the amount received minus 500,000 yen", so a subsidy of up to 900,000 yen still falls below the filing threshold.
- Even above 500,000 yen, the special rule excluding national subsidies from gross revenue (Income Tax Act, Article 42) may allow the amount to be left out of occasional income.
We could not find any document naming the Window Renovation subsidy as covered by that special rule. What the National Tax Agency does name is the Sumai Kyufukin housing benefit and the like. Where the sums are large, check with the tax office.
The order of moves is fixed. Check that the firm is registered, get a quote for grade P or S products, and have the before photographs taken. After that all you need is your municipality's deadline. Other subsidies are collected in Delivery box subsidies 2026 as well.
FAQ: applying and the deadlines
Can I apply for the subsidy myself?
No. Only a "Window Renovation contractor" registered with the secretariat can apply. The subsidy comes back to you as a credit against the bill or in cash.
What if the before photographs were forgotten?
That work gets no subsidy. The 2026 programme has no waiver form for before photographs and no substitute document. Check with the contractor before work starts.
If the national budget runs out, do window subsidies disappear?
No. Once Window Renovation reaches its cap, work on openings becomes eligible under the Mirai Eco Housing 2026 programme. As of 23 September, 25% of the budget had been used.
Can I take both the national and the municipal subsidy?
Yes, as long as the municipal scheme is not funded from the national budget. What Tokyo forbids is only overlap within its own and the public corporation's schemes, so combining with the national subsidy is possible. Where nothing is stated, ask the desk.
Reference links (sources)
- Window Renovation 2026, eligible work: inner window installation - the table of amounts
- Same, eligibility (housing) - cap, floor and combining
- Same, application procedure (housing) - only registered contractors apply
- Same, share of the budget claimed - 25%
- Same, guide to grant applications - dates and before photographs
- Ministry of the Environment, outline of the programme - the 112.5 billion yen budget and the changes
- Mirai Eco Housing 2026 programme - the fallback once the budget is reached
- National Tax Agency No.1219, energy-saving renovation work - over 500,000 yen after the subsidy
- National Tax Agency No.1490, occasional income - the 500,000 yen special deduction
- MLIT, tax relief for renovation - up to 625,000 yen
- MLIT, consumer leaflet - the four-window example
- Tokyo Bureau of Taxation, reduction in fixed asset tax - over 600,000 yen, within three months
- Tokyo, energy-saving renovation programme - up to 2,000,000 yen per dwelling
- Setagaya Ward, eco housing subsidy - up to 200,000 yen
- Kanagawa Prefecture, energy-saving renovation subsidy - closes 30 September
- Saitama Prefecture, window insulation renovation support - closed
- Yokohama City, insulation renovation subsidy for existing homes - up to 1,500,000 yen
- Nagoya City, decarbonisation subsidy - closed
- Kyoto City, insulation renovation subsidy - until 30 November
- Sendai City, healthy energy-saving housing subsidy - up to 100,000 yen for windows
Note: the work cost per window and the out-of-pocket figure are our own estimates, and actual costs vary with the quotation. On the taxation of subsidies, please check with the tax office.
