Leave Your Solar Panel Installation Work in Koto City, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and battery installation in
Koto City, 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 installation and battery installation considering roofs and waterproofing!
“How to choose a solar panel contractor in Koto City”
“About the costs of solar panel and battery installation”
“About subsidies applicable for solar system installation in Koto City”
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 obtainingthree or so estimates!
Table of contents for this article (tap to open/close)
- Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Koto City, Tokyo
- Roof Inspection Before Installing Solar Panels
- Possible Subsidies and Grants Available in Koto City
- Price List for Solar Panel and 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 Koto City, 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 Battery Installation in Koto City
- If You Are Looking for a Solar Panel Installer in Koto City, Contact Kakeru Koumuten
- Characteristics of Koto City, Tokyo and Key Points for Solar Installation
- Service Area in Koto City, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Koto City, Tokyo
Regarding why we are entrusted with solar panel installation by customers in Koto City, Tokyo,
One reason is that “Kakeru Koumuten serves Kanagawa and Tokyo as its service areas.” However,
“We have unique strengths in solar panel installation that cannot be imitated by other companies,” which has 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 estimates from any number of companies!
1. We Can Also Handle Exterior Renovations Aside from 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 is reassuring to have someone knowledgeable about the roof to avoid maintenance and troubles after construction!
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 troubles 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 based on construction conditions and can assemble scaffolding in-house.
By not outsourcing scaffolding work and using our own scaffolding team, we can also cut costs for scaffolding construction.
We own scaffolding materials for approximately 50 single-family homes!
Even in Koto Ward, where low-lying areas near water spread out, our in-house scaffolding team will plan scaffolding according to the local 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, 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 you have 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 show 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 having Kakeru Koumuten handle everything from inquiries to project completion in a consistent manner, we can keep costs down while providing high-quality roof renovations.
Additionally, one representative will assist you from the estimate to the completion of the work.
Since the same person will handle everything, including sales and construction management, smooth communication is possible.
We can provide consistent in-house construction from temporary scaffolding installation to exterior wall painting and roof renovations!
4. Various Permits and Skilled Workers
We have obtained permits for construction work and 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 roof work for factories and other facilities!
5. Warranty and Aftercare
In addition to the manufacturer’s warranty for solar panel installation work, we also provide our own construction warranty (leakage warranty)!
(The construction warranty for solar panel installation is 10 years. Depending on the condition of the roof before installation, we may not be able to provide a warranty unless a roof renovation is performed. The construction warranty is separate from the manufacturer’s product warranty, and the scope and conditions vary depending on the warranty details.)
Aftercare is available every year, and we send out annual reminder DM notifications.
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 roofing troubles and situations.
If you are unable to 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 solar panels decreases due to dirt or other factors, we can provide cleaning with specialized brushes.
We will respond according to the customer’s wishes.
7. Human Resource Development
To enhance skills, we create various roofing models and conduct practical training.
Since the construction methods vary depending on the shape and slope of the roof, we regularly provide technical training so that each staff member can handle various cases.
8. Creation of Easy-to-Understand Materials and Simulations
Kakeru Koumuten provides not only “estimates,” “layout diagrams,” and “power generation simulations” but also a “solar construction guidebook” and “profit and loss simulations” that take into account loan interest rates and electricity costs.
Profit and loss simulations can be created for projected cumulative profits and losses over 20 to 30 years.
Even customers who are not familiar with solar construction will receive materials that clearly summarize important points and disadvantages!
We encourage you to obtain comparative estimates and 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 or 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 summarized the items to check before installation.
