Leave Your Solar Panel Installation Work in Toshima, Tokyo to Kakeru Koumuten Co., Ltd.!
For Solar Panel and Battery Installation in
Toshima, Tokyo,
trust Kakeru Koumuten!
Kakeru Koumuten is a specialized exterior renovation company headquartered in Aoba Ward, Yokohama City.
As a company strong in roofing work, we are entrusted withsolar panel and battery installation considering roofing and waterproofing!
“How to Choose a Solar Panel Contractor in Toshima”
“Costs for Solar Panel and Battery Installation”
“Subsidies Available for Solar System Installation in Toshima”
We will also explain the above three points!
Installing solar panels has risks, such as“the occurrence of leaks” and other troubles.
To ensure a satisfactory solar panel installation, we recommend obtainingcomparative estimates from about three companies!
Table of Contents (Tap to Open/Close)
- Reasons Kakeru Koumuten is Chosen for Solar Panel Installation in Toshima, Tokyo
- Roof Inspection Before Installing Solar Panels
- Possible Subsidies and Grants Available in Toshima
- 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 Installation Company in Toshima, 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 Toshima
- If You’re Looking for a Solar Panel Installation Company in Toshima, Contact Kakeru Koumuten
- Characteristics of Toshima, Tokyo and Key Points for Solar Installation
- Service Areas in Toshima, Tokyo
Reasons Kakeru Koumuten is Chosen for Solar Panel Installation in Toshima, Tokyo
The reasons why our company is entrusted with solar panel installation by customers in Toshima, Tokyo include
one reason being that “Kakeru Koumuten serves Kanagawa and Tokyo areas”,
and we have “unique strengths in solar panel installation that cannot be imitated by other companies”, which has 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 multiple estimates!
1. We Can Also Handle Exterior Renovations Other Than 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 you are knowledgeable about solar panels, there may be cases where the roof and waterproofing at the installation site are outside your expertise, so caution is necessary.
It’s reassuring to have someone knowledgeable about the roof 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 prepared the following warehouses and material storage areas to provide low-cost, high-quality solar work and exterior renovations.
We have established five bases centered around Yokohama City, Kanagawa Prefecture for material storage and showrooms.
In-house Scaffolding Materials
To ensure safety during work on the roof, we own the scaffolding materials necessary for temporary scaffolding according to the construction conditions and can assemble the scaffolding in-house.
By not outsourcing scaffolding work and using our own scaffolding team, we can also cut costs for scaffolding work.
We have scaffolding materials for approximately 50 single-family homes!
Even in the urban area of Toshima Ward, our in-house scaffolding team will plan the scaffolding according to the site.
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 can purchase materials at a lower cost!
Additionally, we always have a stock of roofing materials, so we can respond 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 we hold meetings, but you can also
check the actual foundation brackets for solar panels and see how they are installed on roofing materials!
We can also provide simulations for potential earnings and installation costs when introducing solar panels!
Since roofing and exterior wall work often accompany each other, we also have 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 offer 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 throughout the process, communication can proceed smoothly.
We can provide consistent in-house construction from temporary scaffolding installation, exterior wall painting, to roof renovations!
4. Various Permits Obtained & Skilled Workers Available
We have obtained permits for construction work and industrial waste collection and transportation!
We also have nationally certified sheet metal workers and painting specialists, giving us confidence in our construction techniques.
We are capable of handling large-scale roof projects for factories and other facilities!
5. Warranty and Aftercare Maintenance
In addition to the manufacturer’s warranty, solar panel installation work comes with 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 coverage and conditions vary based on the warranty details.)
Aftercare maintenance is available annually, and we send out notification DM every 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 altitudes, we can utilize drones to assist!
During leak investigations, we can also conduct inspections using a thermal imaging camera.
If the power generation of your solar panels decreases due to dirt or other factors, we can also provide cleaning services using specialized brushes.
We will respond according to your preferences.
7. Human Resource Development
To improve 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 to ensure that each staff member can handle various cases.
8. Creation of Easy-to-Understand Materials and Simulations
Kakeru Koumuten provides not only “estimates,” “layout diagrams,” and “power generation simulations” but also a “solar installation 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.
