Leave Your Solar Panel Installation Work in Bunkyo, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and battery installation in
Bunkyo, Tokyo,
Kakeru Koumuten is at your service!
Kakeru Koumuten is a company specializing in exterior renovations.
As a strong company in roofing work, we are entrusted withsolar panel and battery installation considering roofs and waterproofing!
“How to Choose a Solar Panel Contractor in Bunkyo, Tokyo”
“Costs for Solar Panel and Battery Installation”
“Subsidies Available for Solar System Installation in Bunkyo, Tokyo”
We will also explain the above three points!
Installing solar panels carries risks such as“the occurrence of leaks” and other troubles.
To ensure you do not regret your solar panel installation, we recommend obtainingquotes from about three companies!
Table of Contents (tap to open/close)
- Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Bunkyo, Tokyo
- Roof Inspection Before Installing Solar Panels
- Possible Subsidies and Grants Available in Bunkyo, Tokyo
- Price List for Solar Panel and Storage Battery Installation
- Breakdown of Installation Capacity, Equipment, and Construction Costs
- Self-Estimate and Profit Simulation for Solar Power Generation
- Customer Testimonials
- Case Studies of Solar Panel Installations
- How to Choose a Solar Panel Installer in Bunkyo, Tokyo
- Benefits of Introducing Solar Equipment
- Points to Consider When Introducing Solar Power Generation
- How to Choose Solar Panels
- Frequently Asked Questions About Solar and Storage Battery Installation in Bunkyo, Tokyo
- If You’re Looking for a Solar Panel Installer in Bunkyo, Tokyo, Contact Kakeru Koumuten
- Characteristics of Bunkyo, Tokyo and Points for Solar Installation
- Service Area in Bunkyo, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Bunkyo, Tokyo
Regarding why we are entrusted with solar panel installation by customers in Bunkyo, Tokyo,
“Our Unique Strengths in Solar Panel Installation That Cannot Be Imitated by Other Companies”
have received high praise from many customers.
so we would appreciate it if you could compare our estimates with those of other companies.
Because we are confident, we welcome estimates from any number of companies!
1. We Also Handle Exterior Renovations Beyond Solar Panel Installation!
Issues such as leaks that occur during solar panel installation may be caused by insufficient checks on the roof and waterproofing at the installation site.
Even if one is knowledgeable about solar panels, there are cases where the roof and waterproofing at the installation site are outside their expertise, so caution is necessary.
It is reassuring to have expertise in roofing to avoid maintenance and trouble after installation!
Kakeru Koumuten Co., Ltd. is strong in roofing work and can also detach and attach solar panels in-house, allowing for quick responses to maintenance and urgent issues after solar panel installation!
2.Facilities Specialized in Exterior Renovation
Kakeru Koumuten Co., Ltd. has organized the following warehouses and material storage areas to provide solar panel work and exterior renovations at low cost and high quality.
We have established five bases for material storage and showrooms.
In-house Ownership of Scaffolding Materials
To ensure safety during work on the roof, we own the scaffolding materials necessary for temporary scaffolding based on construction conditions, allowing us to assemble scaffolding in-house.
By conducting scaffolding work with our own scaffolding team instead of outsourcing, we can also cut costs on scaffolding work.
We own scaffolding materials for approximately 50 single-family homes!
Even if there are height differences on the site, our in-house scaffolding team will plan the scaffolding according to the local conditions.
Storage of Materials in Our Large In-house Warehouse
We store roofing materials and paints, and we can also store removed solar panels.
By ordering a large quantity of materials at once, you canpurchase materials at a lower cost!
Additionally, since we always have a stock of roofing materials, we canrespond quickly in emergencies!
In-house sorting and transportation of waste materials
The installation of solar panels often involves roofing work, generating various waste materials such as paint, wood, and metal.
By sorting and recycling waste materials, we can significantly cut waste disposal costs.
Exterior renovation dedicated showroom
In the showroom, not only can you have meetings, but you can also
check the actual foundation brackets for solar panels and see how they are installed on roofing materials!
It is also possible to simulate the revenue and installation costs when introducing solar panels!
Since roofing and exterior wall work often accompany each other, we also provide samples of roofing materials and models that explain the structure, allowing for detailed explanations!
3.All work performed by our own team
One of Kakeru Koumuten’s major strengths is its complete in-house construction.
By maintaining a consistent system from inquiry to project completion, Kakeru Koumuten can provide high-quality roof renovations at reduced costs.
Additionally, one representative will handle everything from the estimate to project completion.
Since the same person is responsible for sales and construction management, smooth communication is ensured.
We can perform consistent in-house construction from temporary scaffolding setup to exterior wall painting and roof renovations!
4. Various Permits and Skilled Workers
We have obtained construction industry licenses and permits for industrial waste collection and transportation!
We also have nationally certified sheet metal and painting technicians, and we are confident in our construction skills.
We can also handle large-scale roof projects such as factories!
5. Warranty and Aftercare
In addition to the manufacturer’s warranty for solar panel installation, we also provide our own construction warranty (leakage warranty)!
(The construction warranty for solar panel installation is 10 years. Depending on the condition of the roof before installation, we may not be able to provide a warranty unless a roof renovation is performed. The construction warranty is separate from the manufacturer’s product warranty, and the scope and conditions vary depending on the warranty details.)
Aftercare is available annually, and we send out notification DM each year.
If you have questions about the warranty, please click on the image above!
6. Flexible and Prompt Response
Our company is equipped to handle various roofing troubles and situations.
If you cannot access the roof at high places, we can utilize drones to assist!
During leak investigations, we can also conduct surveys using a thermal imaging camera.
If the power generation of solar panels decreases due to dirt, we can provide cleaning with a specialized brush.
We will respond according to your wishes.