| 1. Types of Roofing Materials and Age | The fixing method varies depending on the roofing materials such as slate, tiles, metal roofs, and flat roofs (roof waterproofing). If the remaining lifespan of the roofing material is short, we may suggest a roof renovation first. |
| 2. Condition of Substrate and Waterproof Sheet | If the sheathing boards or roofing (waterproof sheet) under the roofing material are damaged, it will affect the fixing strength of the fittings 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, can affect the amount of electricity generated. We will create a layout diagram from the drawings and the site, and you can confirm it with a power generation simulation. |
| 4. Shape of the Roof and Usable Area | The number of panels (installation capacity) that can be placed depends on the shape and size of the roof. Since the number of panels that can be installed varies depending on the panel size, we will compare based on the total output of the roof. |
| 5. Fixing Method and Waterproofing Details | We will check whether the method involves drilling holes in the roofing material for fixing or using fittings to secure the roofing material. The fixing method varies depending on the technique, so please confirm the waterproofing treatment method for the fixing 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 check the installation location of the power conditioner and storage battery, as well as the wiring route to the distribution board. The length of the wiring will also affect the cost. |
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 to the roof material and substrate with screws) | Waterproof treatment of fixing parts, cracks or deterioration of slate, condition of substrate. If deterioration is advanced, consider roof overlay (cover method) or replacement first. |
| Tile Roof | Fixed with brackets and methods suitable for the type of tile (even methods that do not drill holes in the tiles will fix to the substrate) | Type and condition of tiles, substrate, load-bearing capacity. Depending on the investigation results, there may be methods to replace with lightweight roofing materials before installation. |
| Metal Roof (Horizontal and Vertical) | Fixed with catch-type brackets that grip the roof material (depends on the combination of roof material and brackets) | Whether the roof material and brackets are compatible, installation conditions from the roof material manufacturer. If compatible, methods that do not drill holes may be available. |
| Flat Roof / Rooftop | Fixed by installing a frame | Type and deterioration status of the waterproof layer, waterproofing around the frame. Consider in conjunction with the timing of waterproofing work. |
If you perform roof renovations 10 to 20 years after installation, there will be additional costs for 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 in-house, so please consult us according to the condition of your roof!
▶ Click here for roof renovations in Koto City, Tokyo
Potential Subsidies and Grants in Koto City, Tokyo
If you are introducing solar panels or storage batteries in Koto City, Tokyo, there is a possibility that the systems of “the national government,” “Tokyo,” and “Koto City” may apply.
The following information is based on the official pages of each system as of October 7, 2026. The application status may change due to budget and application periods, 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 Introduction Promotion Project” (Cool Net Tokyo) | New installation of certified solar modules in residential properties or their premises within the Tokyo area, 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 structures, 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 Introduction Promotion Project” (Cool Net Tokyo) | New installation of storage batteries in residential properties within the Tokyo area, with SII registered equipment. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries only. 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 participating in DR demonstrations, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 |
| Koto City “Reiwa 8 Year Global Warming Prevention Equipment Introduction Subsidy (for Individual Homes)” | Owners or prospective owners of residential properties within the district, residents of rental properties (with owner consent), etc. Solar power requires a power purchase agreement with the utility company, and storage batteries must be SII registered equipment. Application must be made before construction starts. | Solar power generation: 50,000 JPY per kW (maximum 200,000 JPY) Storage battery: 10,000 JPY per kWh (maximum 100,000 JPY) If applying for both solar power and storage battery simultaneously: Solar power is 60,000 JPY per kW (maximum 240,000 JPY), storage battery is 25,000 JPY per kWh (maximum 200,000 JPY) |
From April 1, 2026 to March 15, 2027 (must arrive by this date) There is no mention of budget or first-come-first-served in the district’s materials, so please check with the district office. |
| National Government “DR Household Storage Battery Project” (Reiwa 7 Year Supplement) | New introduction 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. (Currently, applications cannot be made.) |
| National Government “Mirai Eco Housing 2026 Project” (Renovation) | Storage batteries are one of the eligible facilities, but they must be combined with essential renovations such as insulation improvements for windows (openings) and the structure; applications cannot be made for the installation of storage batteries alone. Solar panels are not included as eligible facilities. | Battery Storage: 96,000 JPY/unit | Ends as soon as the budget limit is reached. Please check the official website for the application status. |
In Tokyo, a pre-application before installation is required for subsidies, and for Koto Ward, application before construction starts is mandatory (applications after construction has started will not be accepted). If you begin construction first, you will be excluded from eligibility, and applying does not guarantee that you will receive the subsidy. Procedures and eligibility for combining different systems vary, so please confirm before signing a contract or starting construction.
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”
In Tokyo, through Cool Net Tokyo, subsidies are provided for those installing solar power generation systems in residential homes within the city. 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.
For existing homes, the subsidy amount is 150,000 JPY/kW for up to 3.75kW (maximum 450,000 JPY), and 120,000 JPY/kW for over 3.75kW. Additionally, there are extra items for mounting structures, 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 the budget status, please check the official page.