We compile easy-to-understand materials that include points to consider and disadvantages for customers who may not be familiar with solar installations!
We encourage you to obtain comparative estimates and compare them with other companies’ plans!
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 okay 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 compiled 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 materials is short, we may suggest a roof renovation first. |
| 2. Condition of the Substrate and Waterproof Sheet | If the sheathing boards or roofing (waterproof sheet) under the roofing materials 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 amount of electricity generated. We can 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 size of the panels, we will compare based on the total output of the roof. |
| 5. Fixing Method and Waterproofing Details | We will check whether the method involves making holes in the roofing materials for fastening or using brackets to secure the roofing materials. 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 added. 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 locations 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. |
Fixing Methods and Checkpoints by Roofing Material
| Roof Material | Main Fixing Method | Pre-Installation Check Points |
|---|---|---|
| Slate Roof | Varies by method (e.g., fixing brackets with screws to the roof material and substrate) | Waterproofing of fixed 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 secure 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 renovate the roof 10 to 20 years after installation, there will be additional costs for the removal and reinstallation of solar panels. If the roof is deteriorating, renovating to a highly durable roofing material before installation may help reduce costs in the long run.
Kakeru Koumuten Co., Ltd. specializes in roofing work and can also handle the removal and reinstallation of solar panels, so please consult us according to the condition of your roof!
▶ Click here for roof renovations in Toshima, Tokyo
Subsidies and Grants Available inToshima, Tokyo
If you are introducing solar panels or storage batteries in Toshima, Tokyo, there is a possibility that you may be eligible for programs from the “National Government,” “Tokyo Metropolitan Government,” and “Toshima City”.
The following information is based on the official pages of each program as of October 7, 2026. The application status may change depending on the budget and recruitment period, so please check the latest information before contracting or starting work.
Eligibility Conditions and Application Timing for Subsidy Programs
| Program | Main Eligibility Conditions | Subsidy Amount | Application Period & Status |
|---|---|---|---|
| Tokyo Metropolitan Government “Reiwa 8 Year Household Solar Power Generation Promotion Project” (Cool Net Tokyo) | New installation of certified solar modules in residential properties or their premises in Tokyo, with a system capacity of less than 50kW. Pre-application before installation is required. | Existing homes: 150,000 JPY/kW for up to 3.75kW (maximum 450,000 JPY), 120,000 JPY/kW for over 3.75kW New homes: 120,000 JPY/kW for up to 3.6kW (maximum 360,000 JPY), 100,000 JPY/kW for over 3.6kW (Additional costs for mounting frames, waterproofing work, and renovation defect insurance, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 to March 30, 2029 |
| Tokyo Metropolitan Government “Reiwa 8 Year Household Storage Battery Promotion Project” (Cool Net Tokyo) | New installation of storage batteries in residential properties in Tokyo, with SII registered equipment. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries alone. Pre-applications after October 1, 2026 will only be eligible for SII registered products for Reiwa 8. | Storage battery package: 100,000 JPY/kWh (maximum 1,200,000 JPY per household) Storage battery unit expansion: 60,000 JPY/kWh (maximum 720,000 JPY per household) (Additional incentives for participation in DR demonstrations, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 |
| Toshima Ward “Eco Housing Promotion Subsidy” Reiwa 8 Year | Residents with a registered address in the ward who purchase and install equipment for their own residence (consent from the owner is required for rental properties). Only unused items are eligible; used items and leases are not eligible. Solar power generation must be certified by JET or similar, and storage systems must be registered as eligible equipment with SII. No application before construction is required, and applications are made after completion of work. | Solar power generation: 20,000 JPY per kW (maximum 80,000 JPY) Storage systems: 10,000 JPY per kWh (maximum 50,000 JPY) |
Application acceptance: From May 25, 2026 to March 1, 2027 (must arrive by this date) Construction completion period: From February 1, 2026 to January 31, 2027 Applications will be accepted on a first-come, first-served basis, and will close once the budget is exceeded. As of October 5, 2026, the planned grant amount against the budget is reported to be 52% on the ward’s official page. |
| National “DR Household Storage Battery Project” (Reiwa 7 Year Supplement) | New installation of 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 3/10; maximum 600,000 JPY per application). | The budget was reached on May 29, 2026, and the public recruitment has ended (applications are currently not possible). |
| National “Mirai Eco Housing 2026 Project” (Renovation) | The storage battery is one of the eligible facilities, but it must be combined with essential construction work such as insulation renovation of windows (openings) and the building structure; installation of the storage battery alone cannot be applied for. Solar panels are not included as eligible facilities | Storage Battery: 96,000 JPY/unit | Ends as soon as the budget limit is reached. Please check the official website for application status |
In Tokyo, a pre-application before installation is required for the subsidy, and starting construction beforehand may result in ineligibility. In Toshima Ward, pre-application before construction is not necessary, and you will apply after the completion of construction, but you must meet the requirements for eligible equipment, completion period, and necessary documents (completion certificate, receipts, etc.), and applying does not guarantee that the subsidy will be granted. The Toshima Ward subsidy is on a first-come, first-served basis, and applications will close once the budget is reached. If the national government and Tokyo do not prohibit simultaneous applications, they can be combined. Procedures differ by system, so please confirm before contracting and starting work.