7. Human Resource Development
To enhance skills, we create various roofing models and conduct practical training.
Since the construction methods vary depending on the shape and slope of the roof, we regularly provide technical training so that each staff member can handle various cases.
8. Creation of Easy-to-Understand Materials and Simulations
At Kakeru Koumuten, we provide not only “estimates,” “layout diagrams,” and “power generation simulations” but also a “solar construction guidebook” and a “profit and loss simulation” that takes into account loan interest rates and electricity costs.
The profit and loss simulation can be created for projected cumulative profits and losses over 20 to 30 years.
Even customers who are not familiar with solar construction will receive materials that clearly summarize important points and disadvantages!
We encourage you to obtain comparative estimates and review plans from other companies!
Roof Inspection Before Installing Solar Panels
Once solar panels are installed, they will remain on the roof for 20 to 30 years.
Confirming “Is it safe to install them directly on the current roof?” before installation is the key point to prevent leaks and unnecessary expenses!
Kakeru Koumuten, which specializes in roofing work, has summarized the items to check before installation.
| 1. Types of Roofing Materials and Age | The fixing method varies depending on the roofing materials such as slate, tiles, metal roofs, and flat roofs (rooftop waterproofing). If the remaining lifespan of the roofing material is short, we may suggest roof renovation first. |
| 2. Condition of Substrate and Waterproof Sheet | If the sheathing boards or roofing (waterproof sheet) under the roofing material are damaged, it will affect the fastening strength and waterproofing. We will also check for any signs of leaks. |
| 3. Orientation, Slope, and Shadows of the Roof | The orientation and slope of the roof surface, as well as shadows from neighboring houses, trees, and utility poles, will affect the power generation. We will create a layout diagram from the drawings and the site, and you can check it with a power generation simulation. |
| 4. Shape of the Roof and Usable Area | The number of panels that can be installed (installation capacity) is determined by the shape and size of the roof. Since the number of panels that can be installed varies depending on the panel size, we will compare based on the total output of the roof. |
| 5. Fixing Method and Waterproofing Details | We will check whether the method involves drilling holes in the roofing material for fastening or using brackets to secure the roofing material. The fixing method varies by technique, so please confirm the waterproofing treatment method for the fixed parts during the estimate. |
| 6. Weight of the Roof | The roof will become heavier due to the panels being installed. After investigating the existing roof, substrate, and load-bearing capacity, switching to lighter roofing materials may also be an option if necessary. |
| 7. Installation Location of Equipment and Wiring | We will confirm the installation location of the power conditioner and storage battery, as well as the wiring route to the distribution board. The length of the wiring will also affect the cost. |
| 8. Ease of Scaffolding Setup and Delivery Routes | If there is a height difference on the site, planning for scaffolding and the delivery routes for equipment and materials may require some ingenuity. The width of the front road and any steps on the site will also be checked during the site survey. |
Fixing Methods and Confirmation Points by Roofing Material
| Roof Material | Main Fixing Method | Pre-Installation Check Points |
|---|---|---|
| Slate Roof | Varies by method (e.g., fixing brackets to the roof material and substrate with screws) | Waterproof treatment of fixing parts, cracks or deterioration of slate, condition of the substrate. If deterioration is advanced, consider roof overlay (cover method) or replacement first. |
| Tile Roof | Fixed with brackets and methods suitable for the type of tile (even methods that do not drill holes in the tiles will fix to the substrate) | Type and condition of tiles, substrate, load-bearing capacity. Depending on the investigation results, there may be methods to replace with lightweight roofing materials before installation. |
| Metal Roof (Horizontal and Vertical) | Fixed with catch-type brackets that grip the roof material (depends on the combination of roof material and brackets) | Whether the roof material and brackets are compatible, installation conditions from the roof material manufacturer. If compatible, methods that do not drill holes may be available. |
| Flat Roof / Rooftop | Fixed by installing a frame | Type and deterioration status of the waterproof layer, waterproofing around the frame. Consider in conjunction with the timing of waterproofing work. |
If you perform roof renovations 10 to 20 years after installation, there will be additional costs for removing and reinstalling solar panels. If the roof is deteriorating, it may be more cost-effective in the long run to renovate to a highly durable roofing material before installation.
Kakeru Koumuten Co., Ltd. specializes in roofing work and can also handle the removal and reinstallation of solar panels in-house, so please consult us according to the condition of your roof!
▶ Click here for roof renovations in Bunkyo, Tokyo
Subsidies and Grants That May Be Applicable inBunkyo, Tokyo
If you are introducing solar panels or storage batteries in Bunkyo, Tokyo, there is a possibility that the systems from the “National Government,” “Tokyo Metropolitan Government,” and your local “Bunkyo Ward” may apply.
The following information is based on the official pages of each system as of October 7, 2026. The acceptance status may change depending on the budget, so please check the latest information before contracting or starting work.