👉 Cool Net Tokyo | Official page for solar power generation is here
Tokyo “Reiwa 8 Year Household Battery Storage Promotion Project”
Tokyo is also providing subsidies for newly installed battery storage in residential homes. The subsidy amount is 100,000 JPY per kWh for battery storage packages (maximum 1,200,000 JPY/unit), and 60,000 JPY per kWh for additional 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 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 battery storage only. The application for subsidy and performance report has been accepted since June 30, 2026.
👉 Cool Net Tokyo | Official page for battery storage is here
Koto Ward “Reiwa 8 Year Global Warming Prevention Equipment Installation Subsidy (for Individual Homes)”
Koto Ward is implementing the “Global Warming Prevention Equipment Installation Subsidy” to subsidize part of the costs for those installing solar power generation systems or battery storage in homes within the ward. Application must be made before construction starts, and applications after construction has started will not be accepted.
The subsidy amount for individual residences is 50,000 yen per kW for solar power (up to 200,000 yen), and 10,000 yen per kWh for storage batteries (up to 100,000 yen). If applying for both solar power and storage batteries simultaneously, the subsidy for solar power is 60,000 yen per kW (up to 240,000 yen), and for storage batteries, it is 25,000 yen per kWh (up to 200,000 yen). A power purchase agreement with the electric company is required for solar power, and only SII registered devices are eligible for storage batteries. The application acceptance period is from April 1, 2026, to March 15, 2027 (must arrive by this date). The ward advises applying by the end of February whenever possible. Please check with the ward office regarding the budget status and the possibility of combining with other subsidies.
👉 Here is the official page of Koto Ward (for individual residences and collective housing)
National Subsidy “DR Household Storage Battery Project (Support Project for Introducing Household Storage Systems for DR Resources)”
The government has been implementing the “DR Household Storage Battery Project” to support the installation of household storage batteries.
This program targets those who are newly introducing registered storage systems that can be utilized for demand response (DR), and for the fiscal year 2025 supplementary budget, the subsidy amount is determined based on a standard amount of 34,500 yen per kWh of 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 supplementary budget for fiscal year 2025 reached the budget limit for grant applications on May 29, 2026, and the public recruitment has ended (the previous fiscal year’s supplementary budget also ended public recruitment on July 2, 2025). Applications are currently not being accepted, so please check the official site for future public recruitment.
Additionally, there are currently no subsidies confirmed for the installation of solar panels on existing homes.
👉 Here is the official site for the DR Household Storage Battery Project
Solar Panel Installation & Storage Battery Installation Price List
⇧Service Menu | Click here for costs related to Solar Panel Removal and Water Heater Dismantling
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and storage 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.
Considerations for Installation Capacity (kW) and Storage 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). Storage batteries are compared in terms of the amount of electricity they can store, represented in kWh (kilowatt-hours).
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 panels 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 rough estimates and can vary based on wiring length, scaffolding range, existing roofing materials, panel layout, etc.)
▶ Service Menu | Click here for costs related to Solar Panel Installation and Storage Battery Installation
Items to Check in the Estimate (Cost Verification)
When comparing estimates, it is common to compare different capacities and equipment by only looking at the amounts. 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 check if it is a type that controls in conjunction with a storage battery. |
| 3. Storage Battery | Manufacturer, model number, capacity (kWh), range of use during power outages (entire house or specific circuits), installation location. |
| 4. Mounting Frame and Hardware | Name of hardware suitable for roofing materials and method of securing (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, presence of a monitor to check power generation. |
| 6. Roof Reinforcement and Waterproofing | Details of waterproofing treatment at fixed points, whether necessary roof repairs and substrate reinforcements are included. |
| 7. Application | How much support is included for applications to the power company, certification application for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Scope and quantity of scaffolding. If roof work and exterior painting are done simultaneously, check that the same scope and quantity are not double counted. |
| 9. Removal and Disposal | Whether the removal of existing solar thermal water heaters or old panels and disposal costs for waste materials are included. |
| 10. Tax Classification and Warranty | Whether prices are tax-inclusive or tax-exclusive, conditions under which additional costs may arise, and details and duration of manufacturer and workmanship warranties. |
If the capacity differs, both the price and power generation will change. Kakeru Koumuten Co., Ltd. welcome price 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 obtain an approximate estimate and a profit simulation 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 approximate estimate and profit simulation!