Kakeru Koumuten Co., Ltd. will guide you on the eligibility conditions for each system after confirming them.
Tokyo “Reiwa 8 Year Household Solar Power Generation Promotion Project”
Tokyo is providing subsidies for those installing solar power generation systems in residential homes through Cool Net Tokyo. The target is systems using certified solar modules installed newly in residential homes or on their premises, with a capacity of less than 50kW. A pre-application before installation is required.
The subsidy amount for existing homes is 150,000 JPY/kW for 3.75kW or less (maximum 450,000 JPY), and 120,000 JPY/kW for more than 3.75kW. Additionally, there are extra items such as installation of mounting frames, waterproofing work, and renovation defect insurance. The pre-application period is from May 29, 2026, and the application for grants and performance reports is from June 30, 2026, to March 30, 2029. For details on eligible equipment and conditions, and budget status, please check the official page.
👉 Cool Net Tokyo | Official page for solar power generation
Tokyo “Reiwa 8 Year Household Storage Battery Promotion Project”
Tokyo is also providing subsidies for newly installed storage batteries in residential homes. The subsidy amount is 100,000 JPY per kWh for storage battery packages (maximum 1,200,000 JPY/unit), and 60,000 JPY per kWh for additional storage battery units (maximum 720,000 JPY/unit), with additional amounts for participation in DR demonstrations.
The target is equipment registered with SII (Environmental Collaboration Initiative). If you apply for pre-application after October 1, 2026, only equipment listed in the Reiwa 8 Year SII registered product list will be eligible. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries alone. The application for grants and performance reports has been open since June 30, 2026.
👉 Cool Net Tokyo | Official page for storage batteries
Toshima Ward “Eco Housing Promotion Subsidy”
In Toshima Ward, a subsidy program called “Eco Housing Promotion Cost Subsidy” is being implemented for those who install environmentally friendly equipment in residential homes within the ward. For the fiscal year Reiwa 8, the subsidy amounts are 20,000 yen per 1 kW output for solar power generation systems (up to 80,000 yen), and 10,000 yen per 1 kWh storage capacity for storage systems (up to 50,000 yen). Eligible applicants must have a registered address within the ward and must purchase and install the equipment for their own residence; for rental properties, the owner’s consent is required. Only unused items are eligible; used items and leases are not covered.
Solar power generation systems must be certified by a JET or IECEE-PV-FCS accredited organization, while storage systems must be registered as eligible equipment by SII (Environmental Collaboration Initiative). No application is required before construction; applications are made after completion (applications will be accepted from May 25, 2026, to March 1, 2027, for equipment completed between February 1, 2026, and January 31, 2027). Applications are processed on a first-come, first-served basis, and will end once the budget is exceeded. As of October 5, 2026, the official page of the ward states that the planned grant amount is 52% of the budget. If not prohibited by the national or Tokyo Metropolitan Government, it can be combined with other subsidies.