Eligibility Conditions and Application Period for Subsidy Programs
| Program | Main Eligibility Conditions | Subsidy Amount | Application Period & Status |
|---|---|---|---|
| Tokyo Metropolitan Government “Household Solar Power Generation Promotion Project” | Individuals, corporations, or management associations installing a new unused solar power system (output under 50kW, JET certification, etc.) in residential properties within Tokyo. The generated power must be used in the residential part. Pre-application is required. | Existing homes: 150,000 JPY per kW for up to 3.75 kW (maximum 450,000 JPY), 120,000 JPY per kW for over 3.75 kW and under 50 kW. New homes: 120,000 JPY per kW for up to 3.6 kW (maximum 360,000 JPY), 100,000 JPY per kW for over 3.6 kW. |
For the fiscal year 2026, pre-applications are being accepted from May 29 (will end once the budget is reached). From the pre-application for fiscal year 2026, submission of certificates issued by financial institutions will be mandatory during the performance report. |
| Tokyo Metropolitan Government “Household Storage Battery Promotion Project” | Owners of eligible equipment (storage batteries registered with SII) excluding national and local governments. Installation must occur between April 1, 2026, and March 30, 2031. If pre-applying after October 1, 2026, only products registered with the national SII for fiscal year 2026 are eligible. | Storage battery package: 100,000 JPY per kWh (maximum 1,200,000 JPY per household). Additional for participating in DR demonstration (100,000 JPY per unit; 150,000 JPY per unit if energy management equipment is installed). Expansion of storage battery units: 60,000 JPY per kWh (maximum 720,000 JPY per household). |
For the fiscal year 2026, pre-applications are being accepted from May 29. Grant applications and performance reports will be accepted from June 30. |
| Bunkyo Ward “New Energy and Energy Conservation Equipment Installation Cost Subsidy Project” | Individuals must reside within the ward. Solar power systems are eligible for individuals and management associations, while household storage systems are eligible for individuals, management associations, and small businesses. Applications must be made after installation (post-application), and all eligible expenses must be paid in full on the application date. | Solar power systems: 70,000 JPY per kW (maximum 350,000 JPY). Household storage systems: 20,000 JPY per kWh (maximum 100,000 JPY). Power conditioners (only for existing updates): 25% of eligible expenses (excluding tax, maximum 100,000 JPY). |
The application period is determined based on the installation date (e.g., installations in October 2026 must apply by January 4, 2027). Applications will close even within the application period if the budget is reached. |
| National Government “DR Household Storage Battery Project” (Fiscal Year 2025 Supplement) | Newly introducing household storage systems that can be utilized for DR (demand response) with registered products. | Calculated based on an initial effective capacity of 34,500 JPY per kWh (subsidy rate within 30%, maximum 600,000 JPY per application). | The budget was reached on May 29, 2026, and the public offering has ended (there are no plans to reopen the public offering, and applications cannot be made at this time). |
| National Government “Mirai Eco Housing 2026 Project” (Renovation) | Storage batteries are one of the eligible facilities, but they must be combined with essential works such as insulation renovations of windows (openings) and structures; applications cannot be made for the installation of storage batteries alone. Solar panels are not included in the eligible equipment | Storage battery: 96,000 JPY/unit | Applications will end once the budget limit is reached. As of October 5, 2026, the application amount for renovations is displayed as 8% of the budget on the official website. Please check the application status on the official website. |
The Tokyo solar and storage battery subsidy program requires prior application. For storage batteries applied for after October 1, 2026, only products registered with the national SII will be eligible, and the equipment requirements will change. The subsidy in Bunkyo Ward is a post-application system where applications are made after the equipment is installed, within the application period corresponding to the installation date. Eligibility conditions, application procedures, and the possibility of combining with other programs vary by system, and applying does not guarantee that subsidies will be granted, so please confirm before contracting and starting work.
Kakeru Koumuten Co., Ltd. will provide guidance on eligibility conditions and application periods for each program after confirming them.
National Subsidy “DR Home Storage Battery Project (Support Project for Introducing Home Storage Systems for DR Resource Implementation)”
The national government has been implementing the “DR Home Storage Battery Project” to support the installation of home storage batteries.
This program targets those who are introducing newly registered storage systems that can be utilized for demand response (DR), and in the fiscal year 2025 supplementary budget, the subsidy amount was determined based on a standard amount of 34,500 JPY per 1 kWh of initial effective capacity, with a subsidy rate of up to 30% and a maximum of 600,000 JPY per application. There are conditions such as that contracts or orders made before the grant decision are not eligible.
However, the fiscal year 2025 supplementary budget applications reached the budget limit on May 29, 2026, and the public offering has ended. The official website also states that there are no plans to resume the public offering, and applications are currently not possible. Please check the official website for future public offerings.
Additionally, there are currently no subsidies confirmed for the installation of solar panels on existing homes.
👉 Click here for the official website of the DR Home Storage Battery Project
Tokyo “Promotion Project for Introducing Solar Power Generation in Homes”
This subsidy is for those who are newly installing unused solar power generation systems in residential homes in Tokyo. The simultaneous installation of storage batteries is not a condition.
● Existing homes: For systems under 3.75 kW, 150,000 JPY per kW (maximum 450,000 JPY); for systems over 3.75 kW and under 50 kW, 120,000 JPY per kW
● New homes: For systems under 3.6 kW, 120,000 JPY per kW (maximum 360,000 JPY); for systems over 3.6 kW and under 50 kW, 100,000 JPY per kW
● Additional amounts for rooftop frame installation and waterproofing work are also available.
Eligible systems are those installed in residential homes in Tokyo using unused panels that have obtained JET certification, with an output of less than 50 kW, and used in the living area. The process involves making a prior application and then applying for the grant after installation. Starting from the prior application for fiscal year 2026, submission of documents such as certificates issued by financial institutions during the performance report is now mandatory.
The official page of Tokyo states that pre-registration is being accepted from May 29, Reiwa 8. It will end once the budget is reached, so please check the official page for the registration status.
👉 Here is the official page of Tokyo (Cool Net Tokyo)
Tokyo’s “Household Battery Installation Promotion Project”
This is a subsidy for the installation costs of battery systems aimed at increasing self-consumption of electricity generated by solar power and improving energy independence during emergencies.
●Battery package: 100,000 yen per kWh (up to 1,200,000 yen per household)
●Additional for participating in DR demonstration: 100,000 yen per unit (150,000 yen per unit if energy management equipment is installed)
●Expansion of battery unit: 60,000 yen per kWh (up to 720,000 yen per household)
Eligible applicants are owners of the subsidized equipment (excluding national and local governments), and installation must occur between April 1, Reiwa 8 and March 30, Reiwa 11. If pre-registration is done after October 1, Reiwa 8, only products registered in the national SII for Reiwa 8 are eligible.
