Leave Your Solar Panel Installation Work in Toshima, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and battery installation in
Toshima Ward, Tokyo,
Kakeru Koumuten is at your service!
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 Ward”
“Costs for Solar Panel and Battery Installation”
“Subsidies Available for Solar System Installation in Toshima Ward”
We will also explain the above three points!
Installing solar panels carries 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 Why Kakeru Koumuten is Chosen for Solar Panel Installation in Toshima, Tokyo
- Roof Inspection Before Installing Solar Panels
- Subsidies and Grants That May Be Applicable 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 Installer in Toshima, Tokyo
- Benefits of Introducing Solar Equipment
- Points to Note 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 Installer in Toshima, Contact Kakeru Koumuten
- Characteristics of Toshima, Tokyo and Points for Solar Installation
- Service Area in Toshima, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Toshima, Tokyo
Regarding why our company is entrusted with solar panel installation by customers in Toshima, Tokyo,
One reason is that “Kakeru Koumuten serves Kanagawa and Tokyo as its service areas.” Additionally,
“Our unique strengths in solar panel installation that cannot be imitated by other companies” have received high praise from many customers.
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 the installation of solar panels may be caused by insufficient checks on the roof and waterproofing at the installation site.
Even if you are knowledgeable about solar panels, there are cases where the roof and waterproofing at the installation site are outside your expertise, so caution is necessary.
It is reassuring to have knowledge about the roof to avoid maintenance and troubles 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 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 Ownership of Scaffolding Materials
To ensure safety during work on the roof, we own the necessary scaffolding materials for temporary scaffolding based on construction conditions, allowing us to assemble scaffolding ourselves.
By performing scaffolding work with our own scaffolding team instead of outsourcing, we can also cut costs related to scaffolding work.
We have scaffolding materials for approximately 50 single-family homes!
Even in the urban area of Toshima Ward, our scaffolding team will plan the scaffolding according to the site conditions.
Storage of materials in our large warehouse
We store roofing materials and paints, and we can also store removed solar panels.
By ordering a large quantity of materials at once, we canpurchase materials at a lower cost!
Additionally, we always have a stock of roofing materials, so we can providequick responses in emergencies!
Sorting and transportation of waste materials in-house
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 the 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 show the structure, allowing for detailed explanations!
3.All Work Performed by Our Own Team
One of Kakeru Koumuten’s major strengths is all work performed by our own team.
By maintaining a consistent system from inquiry to project completion, Kakeru Koumuten can provide high-quality roof remodeling at reduced costs.
Additionally, one representative will handle everything from the estimate to project completion.
Since the same person is responsible throughout, communication can be smooth without changes in sales or construction management representatives.
We can perform consistent in-house work from temporary scaffolding installation to exterior wall painting and roof remodeling!
4. Various Permits and Skilled Workers
We have obtained construction industry permits and permits for industrial waste collection and transportation!
We also have nationally certified sheet metal and painting technicians on staff, and we are confident in our construction techniques.
We can also handle large-scale roofing projects such as factories!
5. Warranty and Aftercare
In addition to the manufacturer’s warranty, our solar panel installation work comes with our own workmanship warranty (leakage warranty)!
(The workmanship 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 workmanship warranty is separate from the manufacturer’s product warranty, and the scope and conditions vary depending on the warranty details.)
Aftercare maintenance is available annually, and we send out notification DM every year.
If you have any questions about the warranty, please click on the image above!
6. Flexible and Prompt Response
Our company is equipped to handle various roof troubles and situations.
Even if we cannot access the roof at high altitudes, we can respond using a drone!
During leakage investigations, we can also conduct inspections using a thermal imaging camera.
If the power generation of the solar panels decreases due to dirt, we can also provide cleaning with a specialized brush.
We will respond according to the customer’s wishes.
7. Human Resource Development
To improve skills, we create various roof 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 Clear Materials and Simulations
At Kakeru Koumuten Co., Ltd., we provide not only estimates, layout diagrams, and power generation simulations, but also a solar installation guidebook and a financial simulation that takes into account loan interest rates and electricity costs.
The financial simulation can project cumulative income and expenses over 20 to 30 years.
Even customers who are not familiar with solar installations will find our materials easy to understand, including important points and potential drawbacks!
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.
It is crucial to confirm before installation whether it is safe to place them directly on the current roof, as this is the key point to prevent leaks and unnecessary expenses!