*The simulation results are approximate. Actual profits may vary based on assumptions such as electricity rates, self-consumption ratios, selling prices, and costs for equipment inspection or replacement.
Customer Voices
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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 range |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Details |
| Fixed using catch type hardware gripping the horizontal metal roof (Catch Method) |
| Price Range |
| 2,200,000 JPY～2,300,000 JPY ※Due to the grant being provided, the actual burden amount is approximately 1,000,000 JPY Expected recovery period for construction costs: about 8 to 9 years (self-consumption) ※The grant amount and recovery estimate are based on the system and calculations at the time of construction, and may differ under the current system. |
| Construction Period |
| About 3 days |
| Completion Month |
| April 2025 |
| Inquiry Details |
| I am considering the installation of solar panels and storage batteries. I heard that grants are available, and I would like to know how much will be provided. |
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 the grant, so we explained it to the customer along with the estimate!
How to Choose a Solar Panel Installation Contractor in Koto City, Tokyo
There are many solar panel installation contractors available in Koto City, 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 presence 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
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 were installed on a severely deteriorated roof, leading to leaks
・Solar panels were installed on a roof with a short lifespan, necessitating a renovation for removal and reinstallation within a few years
・Misjudgment of the type of waterproofing led to incorrect processing 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 unforeseen troubles.
▶ Go to “Roof Verification Before Installing Solar Panels” within this article
Confirm the presence of warranties and aftercare maintenance
When selecting a solar installation contractor, make sure to check for warranties. It is important to verify not only the duration of the warranty but also the scope of coverage, exclusions, and cost conditions.
While the solar panels and battery storage units come with manufacturer warranties, also confirm whether there is a workmanship warranty in case leaks occur after installation!
For contractors that offer workmanship warranties, if leaks occur after installation, they may be able to address the issue under the warranty, provided it falls within the warranty period and conditions.
Additionally, some contractors offer after-service separate from the warranty, so be sure to check if the contractor you are considering has after-service.
Changes or damage on the roof may occur in areas that are not visible, so there is a possibility that customers may not notice them.
By conducting inspections during after-maintenance, we can easily detect abnormalities early, preventing major repairs or failures!
Kakeru Koumuten Co., Ltd. provides a rain 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 unless roof renovations are performed.)
We also conduct after-maintenance and send out DM every year!
Please check the DM, and if you wish, we will visit you for after-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 for the same manufacturer and the same construction content, costs may vary, and warranties and after-services may differ.
Additionally, obtaining multiple estimates makes it easier to negotiate prices.
To request from your desired contractor at a lower price, we recommend obtaining estimates from multiple contractors.
When comparing estimates,
“Check the items in the estimate”
“Type of solar panel”
“Warranties and after-services”
and make a careful comparison to make your decision! If the rank 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 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.
There are systems that require personal applications and cannot be handled by the contractor, as well as systems that require prior application before installation, so it is reassuring to have a contractor who can support the preparation of necessary documents and the flow of procedures.
Complete the procedures specified for each system (for Tokyo’s subsidy, prior application before installation; for Koto Ward’s grant, application before construction starts) before proceeding with the 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 granted after a review! (The procedure may vary depending on the system)
▶ Go to “Subsidies and Grants that May Be Applicable in Koto 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!
While 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 ability to cover your consumption with solar power becomes increasingly attractive!
If you plan to use the generated electricity at night, the installation of a storage battery is essential!
Furthermore, the selling price (FIT) for residential use (under 10kW) will be set at “24 yen/kWh for the first four years, and 8.3 yen/kWh from the fifth to the tenth year” for certifications after October 2025, and the same price will apply for the 2026 fiscal year. After the fifth year, it is generally more advantageous to use it in your home (self-consumption) rather than selling it, making the combination with storage batteries a viable option.
👉 Ministry of Economy, Trade and Industry | For purchase prices, periods, etc., click here
Benefit 2: You Can Utilize Subsidies!
The conditions and amounts of subsidies vary by prefecture and municipality, but if you meet the criteria, you may be able to utilize subsidies!