The official page of Tokyo states that pre-registration is being accepted from May 29, Reiwa 8. For detailed conditions such as combinations with solar power generation, please check the official page.
👉 Here is the official page of Tokyo (Cool Net Tokyo)
Bunkyo Ward “New Energy and Energy Conservation Equipment Installation Subsidy Project” (Reiwa 8 Fiscal Year)
This subsidy is for those installing solar power generation systems or home battery systems in residential areas within the ward. Individuals must have an address within the ward, and solar power generation systems are eligible for individuals and management associations, while home battery systems are eligible for individuals, management associations, and small businesses. This is a post-application system where applications are made after installation, and documents must be mailed within the application period corresponding to the installation date.
●Solar power generation system: 70,000 yen per kW (up to 350,000 yen)
●Home battery system: 20,000 yen per kWh (up to 100,000 yen)
●Power conditioner (only for replacement of existing units): one-fourth of eligible expenses (excluding tax) (up to 100,000 yen)
The solar power generation system must use modules certified by JET or IECEE-PV-FCS, and the generated electricity must be used in the residence. The battery system must be a product designated by SII and must be connected to solar power generation or Enefarm. Conditions include that the eligible expenses must be fully paid on the application date, and applications for the same residence and equipment can only be made once per fiscal year.
The application period is determined by the installation date, and the official page states that for installations in October, the deadline is January 4, Reiwa 9; for November, it is February 1, Reiwa 9; and for December, it is March 1, Reiwa 9. Applications will be accepted within the budget, and if the budget is reached, acceptance will end even within the application period. It is possible to apply for subsidies from both the national and Tokyo governments, but the total amount of subsidies cannot exceed the expenses incurred for the installation.
Since the acceptance status and detailed requirements may change, those considering applying should check the official page.
👉 Here is the official page of Bunkyo Ward
Solar Panel Installation & Battery Installation Price List
⇧Service Menu | For Costs Related to Solar Panel Installation & Battery Installation, Click Here
⇧Service Menu | For Costs Related to Solar Panel Removal & Water Heater Dismantling, Click Here
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and batteries should be confirmed by separating them into “Equipment Costs (Device Costs)” and “Construction Costs”.
Even for the same “Complete Solar Panel Installation,” the amount can vary significantly depending on the installation capacity, equipment grade, and roof condition.
Understanding Installation Capacity (kW) and Battery Capacity (kWh)
The installation capacity of solar panels is determined by “Output of One Panel (W) × Number of Panels”, with the unit being kW (kilowatt). Battery capacity is compared in kWh (kilowatt-hour), which represents the amount of electricity that can be stored.
The amount of kW that can be placed on a roof varies for each house depending on the shape, orientation, and size of the roof. At Kakeru Koumuten, we create layout diagrams from blueprints and on-site surveys to present the installation capacity.
On our pricing page, we list solar panel installation costs as approximately 800,000 JPY to 1,200,000 JPY for 3 to 5 kW, and 1,200,000 JPY to 1,900,000 JPY for 6 to 10 kW. (These are just estimated amounts and may vary based on factors such as wiring length, scaffolding range, existing roofing materials, and panel layout.)
▶ Installation Menu | Costs for Solar Panel and Storage Battery Installation
Items to Confirm in the Estimate (Cost Verification)
When comparing estimates, it’s common to compare different capacities and equipment. Please check if the following items are clearly stated in each company’s estimate!
| 1. Solar Panels | Manufacturer, model number, output per panel (W), number of panels, and total installation capacity (kW) should be listed. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, and installation location (indoor/outdoor). Also confirm if it is a type that controls the storage battery together. |
| 3. Storage Battery | Manufacturer, model number, capacity (kWh), range usable during a power outage (whole house or specific circuits), and installation location. |
| 4. Mounting Frame and Hardware | Name of the hardware suitable for the roofing material and the method of securing it (whether it involves drilling holes or clamping). |
| 5. Wiring and Electrical Work | Wiring route and length, work around the distribution board, and whether there is a monitor to check the power generation amount. |
| 6. Roof Reinforcement and Waterproofing | Details of waterproofing treatment at the fixed points, and whether necessary roof repairs and substrate reinforcements are included. |
| 7. Applications | Extent of support for applications to the power company, certification application for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Scope and quantity of scaffolding. If roof work and exterior painting are done simultaneously, check that the same scope and quantity are not double-counted. |
| 9. Removal and Disposal | Whether the removal of existing solar thermal water heaters or old panels and disposal costs for waste materials are included. |
| 10. Tax Classification and Warranty | Whether the price includes tax or not, conditions under which additional costs may arise, and details and duration of manufacturer and workmanship warranties. |
If the capacities are different, both the price and power generation will change. Kakeru Koumuten Co., Ltd. welcome comparisons of estimates, so if you bring estimates from other companies, we can explain the differences item by item!
Self-Estimate and Profit Simulation for Solar Power Generation
With the simulator above,
you can obtain an estimated quote and a financial simulation for up to 30 years!
If you know the total installation capacity of solar panels on the roof and the capacity of the storage battery, you can get an estimated quote and financial simulation!
*The simulation results are estimates. Actual financial results may vary based on assumptions such as electricity rates, self-consumption ratios, selling prices, and costs for equipment inspection and replacement.
Customer Feedback
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customer reviews
Asao-ku, Kawasaki City | We received reviews about the ridge cap and rain gutter replacement work!
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customer reviews
Kohoku-ku, Yokohama | We received reviews about the roof overlay (cover method)!
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customer reviews
Kohoku-ku, Yokohama | We Received Reviews About Exterior Painting!
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customer reviews
Hodogaya-ku, Yokohama | We received reviews about our exterior fence construction!