👉 Click here for the official Toshima Ward page (Eco Housing Promotion Cost Subsidy)
National Subsidy “DR Home Storage Battery Project (Support Project for Home Storage System Introduction 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 individuals who are newly introducing registered storage systems that can be utilized for demand response (DR), and for the fiscal year Reiwa 7 supplementary budget, the subsidy amount was based on a standard of 34,500 yen per 1 kWh initial effective capacity, with a subsidy rate of up to 30% and a maximum of 600,000 yen per application. There are conditions such as that contracts or orders made before the grant decision are not eligible.
However, the Reiwa 7 supplementary budget reached its application budget on May 29, 2026, and the public offering has ended (the previous fiscal year’s Reiwa 6 supplementary budget also ended on July 2, 2025). Applications are currently not being accepted, so please check the official site 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 site of the DR Home Storage Battery Project
Solar Panel Installation & Storage Battery Installation Price List
⇧Service Menu | For Costs of Solar Panel Installation and Battery Installation, Click Here
⇧Service Menu | For Costs of Solar Panel Removal and Water Heater Removal, Click Here
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and batteries should be checked separately as “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 (kilowatts). Battery capacity is compared in kWh (kilowatt-hours), which represents the amount of electricity that can be stored.
The amount of kW that can be installed on a roof varies for each house based on the roof’s shape, orientation, and size. 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 costs as approximately 800,000 yen to 1,200,000 yen for 3-5 kW and 1,200,000 yen to 1,900,000 yen for 6-10 kW. (These are just approximate amounts and can vary based on wiring length, scaffolding range, existing roofing materials, panel layout, etc.)
▶ Service Menu | For Costs of Solar Panel Installation and Battery Installation, Click Here
Items to Confirm in the Estimate (Cost Confirmation)
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, total installation capacity (kW) are listed. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, installation location (indoor/outdoor). Also confirm if it is a type that controls the battery together. |
| 3. Storage Battery | Manufacturer, model number, capacity (kWh), range usable during a power outage (whole house or specific circuits), installation location. |
| 4. Mounting Frame and Fittings | Name of fittings suitable for the roofing material and method of securing (whether it uses drilling or clamping). |
| 5. Wiring and Electrical Work | Wiring route and length, work around the distribution board, presence of a monitor to check power generation. |
| 6. Roof Reinforcement and Waterproofing | Details of waterproofing treatment at the fixing points, whether necessary roof repairs and substrate reinforcements are included. |
| 7. Applications | How much support is included for applications to the power company, certification 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 and old panels, as well as disposal costs for waste materials, are included. |
| 10. Tax Classification and Warranty | Whether prices are tax-inclusive or tax-exclusive, conditions under which additional costs may arise, details and duration of manufacturer and workmanship warranties. |
If the capacities differ, both the price and power generation will change. Kakeru Koumuten Co., Ltd. welcome comparisons, so if you bring estimates from other companies, we can explain the differences item by item!
Self-Estimate and Financial Simulation for Solar Power Generation
With the simulator above,
you can obtain a rough estimate 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 a rough estimate and financial simulation!
*The simulation results are approximate. Actual finances may vary based on assumptions such as electricity rates, self-consumption ratios, selling prices, and costs for equipment inspection or replacement.
Customer Testimonials
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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 class |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Arrangement |
| Fixed using catch type hardware to grip the horizontal metal roof (Catch Method) |
| Price Range |
| 2,200,000 JPY～2,300,000 JPY *Due to the subsidy being granted, the actual burden amount is approximately 1,000,000 JPY Expected recovery period for construction costs: about 8 to 9 years (self-consumption) *The subsidy 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 subsidies are available, and I would like to know how much can be granted. |
Our Proposal
We visited to provide a quote and created a layout diagram for the solar panels from the drawings!
The layout diagram shows the arrangement of solar panels 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 subsidies that will be granted, and we explained this to the customer along with the estimate!
How to Choose a Solar Panel Installation Contractor in Toshima, Tokyo
There are many solar panel installation contractors available in Toshima, Tokyo, and you may be unsure which contractor to choose.
Therefore, when requesting solar panel installation and battery storage installation work, let’s check the following 4 points.