Kakeru Koumuten, specializing in roofing work, has summarized the items to check before installation.
| 1. Type of roofing material and age | The method of securing the panels varies depending on the roofing material, such as slate, tiles, metal roofs, or flat roofs (roof waterproofing). If the remaining lifespan of the roofing material is short, we may suggest a roof renovation first. |
| 2. Condition of the substrate and waterproof sheet | If the sheathing or roofing (waterproof sheet) beneath the roofing material is damaged, it can affect the fastening strength and waterproofing. We will also check for 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, can affect power generation. We will create a layout diagram from the drawings and the site, and you can confirm it with the power generation simulation. |
| 4. Shape of the roof and installable area | The number of panels (installation capacity) that can be placed depends on the shape and size of the roof. The number of panels that can be installed varies with their size, so we will compare based on the total output of the roof. |
| 5. Method of securing and waterproofing details | We will check whether the method involves drilling holes in the roofing material or securing it with brackets. The method of securing varies by technique, so please confirm the waterproofing treatment of the fastening parts at the time of the estimate. |
| 6. Weight of the roof | The roof will become heavier due to the panels. After investigating the existing roof, substrate, and load-bearing capacity, replacing with lighter roofing materials may also be an option if necessary. |
| 7. Location of equipment installation and wiring | We will confirm the installation locations for the power conditioner and storage battery, as well as the wiring route to the distribution board. The length of the wiring will also affect costs. |
Securing Methods and Checkpoints 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) | Waterproofing treatment of fixed parts, cracks or deterioration of slate, condition of the substrate. If deterioration is significant, consider roof overlay (cover method) or replacement first. |
| Tile Roof | Fixed with brackets and methods suited to 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 lighter 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 framework | Type and deterioration status of the waterproof layer, waterproofing around the framework. Consider in conjunction with the timing of waterproofing work. |
If you renovate the roof 10 to 20 years after installation, additional costs for removing and reinstalling solar panels will apply. 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 in-house, so please consult us according to the condition of your roof!
▶ Click here for roof renovations in Toshima, Tokyo
Potential Subsidies and Grants
If you are introducing solar panels or storage batteries in Toshima, Tokyo, there may be applicable systems from “the national government,” “Tokyo,” and “Toshima City.”
The following information is based on the official pages of each system 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 within Tokyo, with a system capacity of less than 50kW. Pre-application before installation is required. | Existing homes: 150,000 JPY/kW for 3.75kW or less (maximum 450,000 JPY), 120,000 JPY/kW for over 3.75kW New homes: 120,000 JPY/kW for 3.6kW or less (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 within Tokyo, which must be SII registered devices. 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 | Individuals residing in the ward with a registered address 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 devices by SII, among other requirements. No application is required before construction, and applications are made after completion. | Solar power generation: 20,000 JPY per 1kW output (maximum 80,000 JPY) Storage systems: 10,000 JPY per 1kWh storage capacity (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. The ward’s official page states that as of October 5, 2026, the planned grant amount is 52% of the budget. |
| 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 1kWh (subsidy rate within 30% and maximum 600,000 JPY per application). | As of May 29, 2026, the budget has been reached, and the public recruitment has ended (applications are currently not accepted). |
| National “Mirai Eco Housing 2026 Project” (Renovation) | The storage battery is one of the eligible facilities, but it must be combined with essential 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 subsidies, 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 you will receive the subsidy. The Toshima Ward subsidy is on a first-come, first-served basis, and applications will close once the budget is reached. You can combine subsidies as long as the national and Tokyo government do not prohibit it. Procedures differ by program, so please confirm before contracting and starting work.
At Kakeru Koumuten Co., Ltd., we will guide you on eligibility after confirming the conditions for each program.
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 eligible systems are those using certified solar modules installed newly in residential homes or on their premises, with a capacity of less than 50 kW. A pre-application before installation is required.
The subsidy amount for existing homes is 150,000 JPY/kW for up to 3.75 kW (maximum 450,000 JPY), and 120,000 JPY/kW for exceeding 3.75 kW. 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 subsidy and performance report is from June 30, 2026, to March 30, 2029. For details on eligible equipment and conditions, as well as budget status, please check the official page.
👉 Cool Net Tokyo | Official page for solar power generation is here
Tokyo “Reiwa 8 Year Household Storage Battery Promotion Project”
Tokyo is also providing subsidies for storage batteries installed newly in residential homes. The subsidy amount is 100,000 JPY per kWh for storage battery packages (maximum 1,200,000 JPY/unit), and for additional storage battery units, it is 60,000 JPY per kWh (maximum 720,000 JPY/unit), with additional amounts for participation in DR demonstrations.