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customer reviews
Tsurumi-ku, Yokohama | We received reviews about roof and exterior wall painting, as well as metalwork and rain gutter replacement work!
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customer reviews
Higashiyamato City, Tokyo | We received reviews about exterior painting and roof overlay (cover method)!
Case Studies of Solar Panel Installations
| Construction Details |
| Solar Panel Installation Battery Installation |
| Existing Roofing Material |
| Horizontal Metal Roof (Super Galtect) |
| Installation Capacity |
| Solar Panel: 4.3kW Battery: 5kWh |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Details |
| Fixed using catch type hardware gripping the horizontal metal roof (Catch Method) |
| Price Range |
| 2,200,000 JPY～2,300,000 JPY *Due to the grant being provided, the actual burden amount is approximately 1,000,000 JPY Estimated recovery period for construction costs: about 8 to 9 years (self-consumption) *The grant amount and recovery estimate are based on the system and calculations at the time of construction and may differ under the current system. |
| Construction Period |
| Approximately 3 days |
| Completion Month |
| April 2025 |
| Inquiry Details |
| I am considering the installation of solar panels and storage batteries. I heard that grants are available, and I would like to know how much can be provided. |
Our Proposal
We visited to provide an estimate and created a layout diagram for the solar panels based on the drawings!
The layout diagram shows the arrangement of solar panels when placed on the roof.
Since we can also determine the installation capacity, it allows for power generation simulations and financial simulations.
We have also understood the expected amount of the grant, so we explained it to the customer along with the estimate!
How to Choose a Solar Panel Installation Contractor in Bunkyo, Tokyo
There are many solar panel installation contractors available in Bunkyo Ward, Tokyo, and you may be unsure which contractor to choose.
Therefore, when requesting solar panel installation and battery storage installation work, let’s confirm the following four points.
● Have extensive knowledge not only about solar panels but also about roofs
● Confirm the existence of warranties and aftercare services
● Obtain estimates from multiple contractors (three companies is a guideline)
● Check if they provide support for subsidy applications
By confirming the above four points, you will be able to choose a reliable contractor.
Knowledge about roofs as well as solar panels
Improper installation of solar panels can sometimes be caused by a lack of knowledge and verification regarding roofs and waterproofing.
While knowledge about solar panels is certainly important, understanding the roof and waterproofing where the solar panels will be installed is also crucial.
⚠︎Examples of troubles caused by insufficient verification of roofs and waterproofing
・Solar panels were installed on a severely deteriorated roof, leading to leaks
・Solar panels were installed on a roof with a short lifespan, requiring remodeling for removal and reinstallation within a few years
・Misjudging the type of waterproofing led to incorrect treatment and subsequent leaks
and more
When installing solar panels, understanding the condition and type of the existing roof allows you to avoid unnecessary expenses and unexpected troubles.
▶ Go to “Roof Verification Before Installing Solar Panels” in this article
Confirm the existence of warranties and aftercare services
When choosing a solar installation contractor, let’s confirm the existence of warranties. It is important to check not only the duration of the warranty but also the coverage, exclusions, and cost conditions.
While the solar panels and battery storage units come with manufacturer warranties, it is also important to check for the existence of a workmanship warranty in case leaks occur after installation!
For contractors that offer a workmanship warranty, if leaks occur after installation, they may cover the repairs under the warranty if it falls within the warranty period and conditions.
Additionally, some contractors offer aftercare services separate from the warranty, so be sure to check if the contractor you are considering has aftercare services.
Since abnormalities or damage on the roof can be in hidden areas, you may not notice them yourself.
By conducting inspections of hidden areas during aftercare maintenance, you can more easily detect abnormalities early and prevent major repairs or failures!
At Kakeru Koumuten Co., Ltd., the installation of solar panels comes with a leak warranty as part of our workmanship warranty. (The warranty for solar panel installation is 10 years, and depending on the condition of the roof before installation, we may not be able to provide a warranty unless roof renovation is performed.)
We also provide aftercare maintenance, sending out annual DM!
After checking the DM, if you wish, we will visit for aftercare maintenance!
Obtain estimates from multiple contractors (3 companies as a guideline)
When requesting the installation of solar panels, let’s obtain estimates from multiple contractors.
Even for the same manufacturer and the same construction content, costs may vary, and warranties and after-sales services may differ.
Additionally, obtaining multiple estimates makes it easier to negotiate prices.
To request from your preferred contractor at a lower price, we recommend obtaining estimates from multiple contractors.
When comparing estimates, please check:
“Verification of estimate items”
“Types of solar panels”
“Warranties and after-sales services”
and make a detailed comparison to make a decision! Avoid judging solely based on cost, as using lower-grade materials or skipping processes can reduce costs!
▶ To “Breakdown of Installation Capacity, Equipment, and Construction Costs” within this article
Check if they provide support for subsidy applications
There may be subsidies available for the installation of solar panels and storage batteries, but if the order of procedures is incorrect or there are deficiencies in the documents, the subsidy may not be granted.
Since there are systems like the Tokyo subsidy that require prior application, it is reassuring to have a contractor who supports the preparation of necessary documents and the flow of procedures.
Complete the procedures specified for each system (for the Tokyo subsidy, prior application) before proceeding with the construction!
For the Tokyo subsidy, after installation, you will need to submit a grant application and performance report, which will be reviewed before the grant is issued! (The flow of procedures varies by system)
▶ To “Subsidies and Grants that May Apply in Bunkyo Ward, Tokyo” within this article
Benefits of Introducing Solar Equipment
The benefits of introducing solar panels are as follows!
Benefit 1: Economic Benefits
The biggest advantage of introducing solar panels is the economic benefit!
The selling price of electricity has decreased compared to ten years ago, but by consuming the generated electricity, you can reduce the amount of electricity purchased from the utility company and gain benefits!