Reducing the actual burden amount through subsidies is a significant advantage!
In Koto Ward, in addition to national and Tokyo Metropolitan systems, there is a possibility of being eligible for Koto Ward’s global warming prevention equipment installation subsidy (the ward’s subsidy requires an application before the start of construction).
Benefit 3: Environmentally Friendly!
Solar power generation leads to a reduction in carbon dioxide emissions and decreases dependence on fossil fuels, contributing to the mitigation of global warming.
Solar panels themselves do not produce noise or exhaust gases during the generation process, making them an environmentally friendly method of power generation. (However, devices such as power conditioners do have operational noise.)
Advantage 4 Expect heat insulation effects!!
By installing the panels on the roof or rooftop, they block direct sunlight from hitting the roof.
Especially in summer, it can help suppress the rise in roof temperature, so heat insulation effects can be expected!
(Note that this does not improve the insulation performance of the building 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 such as power outages!
Even without a storage battery, if you have a power conditioner with autonomous operation functionality, you may be able to use electricity from a dedicated outlet during daytime generation.
(Note that 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
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 reattaching the solar panels.
If the existing roof is deteriorating, 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 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 using screws or other fasteners to secure the roofing material and substrate, waterproofing treatment at the fixed points becomes crucial.
In methods that involve making holes in the roof, the risk of leaks inevitably arises.
Of course, we will ensure proper 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
Since solar panels will be placed on the roof, it 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 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!
The sizes of solar panels vary by manufacturer, and their outputs differ as well.
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,” meaning that the number of panels that can be installed on the same roof can differ due to the size of the panels.
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 electricity generation (kWh) will vary depending on conditions such as the roof’s 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 value is a benchmark for guarantees and does not indicate the actual degradation rate or power generation amount.
Choosing solar panels while considering the degradation rate, not just the initial output, 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.
Regarding output warranties, some manufacturers offer a 30-year warranty, while others provide a 10-year warranty, making it quite varied!
Longer warranties are generally 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 Koto Ward
We have compiled frequently asked questions from customers considering the installation of solar panels and storage batteries in Koto Ward. (Tap to open the answers)
How much does it cost to install solar panels and storage batteries in Koto 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 for different capacities 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 and storage battery installation in Koto 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 (products registered in Reiwa 8) are eligible from pre-applications made after October 1, 2026. The application period for Koto Ward’s global warming prevention equipment introduction subsidy is until March 15, 2027 (must arrive by this date), and applications must be made before the start of construction. The national DR household storage battery project has ended its public recruitment.
Since the acceptance 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 must be completed before construction. Tokyo’s subsidies require pre-application before installation, and Koto Ward’s grants require application before the start of construction; if you install first, you will be ineligible. Procedures differ by program.
Since the order of procedures varies by program, please confirm before signing a contract and starting construction.
Can solar panels be installed on slate roofs? I’m worried about leaks.
It is possible to install on slate roofs, 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 hardware 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 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 within 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 during the on-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 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 installable capacity 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 on-site survey, and provide you with the installation capacity and generation simulation.
In Koto Ward, the appearance of the city varies from the waterfront area to residential areas, and the shadows cast by neighboring houses and surrounding buildings differ from one house to another. You can check the expected generation amount through the 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 if roofing work is done simultaneously or depending on the shape of the roof and installation capacity.
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 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 for 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 DM notices and visits customers who wish to have inspections. We can also clean solar panels with a special brush if the generation amount decreases 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 the 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 Koto City, please consult Kakeru Koumuten Co., Ltd.
Our company handles a wide range of exterior renovations, including roof work and exterior wall work, in Koto City, Tokyo, including solar panel installations.
We have received 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 achievements every year and 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 about 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 construction!
We are confident, so we welcome competitive quotes!
Estimates are completely free, and if you find our company inferior to others, you are free to decline!
Characteristics of Koto City, Tokyo and Points for Solar Work
Koto Ward, Tokyo, is located at the southeastern tip of Tokyo, bordered by the Sumida River to the west, the Arakawa River to the east, and facing Tokyo Bay to the south. The official page of Koto Ward states that the area is 42.99 km2 and includes many towns such as Aomi, Ariake, Toyosu, Kameido, and Fukagawa.