The eligible equipment must be 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 also be made for storage batteries alone. The application for subsidy and performance report has been open since June 30, 2026.
👉 Cool Net Tokyo | Official page for storage batteries is here
Toshima Ward “Eco Housing Promotion Subsidy”
In Toshima Ward, a “Eco Housing Promotion Subsidy” is being implemented for those who install environmentally friendly equipment in residential properties 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 in the ward and use the equipment in a residential property they occupy; 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 Co-Creation Initiative). No application is required before construction; applications are made after completion (applications will be accepted from May 25, 2026, to March 1, 2027, and must be completed by January 31, 2027, for equipment installed 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 planned grant amount ratio against the budget is reported to be 52% on the ward’s official page. If there is no prohibition on combined use from the national or Tokyo Metropolitan Government, it can be combined with other subsidies.
👉 Here is the official page of Toshima Ward (Eco Housing Promotion 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 those who are newly introducing registered storage systems that can be utilized for demand response (DR), with the fiscal year Reiwa 7 supplementary project setting a standard amount 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 also conditions such as items contracted or ordered before the grant decision are not eligible.
However, the fiscal year Reiwa 7 supplementary application amount reached the budget on May 29, 2026, and the public offering has ended (the previous year’s Reiwa 6 supplementary also ended on July 2, 2025). Applications are currently not being accepted, so please check the official site for future public offerings.
Currently, there are no subsidies confirmed for the installation of solar panels on existing homes from the national government.
👉 Here is the official site for the DR Home Storage Battery Project
Solar Panel Installation & Storage Battery Installation Price List
⇧Service Menu | Click here for costs related to Solar Panel Installation and Battery Installation
⇧Service Menu | Click here for costs related to Solar Panel Removal and Water Heater Removal
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.
Considerations for 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). Batteries are compared based on the amount of electricity they can store, expressed in kWh (kilowatt-hours).
The amount of kW that can be placed on the roof varies for each house depending 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 panels 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 area, existing roofing materials, and panel layout.)
▶ Installation Menu | Costs for Solar Panel Installation and Battery Installation
Items to Check in the Estimate (Cost Confirmation)
When comparing estimates, it is 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) should be listed. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, installation location (indoor/outdoor). Also check if it is a type that controls the battery together. |
| 3. Battery | Manufacturer, model number, capacity (kWh), range usable during power outages (entire house or specific circuits), installation location. |
| 4. Mounting Frame and Hardware | Name of the hardware suitable for the roofing material and the method of securing it (whether it is a method that drills holes or a method that clamps and secures). |
| 5. Wiring and Electrical Work | Wiring route and length, work around the distribution board, and whether there is a monitor to check power generation. |
| 6. Roof Reinforcement and Waterproofing | Details of waterproofing treatment at the fixed parts, and whether necessary roof repairs and substrate reinforcements are included. |
| 7. Applications | How much support is included for applications to the power company, certification applications for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Scope and quantity of scaffolding. If it is simultaneous with roof work or exterior painting, 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 it is tax-inclusive or tax-exclusive, conditions under which additional costs may arise, and details and duration of manufacturer and workmanship warranties. |
If the capacities differ, both the amount and power generation will change. Kakeru Koumuten Co., Ltd. welcome comparisons, so if you bring estimates from other companies, we will explain the differences for each item!
Self-Estimate and Profit Simulation for Solar Power Generation
With the simulator above,
you can get an estimated quote and income 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 obtain an estimated quote and income simulation!
*The simulation results are estimates. Actual income 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
| Work Details |
| Solar Panel Installation Battery Installation |
| Existing Roofing Material |
| Horizontal Metal Roof (Super Galtect) |
| Installation Capacity |
| Solar Panel: 4.3kW Battery: 5kWh range |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Arrangement |
| Fixed by catching the horizontal metal roof with catch type hardware (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 Estimated 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 will be granted. |
Our Proposal
We visited to provide an estimate and created a layout diagram for the solar panels from 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 subsidy to 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 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 power but also about roofs
● Confirm the existence of warranties and aftercare maintenance
● Obtain estimates from multiple contractors (three companies are 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.
Have knowledge not only about solar panels but also about roofs
Defective 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 installed on a severely deteriorated roof causing leaks
・Solar panels installed on a roof with a short lifespan, requiring renovations for removal and reinstallation within a few years
・Misjudgment of the type of waterproofing leading 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 maintenance
When choosing a solar installation contractor, confirm the existence of warranties. It is important to check not only the duration of the warranty but also the scope, disclaimers, and cost conditions.