As electricity prices rise, the ability to cover your consumption with solar power becomes attractive!
If you plan to use the generated electricity at night, installing a storage battery is essential!
Furthermore, the selling price (FIT) for residential use (under 10kW) will be set at “24 yen/kWh for the first four years, and 8.3 yen/kWh from the fifth to the tenth year” for certifications after October 2025, and the same price will apply for the 2026 fiscal year. After the fifth year, it is likely to be more advantageous to use it in your home (self-consumption) rather than selling it, so combining it with a storage battery is also an option.
👉 Ministry of Economy, Trade and Industry | For purchase prices and periods, click here
Advantage 2 You can utilize subsidies!
The conditions and amounts of subsidies vary by prefecture and municipality, but if you meet the conditions, you may be able to utilize subsidies!
Reducing the actual burden through subsidies is a significant advantage!
In Bunkyo Ward, there is a possibility that the national, Tokyo Metropolitan, and Bunkyo Ward systems may apply. The subsidy in Bunkyo Ward is a post-application after installation, and the application period is determined based on the installation date (please check the reception status for each system).
Advantage 3 Environmentally friendly!
Solar power generation has low carbon dioxide emissions and can reduce dependence on fossil fuels, contributing to the mitigation of global warming.
Since solar panels themselves do not produce noise or exhaust gases during the generation process, they are considered an environmentally friendly method of power generation. (However, devices like power conditioners do have operational noise.)
Advantage 4 Heat insulation effects can be expected!!
By installing panels on the roof or rooftop, they block direct sunlight to the roof.
Especially in summer, this can help reduce the temperature of the roof, providing a heat insulation effect!
(Note that this does not improve the building’s insulation performance itself.)
Benefit 5 Electricity can be used even during power outages!!
If a storage battery is installed, it is possible to use electricity even during emergencies such as power outages!
Even without a storage battery, if you have a power conditioner with autonomous operation capability, you may be able to use electricity from a dedicated outlet during daytime generation.
(The devices, output, and duration that can be used during a power outage vary depending on the model and wiring method.)
What points should be noted when introducing solar power generation?
Next, we will explain the “three points to note” when installing solar panels!
Point 1 Maintenance costs can be incurred
A maintenance cost that is often overlooked is for the roof where solar panels are installed.
If you perform roof renovations 10 to 20 years later, there will be costs for removing and reinstalling the solar panels.
If the existing roof is deteriorated, it is reassuring to renovate it with durable roofing materials before installing solar panels!
Additionally, there will be costs for regular inspections of the equipment, repairs or replacements of the power conditioner, and updates due to the deterioration of the storage battery.
It would be reassuring to ask for a simulation considering maintenance costs before introducing solar panels!
Point 2 The risk of leaks increases depending on the roofing material
The fixing methods for slate roofs and tile roofs vary by construction method, but when fixing hardware to the roofing material or substrate with screws, waterproofing of the fixed parts is crucial.
In methods that involve making holes in the roof, the risk of leaks inevitably arises.
Of course, we will ensure proper waterproofing, but if you are concerned about making holes, replacing the roofing material with a metal roof and fixing the solar panels using the catch method is also an option. (The catch method has compatibility conditions between the roofing material and hardware, and it cannot be used with all metal roofs.)
Catch-type base hardware specifically for horizontal metal roofs
Point 3 The Roof Becomes Heavier
Installing solar panels will make the roof heavier. After investigating the existing roof, substrate, and load capacity, replacing with a lightweight roof may also be an option if necessary.
How to Choose Solar Panels?
There are many manufacturers of solar panels, and their output and costs vary.
It is not simply a matter of “this manufacturer has the best solar panels”; it is important to choose solar panels that are suitable for your life plan and building!
Here are some points to consider when comparing solar panels!
How to Choose 1: Compare Based on Total Output of the Roof
When installing solar panels on the roof, it is important to consider how much electricity can be generated in a limited area, and the more electricity generated, the better!
Solar panels come in various sizes and outputs depending on the manufacturer.
A 350W output panel and a 400W output panel may seem that the higher output panel is better at first glance.
However, if the size of the panels does not fit well on the roof, there may be cases where “20 panels of 350W can be installed” and “15 panels of 400W can be installed,” leading to different installation capacities on the same roof due to the size difference.
400W×15 panels = 6kW (total output of the roof)
350W×20 panels = 7kW (total output of the roof)
As shown above, even if the output of a single panel is lower, the total output of the roof may be higher!
It is important to consider the total output of the roof rather than the output of a single panel!
*The above is a calculation of total output (kW). The actual electricity generation (kWh) will vary depending on conditions such as roof orientation, slope, and shading.
How to Choose 2: Compare Based on Degradation Rate of Solar Panels
Solar panels have a degradation rate, and their output gradually decreases over 10 years and 20 years.
The degree of output reduction after long-term use varies by product. The manufacturer’s output guarantee value is a standard figure for warranty purposes and does not indicate the actual degradation rate or electricity generation itself.
By considering the degradation rate along with the initial output, you can choose solar panels without regrets!
How to Choose 3: Compare Based on Warranty Period
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty periods vary by manufacturer.
For output warranties, some manufacturers offer a 30-year warranty while others offer a 10-year warranty, so it varies!
Longer warranties are better, so be sure to check the warranty periods and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar Installation and Storage Battery Installation in Bunkyo, Tokyo
We have compiled frequently asked questions from customers considering the installation of solar panels and storage batteries in Bunkyo Ward, Tokyo. (Tap to reveal answers)
How much does it cost to install solar panels and storage batteries in Bunkyo Ward, Tokyo?
The cost varies depending on the installation capacity, equipment, and condition of the roof. In the above case study (solar panel 4.3kW + storage battery, completed in April 2025), it was 2.2 million yen to 2.3 million yen.
