Leave Your Solar Panel Installation Work in Koto City, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and storage battery installation in
Koto City, Tokyo,
trust Kakeru Koumuten!
Kakeru Koumuten is a specialized exterior renovation company based in Aoba Ward, Yokohama City.
As a company strong in roofing work, we are entrusted withsolar panel and storage battery installations considering roofing and waterproofing!
“How to Choose a Solar Panel Contractor in Koto City”
“About the Costs of Solar Panel and Storage Battery Installation”
“About Subsidies Available 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 obtainingcomparative estimates from about three companies!
Table of Contents (Tap to Expand)
- 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 Storage Battery Installation
- Breakdown of Installation Capacity, Equipment, and Construction Costs
- Self-Estimate and Profit Simulation for Solar Power Generation
- Customer Testimonials
- Case Studies of Solar Panel Installations
- How to Choose a Solar Panel Installation Company in 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 Storage Battery Installation in Koto City
- If You’re Looking for a Solar Panel Installation Company 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
Here are the reasons 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.” Additionally,
“We have unique strengths in solar panel installation that cannot be replicated by other companies,” which has garnered us many satisfied customers.
We would greatly appreciate it if you could compare our estimates with those of other companies.
Because we are confident, we welcome estimates from any number of companies!
1. We Also Handle Exterior Renovations Besides Solar Panel Installation!
Troubles 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 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 troubles after solar panel installation!
2.Equipment Specialized in Exterior Renovation
Kakeru Koumuten Co., Ltd. has organized the following warehouses and material storage areas to provide solar work and exterior renovations at low cost and high quality.
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 and can assemble scaffolding ourselves.
By conducting scaffolding work with our own scaffolding team instead of outsourcing, we can also reduce scaffolding construction costs.
We have scaffolding materials for approximately 50 single-family homes!
Even in Koto Ward, where low-lying areas near water are widespread, our in-house 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 canrespond quickly in emergencies!
In-house sorting and transportation of waste materials
The installation of solar panels often involves roofing work, generating various waste materials such as paint, wood, and metal.
By sorting and recycling waste materials, we can significantly cut down on 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 roofing renovations at reduced costs.
Additionally, one representative will handle everything from the estimate to project completion.
Since the person in charge does not change, whether it be sales or construction management, smooth communication is possible.
We can perform consistent in-house work from temporary scaffolding installation to exterior wall painting and roofing renovations!
4. Various Permits and Skilled Workers
We have obtained construction business permits and permits for industrial waste collection and transportation!
We also have nationally certified sheet metal and painting technicians on staff, giving us confidence in our construction techniques.
We are capable of handling 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 roof remodeling is performed. The workmanship warranty is separate from the manufacturer’s product warranty, and the coverage and conditions vary based on the warranty details.)
Aftercare maintenance is available annually, and we send out notification DM each 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 services 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 method changes depending on the shape and slope of the roof, we regularly conduct technical improvement education so that each staff member can respond to various cases.
8. Creation of Easy-to-Understand Materials and Simulations
At Kakeru Koumuten Co., Ltd., in addition to “estimates”, “layout diagrams”, and “power generation simulations”, we also provide a “solar panel installation guidebook” and a “profit and loss simulation” that takes into account loan interest rates and electricity costs.
The profit and loss simulation can be created for projected cumulative profits and losses over 20 to 30 years.
Even customers who are not familiar with solar panel installations can easily understand the important points and disadvantages, as we compile this information into clear materials!
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 Co., Ltd., which specializes 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 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 power generation. We will create a layout diagram from the drawings and the site, and you can confirm this with the power generation simulation. |
| 4. Shape of the roof and available installation area | The number of panels that can be installed (installation capacity) is determined by the shape and size of the roof. The number of panels that can be installed varies depending on their size, so we will compare based on the total output of the roof. |
| 5. Method of securing and waterproofing details | We will confirm whether the method involves drilling holes in the roofing material or securing it with brackets. The method of securing varies by technique, so please check the waterproofing treatment for the fastening parts during 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, switching to lighter roofing materials may also be an option if necessary. |
| 7. Location of equipment installation and wiring | We will check the installation locations for the power conditioner and storage batteries, as well as the wiring route to the distribution board. The length of the wiring also affects 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 of fixed parts, cracks or deterioration of slate, condition of the substrate. If deterioration is advanced, consider roof overlay (cover method) or replacement first. |
| Tile Roof | Fixed with brackets and methods suitable for the type of tile (even methods that do not drill holes in the tiles will fix to the substrate) | Type and condition of tiles, substrate, load-bearing capacity. Depending on the investigation results, there may be a method to replace with lightweight roofing material 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) | Compatibility of roof material and brackets, installation conditions from the roof material manufacturer. If compatible, a method that does 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 plan to renovate the roof 10 to 20 years after installation, there will be additional costs for the removal and reinstallation of solar panels. If the roof is deteriorating, renovating to a highly durable roofing material before installation may help reduce costs in the long run.
Kakeru Koumuten Co., Ltd. specializes in roofing work and can also handle the removal and reinstallation of solar panels 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 you may be eligible for programs from the “National Government,” “Tokyo Metropolitan Government,” and “Koto City”.