While the solar panels and battery storage units come with manufacturer warranties, also check for the existence of installation warranties in case leaks occur after installation!
For contractors that offer installation warranties, if leaks occur after installation within the warranty period and conditions, they may be able to address the issue under warranty.
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 may occur in areas that are not visible, so you may not notice them yourself.
By conducting inspections in after-sales maintenance, you can easily prevent major repairs or breakdowns by discovering abnormalities early!
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, a roof renovation may be required to provide the warranty.)
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 solar panel installation, be sure to obtain estimates from multiple contractors.
Even with 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 cost, we recommend obtaining estimates from multiple contractors.
When comparing estimates, please check carefully for:
“Verification of estimate items”
“Types of solar panels”
“Warranties and after-sales services”
Make sure to compare these details closely! If the quality of auxiliary materials is low or if steps are skipped, costs can be reduced, so avoid making decisions 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 and storage 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 processed 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.
Be sure to complete the procedures specified for each system (for Tokyo’s subsidies, a pre-application is required before installation) before proceeding with the construction! In Toshima Ward, pre-application for subsidies is not necessary, and applications are made after the completion of construction!
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 reviewed before the grant is awarded! For the subsidy in Toshima Ward, the application is made after the completion of the work, and it will also go through a review process before the grant is awarded! (The procedure varies 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 installing solar panels are summarized in the following five points!
Benefit 1: Economic Advantage
The biggest advantage of installing 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 amount of electricity purchased from the utility company by consuming the electricity generated!
As electricity prices rise, the ability to cover your consumption with solar power becomes increasingly 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 in 2026. After the fifth year, it is generally more advantageous to use the electricity at home (self-consumption), making the combination with a storage battery a viable option.
👉 For details on purchase prices and periods, visit the Agency for Natural Resources and Energy
Benefit 2: You Can Utilize Subsidies!
The conditions and amounts of subsidies vary by prefecture and municipality, but if you meet the requirements, you may be able to utilize subsidies!
Reducing the actual burden through subsidies is a significant advantage!
In the case of Toshima Ward, in addition to national and Tokyo metropolitan systems, there may be eligibility for the Toshima Ward Eco-Housing Promotion Subsidy (for solar power systems and storage systems) (the ward’s subsidy requires application 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 mitigation of global warming by reducing carbon dioxide emissions and dependence on fossil fuels.
Since solar panels do not produce noise or exhaust gases during the power generation process, they are considered an environmentally friendly method of generating electricity. (Devices such as power conditioners may produce operational noise.)
Benefit 4 Expect heat insulation effects!!
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 expected heat insulation effects!
(Note that this does not improve the insulation performance of the building itself.)
Benefit 5 Electricity can be used even during power outages!!
If a storage battery is installed, it becomes 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 are incurred
One maintenance cost that is often overlooked is the roof where the 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 the 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 increases depending on the roofing material
The methods for securing slate roofs and tile roofs vary depending on the construction method, but when securing materials and substrates with screws or similar fasteners, waterproofing at the fastening points becomes crucial.
In methods that involve making holes in the roof, the risk of leaks inevitably arises.
Of course, we will ensure thorough waterproofing, 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
With the addition of 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 outputs 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 by Total Output of the Roof
When installing solar panels on the roof, it is important to consider how much electricity can be generated in the limited area, and the more electricity 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 at first glance that the higher output panel is better.
However, if the size of the panels does not fit well with the roof, “20 panels of 350W can be installed, while only 15 panels of 400W can be installed,” which can lead to different installation capacities on the same roof due to the size differences.
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 represent total output (kW). The actual electricity generation (kWh) will vary based on conditions such as roof orientation, slope, and shading.
Choosing Method 2: Compare by 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 warranty values are benchmark figures for guarantees and do not indicate actual degradation rates or power generation amounts.
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 vary by manufacturer.
Some manufacturers offer a 30-year warranty for output, while others provide a 10-year warranty, so it varies widely!
The longer the warranty, the better, so be sure to check the warranty periods and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar Power and Storage Battery Installation in Toshima Ward
We have compiled frequently asked questions from customers considering the installation of solar panels and storage batteries in Toshima Ward. (Tap to open the answers)
How much does it cost to install solar panels and storage 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 + storage battery, completed in April 2025), it was 2.2 million yen to 2.3 million yen.
Guidelines by capacity are published on the solar panel installation and storage battery installation pricing page. We will create a layout diagram from the drawings and on-site survey and provide a free estimate!