Guidelines for different capacities are available on our solar panel and storage battery installation pricing page. We will create a layout diagram based on the drawings and site survey and provide a free estimate!
Are there any subsidies available for solar and storage battery installation in Bunkyo Ward, Tokyo?
As of October 7, 2026, Tokyo’s “Household Solar Power Introduction Promotion Project” (for existing homes, 15万円 per kW for up to 3.75kW, maximum 450,000 yen) and “Household Storage Battery Introduction Promotion Project” (100,000 yen per kWh, maximum 1.2 million yen per household) are accepting pre-applications starting May 29, 2026, as listed on the official page of Tokyo (Cool Net Tokyo). Bunkyo Ward has a new energy and energy-saving equipment installation subsidy program (70,000 yen per kW for solar power systems, maximum 350,000 yen; 20,000 yen per kWh for home storage systems, maximum 100,000 yen) that can be applied for after installation within the application period corresponding to the installation date, as stated on Bunkyo Ward’s official page. The national DR home storage battery project has closed its public recruitment.
Since the application status may change, please check the subsidy and grant section and consult with us before signing a contract.
Can I apply for subsidies after the construction is completed?
This depends on the system. Tokyo’s subsidies require pre-application, while Bunkyo Ward’s grants are a post-application system that allows you to apply after installation. Conditions such as whether you can contract and start construction before applying vary by system, so please confirm before signing a contract.
The order of procedures varies by system, so please check before signing a contract or starting construction.
Can solar panels be installed on a slate roof? I’m worried about leaks.
It is possible to install on a slate roof, but it is necessary to check the condition of the roofing material and substrate. The fixing method varies by construction method, and if the method involves fixing brackets to the roofing material or substrate, waterproofing treatment of the fixed parts is essential.
Kakeru Koumuten is a specialized exterior renovation company strong in roofing work, so we will check the condition of the roof before installation and suggest methods such as roof overlay or replacement if deterioration is advanced.
My roof is old. Should I do a roof renovation first?
This depends on the condition of the roof. If a roof renovation is needed 10 to 20 years after installation, the cost of removing and reattaching the solar panels will be incurred separately. If the remaining lifespan of the roof is short, it may be more cost-effective to renovate to a highly durable roofing material before installation.
Please consult us on how to proceed with the installation after checking the condition of the roof during the site survey!
Is it better to install a storage battery together with solar panels?
For those who want to use generated electricity at night or prepare for power outages, simultaneous installation is recommended. The selling price will be 8.3 yen/kWh after the fifth year, making it more advantageous to use it at home rather than selling it.
Additionally, the Tokyo Metropolitan Government’s subsidy for storage batteries (for the Reiwa 8 fiscal year, it is 100,000 yen per kWh, with a maximum of 1,200,000 yen per household) aims to increase self-consumption of electricity generated by solar power. In Bunkyo Ward, household storage systems designated by SII that connect to solar power generation or Enefarm are included in the subsidy. You can compare “solar power only” and “solar power + storage battery” through a financial simulation.
How many kW can be installed on my roof? Is it okay for north-facing roofs or roofs with shadows?
The capacity that can be installed varies depending on the shape, orientation, and size of the roof. At Kakeru Koumuten, we create a layout diagram from the drawings and on-site survey, and we will provide you with the installation capacity and power generation simulation.
Bunkyo Ward is located on the eastern edge of the Musashino Plateau, with lowlands along the plateau and the Kanda River, as well as hilly areas in between. The shape and orientation of the roof, the way shadows are cast by surrounding buildings, and the capacity that can be installed differ from house to house. You can check the expected power generation through the power generation simulation.
How long does the construction period take?
In the above construction example (solar panel 4.3 kW + storage battery), it took about 3 days. The duration may vary depending on whether roof work is done simultaneously and the shape and installation capacity of the roof.
Additionally, there will be a separate period required for applying for subsidies and to the power company, so please consult us as soon as possible.
What is the current selling price (FIT)?
For residential use (under 10 kW), from the certifications after October 2025, the first four years will be 24 yen/kWh, and from the fifth to the tenth year, it will be 8.3 yen/kWh, with the same price applied in the 2026 fiscal year.
The idea is to recover initial costs more quickly in the first four years and then focus on self-consumption. Kakeru Koumuten provides a financial simulation that takes into account loan interest rates and electricity costs.
Can you handle maintenance and inspections after installation?
Yes, we can. Kakeru Koumuten sends out annual after-maintenance notices via DM and visits customers who wish to have inspections. We can also clean solar panels using a special brush if the power generation decreases due to dirt.
Since it is difficult to check areas on the roof by yourself, please feel free to consult us if you have any concerns.
Can you also handle renovations for roofs that already have solar panels installed?
Yes, we can. Kakeru Koumuten can detach and reattach solar panels in-house, allowing us to remove the panels, perform roof overlay (cover method) or re-roofing, and then reinstall them all in one go. The removed panels can be stored in our own warehouse.
For costs, please refer to the solar panel removal and hot water heater removal pricing page.
If you are looking for a solar panel installation company in Bunkyo, Tokyo, please consult Kakeru Koumuten.
Our company handles a wide range of exterior renovations, including solar panels, roof work, and exterior wall work in Bunkyo, Tokyo.
We have received requests from many customers, including renovation companies and real estate agencies, who have contacted us!
Kakeru Koumuten promises “high-quality renovations at low cost”, and we have received positive feedback from numerous customers.
We continue to update our construction achievements every year, and we will strive to improve quality to satisfy even more customers in the future.
Our company is capable of performing all exterior renovations, including roof overlay work, roof replacement work, partial roof repairs, exterior painting, and exterior wall cover methods, all by our own team.