● Have extensive knowledge not only about solar panels but also about roofs
● Confirm the existence of warranties and aftercare maintenance
● Obtain estimates from multiple contractors (3 companies as a guideline)
● Check if they provide support for subsidy applications
By confirming the above 4 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 at the installation site of the solar panels is also crucial.
⚠︎Examples of troubles caused by insufficient verification of roofs and waterproofing
・Solar panels were installed on a severely deteriorated roof, resulting in leaks
・Solar panels were installed on a roof with a short lifespan, necessitating a renovation to detach and reattach the solar panels 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 for installation that avoids unnecessary expenses and unexpected troubles.
▶ Go to “Roof Verification Before Installing Solar Panels” in this article
Confirm the existence of warranties and aftercare maintenance
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 a manufacturer’s warranty, also 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 be able to respond under the warranty, provided it is within the warranty period and conditions.
Additionally, some contractors offer after-sales service separate from warranties, so be sure to check if the contractor you are considering has after-sales service.
Changes or damage on the roof can occur in areas that are not visible, so there is a possibility that customers may not notice them themselves.
By conducting inspections during after-sales maintenance, we can detect abnormalities early, making it easier to prevent major repairs or failures!
Kakeru Koumuten Co., Ltd. provides a leak warranty as part of the workmanship warranty for solar panel installations. (The warranty for solar panel installations is 10 years, and depending on the condition of the roof before installation, we may not be able to provide a warranty without performing roof renovations.)
We also conduct after-sales maintenance and send out annual DM!
Please check the DM, and if you wish, we will visit you for after-sales maintenance!
Obtain estimates from multiple contractors (3 companies as a guideline)
When requesting the installation of solar panels, be sure to 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 services from your preferred contractor at a lower price, we recommend obtaining estimates from multiple contractors.
When comparing estimates, please check the following:
“Check the items in the estimate”
“Type of solar panels”
“Warranties and after-sales services”
Make sure to compare these details carefully! If the quality of the auxiliary materials is low or if steps are skipped, costs can be reduced, so avoid making judgments based solely on price!
▶ Go to “Breakdown of Installation Capacity, Equipment, and Construction Costs” in this article
Check if they provide support for subsidy applications
There may be subsidies available for solar panel installations and battery installations, but if the order of procedures is incorrect or if there are deficiencies in the documents, the subsidy may not be granted.
Some systems require personal applications and cannot be handled by the contractor, and some require pre-application before installation, so it is reassuring to have a contractor that supports the preparation of necessary documents and the flow of procedures.
Complete the procedures specified for each system (for Tokyo’s subsidies, pre-application before installation) before proceeding with the construction! In Toshima Ward, pre-application for subsidies is not required, and applications are made after the completion of the work!
In the case of subsidies in Tokyo, the process involves submitting a grant application and performance report after the completion of the work, which will be granted after review! For the grants in Toshima Ward, applications are made after the completion of the work, and they will be granted after review! (The procedure may vary depending on the system)
▶ Go to “Subsidies and Grants that May Be Applicable in Toshima Ward” within this article
Benefits of Introducing Solar Power Equipment
The benefits of introducing solar panels are summarized in the following five points!
Benefit 1: Economic Advantage
The biggest advantage of introducing solar panels is the economic benefit!
Although the selling price of electricity has decreased compared to ten years ago, you can gain benefits by reducing the electricity you buy from power companies by consuming the electricity you generate!
As electricity prices rise, the appeal of being able to cover your consumption with solar power increases!
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 in the 2026 fiscal year. After the fifth year, it is generally more advantageous to use it at home (self-consumption), making the combination with a storage battery a viable option.
👉 For purchase prices and periods, click here
Benefit 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 amount through subsidies is a significant advantage!
In the case of Toshima Ward, in addition to national and Tokyo metropolitan programs, you may be eligible for the Toshima Ward Eco Housing Promotion Subsidy (for solar power systems and storage systems) (the ward’s subsidy is applied for after the completion of the work and is on a first-come, first-served basis).
Benefit 3 Environmentally Friendly!
Solar power generation contributes to the reduction of carbon dioxide emissions and dependence on fossil fuels, helping to mitigate global warming.
Since solar panels themselves do not produce noise or exhaust gases during the power generation process, they are considered an environmentally friendly method of generating electricity. (Devices like power conditioners may produce operational noise)
Advantage 4 Heat insulation effect is expected!!