Are there any subsidies available for solar power and storage battery installation in Toshima Ward?
As of October 7, 2026, Tokyo’s subsidies for solar power generation and storage batteries (Cool Net Tokyo) are accepting pre-applications. For storage batteries, only SII registered devices (registered products for Reiwa 8) are eligible from pre-applications made after October 1, 2026. 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 storage 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 planned grant amount ratio against the budget is 52% (first-come, first-served, ending once the budget is reached). The national DR household storage battery project has ended its public recruitment.
The application status may change, so 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 construction is completed. Procedures differ by program.
The order of procedures varies by program, so 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 method of securing varies depending on the construction method, and when securing brackets to the roofing material or substrate, waterproofing treatment of the fixed parts is essential.
Kakeru Koumuten Co., Ltd. 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 (cover method) or replacement 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 advantageous 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 applications can also be made for storage batteries alone. You can compare “solar panels only” and “solar panels + storage batteries” through a financial simulation.
How many kW can be installed on my roof? Is it okay for a north-facing roof or one 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 from 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 shading caused 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 panels 4.3 kW + storage battery), it took about 3 days. The duration may vary depending on whether roofing work is done simultaneously or the shape and installation capacity of the roof.
Also, please note that there will be an additional period for applications 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 (less than 10 kW), the selling price from 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 fiscal year 2026.
The idea is to recover 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 guidance DM and visits customers who wish for inspections. We can also clean solar panels with a special brush if the power generation decreases due to dirt.
The roof is a place that is difficult to check by yourself, so 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 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 company in Toshima Ward, please consult Kakeru Koumuten
Our company handles many exterior renovations, including solar panel installations, roof work, and exterior wall work in Toshima Ward, Tokyo.
We receive requests from many customers, including renovation companies and real estate agencies, who have contacted us!
Kakeru Koumuten Co., Ltd. promises “high-quality renovations at low costs”, and we have received positive feedback from numerous 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 all exterior renovations, not only roof overlay work and re-roofing but also partial roof repairs, exterior painting, and exterior wall cover methods.
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 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 specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s position and propose the best construction plan!
We are confident that we will not be outdone in terms of cost, quality, and organization compared to other companies in exterior work!
We are confident, so we welcome competitive quotes!
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 of 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 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 installation
■ Check the installation location of storage batteries and power conditioners against the hazard map
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 rainfall patterns, land shape, and the condition of rivers and sewage systems. 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 hours are approximately 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), Tokyo has about 1,927 hours of sunshine annually.
Since power generation varies by season, it is important to conduct annual power generation simulations and select the capacity of storage batteries to match the times when electricity is used most.
■ In areas where commercial and residential zones are close, check for shadows from surrounding buildings
In locations where commercial facilities, buildings, and residences are in close proximity, the shadows cast by surrounding buildings can 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, and confirms this through power generation simulations.
■ The district’s subsidy targets “residences occupied by the owner.” Consent from the owner is required for rentals
The subsidy from Toshima Ward is applicable to installations in residences occupied by the owner that have a registered address in the ward, and for rental properties, consent from the owner for installation is required. In rental properties or apartment buildings, it may be necessary to confirm the installation location and ownership relations, so please consult us in advance.
■ In areas with narrow front roads, plan scaffolding and equipment delivery carefully
In locations 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 to site conditions with our own scaffolding team and scaffolding materials.
■ Check the roof condition according to the age of the building
For buildings that have been constructed for many years, it is important to check the condition of the roofing materials and substrate before installing solar panels. Depending on the condition of the roof, installing them simultaneously with roof renovations can help reduce future costs for removing and re-installing solar panels.
■ Subsidy applications: Tokyo before construction, Toshima Ward after completion
In Tokyo, prior application for installation to Cool Net Tokyo is required for subsidies. In Toshima Ward, the Eco Housing Promotion Subsidy does not require application before construction and can be applied for after the work is completed. It is important to check the procedures and timelines for each system in advance, in conjunction with the timing of the construction.
Our company serves Kanagawa Prefecture and Tokyo, and we handle many exterior and solar construction 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
・Exterior wall painting in Toshima, Tokyo, is entrusted to Kakeru Koumuten!
・Roof renovations in Toshima, Tokyo, are entrusted to Kakeru Koumuten!
・Exterior renovations in Toshima, Tokyo, are entrusted to Kakeru Koumuten!
・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 key points!
・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 solar power installation? Key points for site selection included!
・Find out more about solar power generation estimates here!
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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!