We are also happy to handle small jobs such as partial repairs and rain gutter cleaning!
In urgent cases such as leak repairs, we may be able to provide temporary measures without setting up scaffolding, as long as safety can be ensured, so please consult with us!
“I want to know about recommended solar panels”, “I want to keep costs as low as possible”, “I just want an estimate for now”, we will provide the best solutions for your specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s shoes and will propose the best construction plan!
We are confident that we will not be outdone in terms of cost, quality, and planning compared to other companies in exterior work!
We are confident, so we welcome competitive quotes!
Estimates are completely free, and if our company is inferior to others, you are free to decline!
Characteristics of Bunkyo, Tokyo and Points for Solar Work
Bunkyo Ward is located on the eastern edge of the Musashino Plateau, consisting of lowlands created by steep slopes, cliffs, and rivers such as the Kanda River and the Senkawa and Aizome Rivers. It is divided into five plateaus: Sekiguchi, Kohinata, Koishikawa, Hakusan, and Hongo, with valleys between the plateaus. Below are summarized the characteristics of the terrain in Bunkyo, Tokyo, and points to consider when installing solar panels and storage batteries. (Tap to open)
View the characteristics of Bunkyo, Tokyo and points for solar work
■ A terrain with plateaus, slopes, and lowlands. Check scaffolding and delivery routes for each site.
In areas with many slopes and cliffs, there are often residences with elevation differences, narrow front roads, or facing slopes. In such sites, the way scaffolding is set up and the delivery routes for panels and storage batteries will change. At Kakeru Koumuten, our own scaffolding team plans the scaffolding according to the site, creates layout diagrams from the drawings and on-site surveys, and you can confirm this with a power generation simulation.
■ Check the flood, storm surge, and internal water hazard maps. Pay attention to the installation location of equipment
The flood hazard map for Bunkyo Ward assumes flooding from the Kanda River and Arakawa River, while the storm surge hazard map targets the Tokyo Bay coastline, and the internal water hazard map is published separately. Depending on where you install the power conditioner and storage battery, whether indoors or outdoors, the impact during water damage may vary. Please check the assumptions for your residence on the ward’s hazard map and consult with us regarding the installation location and height, in accordance with the manufacturer’s installation conditions.
■ Roof types and ages vary from house to house. Check the roof and waterproofing before installation
Even within the same ward, the types of roofs, ages, and shapes of the land vary from house to house. The subsidies in Bunkyo Ward also apply to management associations for solar power generation systems, and the shape of the roof and the capacity that can be installed differ depending on the type of building. At Kakeru Koumuten Co., Ltd., we will check the type and condition of the roof and the situation of the land before installation and propose methods for securing, waterproofing arrangements, and scaffolding plans.
■ The annual sunshine hours at the Tokyo Observatory is about 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), the annual sunshine hours at the Tokyo Observatory is about 1,927 hours, with January (about 193 hours) having the most and June during the rainy season (about 124 hours) having the least. (This is a reference value, not an observation value within Bunkyo Ward.)
The power generation in Bunkyo Ward can also be affected by the shadows of surrounding buildings and the elevation differences of hills and plateaus, so conducting an annual power generation simulation and selecting the capacity of the storage battery to match the times of high electricity usage are key points.
Our company handles many exterior construction and solar power projects in Bunkyo Ward, Tokyo.
We are happy to assist with partial roof repairs such as roof overlay work, roof replacement, and leak repairs, as well as other repairs! Please feel free to consult us about any sudden troubles!
Service Area in Bunkyo Ward, Tokyo
Kakeru Koumuten Co., Ltd. accepts requests throughout Kanagawa Prefecture and all of Tokyo.
List of Areas in Bunkyo Ward, Tokyo
Otsuka, Bunkyo Ward / Otowa, Bunkyo Ward / Kasuga, Bunkyo Ward / Koishikawa, Bunkyo Ward / Korakuen, Bunkyo Ward / Kohinata, Bunkyo Ward / Suidō, Bunkyo Ward / Sekiguchi, Bunkyo Ward / Sengoku, Bunkyo Ward / Sendagi, Bunkyo Ward / Nishikata, Bunkyo Ward / Nezu, Bunkyo Ward / Hakusan, Bunkyo Ward / Honkomagome, Bunkyo Ward / Hongo, Bunkyo Ward / Mukogaoka, Bunkyo Ward / Mejirodai, Bunkyo Ward / Yayoichi, Bunkyo Ward / Yushima, Bunkyo Ward
・Leave your exterior wall painting in Bunkyo, Tokyo to Kakeru Koumuten!
・Leave your roof renovation in Bunkyo, Tokyo to Kakeru Koumuten!
・Leave your exterior renovation in Bunkyo, Tokyo to Kakeru Koumuten!
・Kakeru Koumuten Co., Ltd. construction achievements
・Kakeru Koumuten Co., Ltd. after maintenance
・Kakeru Koumuten Co., Ltd. construction menu and price list
・Kakeru Koumuten Co., Ltd. staff blog and announcements
・Explaining the importance of comparative estimates and points to consider!
・Top 12 solar power generation manufacturers! Features and selection points also introduced!
・What are the installation costs for solar power generation? Thorough explanation of tips to reduce costs!
・What are the best locations for installing solar power generation? Points for selecting installation locations also introduced!
・Here is the introduction to solar power generation estimates!
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contact Kakeru Koumuten Co., Ltd.
Kakeru Koumuten is a young company whose team is, on average, in their late twenties, but our skills are second to none.
Our greatest strength is that we handle scaffolding, roofing and painting entirely in-house. In an industry where these tasks are usually divided among contractors, our complete service simplifies project management and helps keep costs down. Above all, if a problem arises, we respond promptly.
We proudly describe ourselves as the youngest and most helpful renovation company in Kanagawa!