By installing them on the roof or rooftop, the panels block direct sunlight from hitting the roof.
Especially in summer, they can help reduce the temperature rise of the roof, providing an expected heat insulation effect!
(This does not improve the building’s insulation performance itself)
Advantage 5 Electricity can be used even during power outages!!
If a storage battery is installed, it is possible to use electricity even during emergencies like 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 particularly overlooked maintenance cost 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 consider maintenance costs in simulations before introducing solar panels!
Point 2 The risk of leaks may increase depending on the roofing material
The methods for securing slate roofs and tile roofs vary depending on the construction method, but when using screws or other fasteners to secure the roofing materials and substrate, waterproofing treatment at the fastening points becomes crucial.
In methods that involve making holes in the roof, there is inevitably a risk of leaks.
Of course, we will ensure thorough waterproofing treatment, but if you are concerned about making holes, one option is to replace the roofing material with a metal roof and secure the solar panels using the catch method. (The catch method has compatibility conditions between the roofing material and the fasteners, and it cannot be used with all metal roofs.)
Catch-type base fasteners for horizontal metal roofs
Note 3: The roof will become heavier
To install solar panels, the roof will become heavier. After investigating the existing roof, substrate, and load-bearing capacity, replacing it with a lighter 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 widely.
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!
Choosing Method 1: Compare based on the total output of the roof
When installing solar panels on the roof, it is important to consider how much power can be generated in the limited area, and the more power generated, the better!
Solar panels come in various sizes and outputs depending on the manufacturer.
For example, 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 panel does not fit well with the roof, “20 panels of 350W can be installed, while only 15 panels of 400W can be installed,” which means the number of panels that can be installed may differ even 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 calculations are for total output (kW). The actual power generation (kWh) will vary depending on conditions such as the roof’s orientation, slope, and shading.
Choosing Method 2: Compare based on the degradation rate of solar panels
Solar panels have a degradation rate, and their output gradually decreases over 10 and 20 years.
The degree of output reduction after long-term use varies by product. The manufacturer’s output warranty values are standard figures for guarantees and do not indicate the actual degradation rate or power generation itself.
Choosing solar panels while considering both initial output and degradation rates will lead to a decision without regrets!
How to Choose 3: Compare by Warranty Period
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty periods differ by manufacturer.
Some manufacturers offer a 30-year warranty for output, while others provide only a 10-year warranty, so it varies widely!
A longer warranty is always better, so be sure to check the warranty period and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar and Battery Installation in Toshima Ward
We have compiled frequently asked questions from customers considering the installation of solar panels and batteries in Toshima Ward. (Tap to open the answers)
How much does it cost to install solar panels and batteries in Toshima Ward, Tokyo?
The cost varies depending on the installation capacity, equipment, and roof condition. In the above construction example (solar panel 4.3kW + battery, completed in April 2025), it was 2.2 million yen to 2.3 million yen.
Guidelines by capacity are available on the solar panel and battery installation pricing page. We will create a layout diagram from the drawings and site survey and provide a free estimate!
Are there any subsidies available for solar and battery installation in Toshima Ward?
As of October 7, 2026, Tokyo’s subsidies for solar power generation and batteries (Cool Net Tokyo) are accepting pre-applications. For batteries, only SII registered devices (registered products for Reiwa 8) from pre-applications after October 1, 2026, are eligible. The Toshima Ward Eco-Housing Promotion Subsidy (20,000 yen per kW for solar power, maximum 80,000 yen; 10,000 yen per kWh for battery systems, maximum 50,000 yen) is accepting applications until March 1, 2027, and the official page of the ward states that as of October 5, 2026, the scheduled grant amount ratio against the budget is 52% (first-come, first-served, and will end when the budget is reached). The national DR home battery project has ended its public recruitment.
Since the application status may change, please refer to the subsidy and grant section and consult with us before signing a contract.
Can I apply for subsidies after the construction is completed?
For many programs, procedures are required before construction. Tokyo’s subsidies require pre-application before installation, and if you install first, you will be ineligible. On the other hand, Toshima Ward’s grants do not require pre-application and can be applied for after completion of construction. Procedures differ by program.