We have summarized the points to consider when installing solar panels and storage batteries in Koto Ward’s residential environment below. (Tap to open)
View the characteristics of Koto Ward, Tokyo, and points for solar installation
■ In areas with low-lying waterfronts, check the installation locations for storage batteries and power conditioners against flood risk
Koto Ward is surrounded by the Sumida River, Arakawa River, and Tokyo Bay, with many rivers and canals within the ward. When deciding on the installation locations for storage batteries and power conditioners, it is reassuring to check the flood risk for your residence on a hazard map and consider the height and position of the installation.
■ Consider salt wind in areas close to Tokyo Bay, rivers, and canals
In areas near Tokyo Bay, rivers, and canals, you may be affected by winds containing salt. It is important to check the condition of the metal parts of panels, frames, and outdoor equipment during inspections after installation.
■ Tokyo’s annual sunshine duration is about 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), Tokyo’s annual sunshine duration is about 1,927 hours.
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 the most.
■ In areas with different urban landscapes from the bay area to Fukagawa and Joto, check for shadows from neighboring houses
Koto Ward features diverse urban landscapes, from high-rise residential buildings in the bay area to residential areas in Fukagawa, Kameido, and Oshima. The way shadows are cast by neighboring houses and surrounding buildings varies from one house to another. Kakeru Koumuten creates layout diagrams based on blueprints and the actual site conditions, allowing for verification through power generation simulations.
■ In residential areas with narrow roads, plan scaffolding and equipment delivery carefully
In densely built residential areas, the front roads may be narrow, requiring careful planning for scaffolding and equipment delivery. 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 houses that have been built for several 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 require separate prior procedures from Tokyo and Koto Ward
Tokyo’s subsidies require pre-application to Cool Net Tokyo, and Koto Ward’s subsidy for introducing equipment to prevent global warming requires application before construction begins. It is essential to check the procedures and conditions for each system in advance, in line with the timing of the construction.
Our company serves Kanagawa Prefecture and Tokyo, and we handle many exterior and solar construction projects in Koto 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 for any urgent issues!
Service Area in Koto Ward, Tokyo
Kakeru Koumuten accepts requests throughout Kanagawa Prefecture and all of Tokyo.
List of Areas in Koto City, Tokyo
Aomi, Koto City / Ariake, Koto City / Ishijima, Koto City / Uminomori, Koto City / Umibe, Koto City / Eitai, Koto City / Edagawa, Koto City / Echujima, Koto City / Oogibashi, Koto City / Oshima, Koto City / Kameido, Koto City / Kitasuna, Koto City / Kiba, Koto City / Kiyosumi, Koto City / Saga, Koto City / Sarue, Koto City / Shiohama, Koto City / Shiohama, Koto City / Shinonome, Koto City / Shirakawa, Koto City / Shindaibashi, Koto City / Shin-Kiba, Koto City / Shinsuna, Koto City / Sumiyoshi, Koto City / Sengoku, Koto City / Chida, Koto City / Takahashi, Koto City / Tatsumi, Koto City / Chuo Bōhatee, Koto City / Toyo, Koto City / Tokiwa, Koto City / Tominaka, Koto City / Toyosu, Koto City / Higashisuna, Koto City / Hiranomachi, Koto City / Fukagawa, Koto City / Fukuzumi, Koto City / Fuyuki, Koto City / Koishiba, Koto City / Botan, Koto City / Minamisuna, Koto City / Miyoshi, Koto City / Mouri, Koto City / Morishita, Koto City / Monzen-Nakacho, Koto City / Yumenoshima, Koto City / Wakasu, Koto City
・Trust Kakeru Koumuten for exterior wall painting in Koto, Tokyo!
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・Trust Kakeru Koumuten for exterior renovations in Koto, Tokyo!
・Kakeru Koumuten Co., Ltd. project achievements
・Kakeru Koumuten Co., Ltd. aftercare services
・Kakeru Koumuten Co., Ltd. service menu and price list
・Kakeru Koumuten Co., Ltd. staff blog and announcements
・Explaining the importance of getting multiple estimates and points to compare!
・Top 12 solar power manufacturers! Features and tips for selection!
・What are the installation costs for solar power? Comprehensive tips to reduce costs!
・What are the best locations for installing solar power? Points for selecting installation sites!
・Here for solar power 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!