Since the order of procedures varies by program, please confirm before signing a contract or starting construction.
Can solar panels be installed on slate roofs? 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 beforehand. The fixing method varies depending on the method used, and when fixing hardware to the roofing material or substrate, waterproofing treatment of the fixed parts is essential.
Kakeru Koumuten Co., Ltd. is a specialist in exterior renovations with a strong focus on roofing work, so we will check the condition of the roof before installation and suggest methods such as roof overlay (cover method) or re-roofing if deterioration is advanced.
My roof is old. Should I do a roof renovation first?
It depends on the condition of the roof. If a roof renovation is needed 10 to 20 years after installation, the cost of removing and reinstalling 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 through a site survey!
Should I install a storage battery together with the solar panels?
If you want to use the generated electricity at night or prepare for power outages, simultaneous installation is recommended. The selling price for electricity will be 8.3 yen/kWh after the fifth year, making it more beneficial to use it in your home rather than selling it.
Additionally, the Tokyo Metropolitan Government’s subsidy for storage batteries is designed for simultaneous installation with solar panels, but you can also apply for the subsidy for storage batteries alone. You can compare “solar panels only” and “solar panels + 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 Co., Ltd., we create a layout diagram based on the drawings and site survey, and provide you with the installation capacity and power generation simulation.
Even in the urban area of Toshima Ward, the way shadows are cast by surrounding buildings varies from house to house. You can check the expected power generation through the power generation simulation.
How long will the construction period be?
In the above construction example (solar panel 4.3 kW + storage battery), it took about 3 days. The duration may vary depending on whether roofing work is performed simultaneously and the shape and installation capacity of the roof.
Please note that additional time is required for applications for subsidies and power companies, so please consult us as soon as possible.
What is the current selling price (FIT)?
For residential use (less than 10 kW), the selling price for certifications after October 2025 will be 24 yen/kWh for the first 4 years, and 8.3 yen/kWh from the 5th to the 10th year, and the same price will apply in the 2026 fiscal year.
The idea is to recover the initial costs quickly in the first 4 years and then focus on self-consumption. Kakeru Koumuten Co., Ltd. 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 Co., Ltd. sends out annual after-maintenance notices via DM and visits customers who wish to have inspections. We can also provide cleaning of solar panels using a specialized brush if the power generation is reduced due to dirt.
The roof is a place that is difficult to check by yourself, so if you have any concerns, please feel free to consult us.
Can you also handle renovations for roofs that already have solar panels installed?
Yes, we can. Kakeru Koumuten Co., Ltd. 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 consistently. The removed panels can be stored in our own warehouse.
For costs, please refer to the solar panel detachment and water heater removal pricing page.
If you are looking for a solar panel installation contractor in Toshima Ward, please consult Kakeru Koumuten
Our company handles a wide range of exterior renovations, including solar panels, roof work, and exterior wall work in Toshima Ward, 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 many customers.
We continue to update our construction performance every year, and we will strive to improve quality to satisfy even more customers in the future.
Our company can perform not only roof overlay work and re-roofing but also partial roof repairs, exterior painting, and exterior wall cover methods, all with our own team.
We are 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 emergency measures without setting up scaffolding, as long as safety can be ensured, so please consult us!
“I want to know recommended solar panels”, “I want to keep costs down as much as possible”, “I just want an estimate for now”, we will provide optimal solutions for your specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s position and propose the best construction plans!
We are confident that we will not be outdone in terms of cost, quality, and organization compared to other companies in exterior construction!
We welcome competitive quotes because we are confident!
Estimates are completely free, and if our company is found to be inferior to others, you are free to decline!
Characteristics of Toshima Ward, Tokyo and Points for Solar Work
Toshima Ward, located in the northwestern part of central Tokyo, is an area where commercial and residential zones spread around Ikebukuro. The official page of Toshima Ward provides hazard maps for flooding and internal water (Kanda River basin, Shakujii River and Shirako River basin, Sumida River and Shinkawaguchi River basin) as well as hazard maps for landslides.
We have summarized the points to consider when installing solar panels and storage batteries in the residential environment of Toshima Ward below. (Tap to open)
View the characteristics of Toshima Ward and points for solar construction
■ Check the installation location of storage batteries and power conditioners against the hazard map assumptions
The flood and internal water hazard map of Toshima Ward assumes a total rainfall of 690mm and a maximum hourly rainfall of 153mm, indicating that the extent and degree of flooding can vary depending on the rainfall pattern, land shape, and the condition of rivers and sewers. When deciding on the installation location for storage batteries and power conditioners, it is advisable to check the flooding assumptions for your residence on the hazard map and consider the height and position of the installation for peace of mind.
■ Tokyo’s annual sunshine duration is approximately 1,927 hours
The Japan Meteorological Agency’s average value (1991–2020) indicates that Tokyo’s annual sunshine duration is about 1,927 hours.
Since power generation varies by season, it is important to conduct a year-round power generation simulation and select the capacity of the storage battery according to the times when electricity is used the most.
■ In areas where commercial and residential zones are close, check the shadows of surrounding buildings
In places where commercial facilities, buildings, and residences are closely built, the shadows cast by surrounding buildings vary for each house depending on the orientation and height of the roof or rooftop. Since solar panels generate less power when shaded, Kakeru Koumuten creates layout diagrams based on blueprints and site conditions, allowing you to confirm through power generation simulations.
■ The district’s subsidy is for “residential properties occupied by the owner.” Consent from the owner is required for rentals
The subsidy from Toshima Ward is applicable to residential properties occupied by the owner that have a registered address in the ward, and for rental properties, obtaining consent from the owner for installation is a prerequisite. In rental properties and apartment buildings, it may be necessary to confirm the installation location and ownership relations, so please consult us in advance.
■ In places with narrow front roads, plan scaffolding and equipment delivery carefully
In areas with narrow front roads or where surrounding buildings are close together, careful planning for scaffolding and equipment delivery may be necessary. Kakeru Koumuten will respond according to the site with our own scaffolding team and owned scaffolding materials.
■ Check the roof condition according to the age of the building
For buildings that have been around for many years, it is important to check the condition of the roofing materials and substrate before installing solar panels. Depending on the roof’s condition, installing them simultaneously with roof renovations can help reduce future costs for removing and reinstalling solar panels.
■ Subsidies must be applied for before construction in Tokyo and after completion in Toshima Ward
In Tokyo, prior application for installation is required for the Cool Net Tokyo subsidy. In Toshima Ward, the Eco Housing Promotion Subsidy does not require application before construction and should be applied for after the completion of the work. It is important to check the procedures and timelines for each program in advance, in conjunction with the timing of the construction.
Our company serves Kanagawa Prefecture and Tokyo, and we handle many exterior construction and solar projects in Toshima 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 Toshima Ward, Tokyo
Kakeru Koumuten Co., Ltd. accepts requests throughout Kanagawa Prefecture and all of Tokyo.
List of Areas in Toshima Ward, Tokyo
Ikebukuro, Toshima Ward / Ikebukuro Honcho, Toshima Ward / Kanamecho, Toshima Ward / Kamikebukuro, Toshima Ward / Kita-Otsuka, Toshima Ward / Komagome, Toshima Ward / Sugamo, Toshima Ward / Senkawa, Toshima Ward / Zoshigaya, Toshima Ward / Takada, Toshima Ward / Takamatsu, Toshima Ward / Chihaya, Toshima Ward / Nagasaki, Toshima Ward / Nishi-Ikebukuro, Toshima Ward / Nishi-Sugamo, Toshima Ward / Higashi-Ikebukuro, Toshima Ward / Minami-Ikebukuro, Toshima Ward / Minami-Otsuka, Toshima Ward / Minami-Nagasaki, Toshima Ward / Mejiro, Toshima Ward
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・Trust Kakeru Koumuten for exterior renovations in Toshima, Tokyo!
・Kakeru Koumuten Co., Ltd. construction achievements
・Kakeru Koumuten Co., Ltd. aftercare services
・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 tips included!
・What are the installation costs for solar power generation? Comprehensive tips to reduce costs!
・What are the best locations for installing solar power generation? Points to consider for site selection!
・Check here for 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!