The following information is based on the official pages of each program as of October 7, 2026. The application status may change depending on the budget and application 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 “Fiscal Year 2026 Home Solar Power Generation Promotion Project” (Cool Net Tokyo) | New installation of certified solar modules in residential properties or their premises within the city, 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 “Fiscal Year 2026 Home Battery Storage Promotion Project” (Cool Net Tokyo) | New installation of battery storage in residential properties within the city, and must be SII registered equipment. This project is intended for simultaneous installation with solar power, but applications can be made for battery storage alone. Pre-applications after October 1, 2026 will only be eligible for SII registered products for fiscal year 2026. | Battery storage package: 100,000 JPY/kWh (maximum 1,200,000 JPY per household) 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 |
| Koto Ward “Fiscal Year 2026 Global Warming Prevention Equipment Installation Subsidy (for Individual Homes)” | Owners or prospective owners of residential properties within the ward, and residents of rental properties (with owner consent) are eligible. Solar power requires a power purchase agreement with the utility company, and battery storage must be SII registered equipment. Application must be made before construction begins. | Solar power generation: 50,000 JPY per kW (maximum 200,000 JPY) Battery storage: 10,000 JPY per kWh (maximum 100,000 JPY) If applying for both solar power and battery storage simultaneously: Solar power is 60,000 JPY per kW (maximum 240,000 JPY), battery storage 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 ward’s materials, so please check with the ward office. |
| National Government “DR Home Battery Storage Project” (Supplementary Budget for Fiscal Year 2025) | New installation of home battery storage systems that can be utilized for DR (demand response) with registered products. | Calculated based on an initial effective capacity of 34,500 JPY per kWh (subsidy rate within 3/10; maximum 600,000 JPY per application). | The budget was reached on May 29, 2026, and the public recruitment has ended (applications are currently not possible). |
| National Government “Mirai Eco Housing 2026 Project” (Renovation) | Battery storage is one of the eligible facilities, but it must be combined with essential renovations such as insulation improvements for windows (openings) and the building structure; applications cannot be made for battery storage installation alone. Solar panels are not included as eligible facilities. | 蓄電池：96,000 JPY/戸 | 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 in Koto City, applications must be submitted before construction starts (applications after construction has begun will not be accepted). If construction is started beforehand, it will be excluded from eligibility, and applying does not guarantee that the subsidy will be granted. Procedures and eligibility for each system may differ, so please confirm before contracting or starting construction.
Kakeru Koumuten Co., Ltd. will guide you on the eligibility conditions for each system after confirming them.
Tokyo “Reiwa Year 8 Household Solar Power Introduction Promotion Project”
In Tokyo, subsidies are provided for those installing solar power systems in residential homes through Cool Net Tokyo. The target is systems using certified solar modules installed newly in residential homes or on their premises, with a capacity of less than 50kW. A pre-application before installation is required.
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 supplementary items such as installation of mounting frames, waterproofing work, and renovation defect insurance. The pre-application period is from May 29, 2026, and the application for grants and performance reports is from June 30, 2026, to March 30, 2029. For details on eligible equipment and conditions, as well as the budget status, please check the official page.
👉 Cool Net Tokyo | Official page for solar power is here
Tokyo “Reiwa Year 8 Household Storage Battery Introduction Promotion Project”
Tokyo is also providing subsidies for newly installed storage batteries in residential homes. The subsidy amount is 100,000 JPY per kWh for storage battery packages (maximum 1,200,000 JPY/戸), and 60,000 JPY per kWh for additional storage battery units (maximum 720,000 JPY/戸), 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 Year 8 SII registered product list will be eligible. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries alone. The application for grants and performance reports has been accepted since June 30, 2026.
👉 Cool Net Tokyo | Official page for storage batteries is here
Koto City “Reiwa Year 8 Global Warming Prevention Equipment Installation Subsidy (for Individual Homes)”
Koto City is implementing the “Global Warming Prevention Equipment Installation Subsidy” to subsidize part of the costs for those installing solar power systems or storage batteries in homes within the district. Applications must be submitted before construction starts, and applications after construction has begun 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). When applying for both solar power and storage batteries simultaneously, the amount 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 applications to be submitted by the end of February whenever possible. Please check with the ward office regarding the budget situation and the possibility of combining with other subsidies.
👉 Koto Ward Official Page (for individual residences and collective housing) here
National Subsidy “DR Home Storage Battery Project (Support Project for Home Storage Systems for DR Resource Introduction)”
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), and in the fiscal year 2025 supplementary budget, the subsidy amount was 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 fiscal year 2025 supplementary budget reached its application budget 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 possible, so please check the official site for future public recruitment.
Additionally, there are currently no subsidies confirmed for the installation of solar panels for existing homes.
👉 Official Site for DR Home Storage Battery Project here
Solar Panel Installation & Storage Battery Installation Price List
⇧Service Menu | Click here for costs related to Solar Panel Removal and Hot Water Heater Dismantling
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and storage batteries should be confirmed by separating them into “Equipment Costs (Device Costs)” and “Construction Costs”.
Even for the same “Solar Panel Installation Set,” 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, expressed 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 the costs for solar panels as approximately 800,000 JPY to 1,200,000 JPY for 3-5 kW and 1,200,000 JPY to 1,900,000 JPY 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 just by looking at the amounts. Please check if the following items are clearly stated in the estimates from each company!
| 1. Solar Panels | Check if the manufacturer, model number, output per panel (W), number of panels, and total installation capacity (kW) are listed. |
| 2. Power Conditioner | Check the manufacturer, model number, capacity, number of units, and installation location (indoor/outdoor). Also confirm whether it is a type that controls the battery together. |
| 3. Storage Battery | Check the manufacturer, model number, capacity (kWh), range of use during power outages (entire house or specific circuits), and installation location. |
| 4. Mounting Frame and Hardware | Check the names of the hardware suitable for the roofing material and the method of securing it (whether it involves drilling holes or using clamps). |
| 5. Wiring and Electrical Work | Check the wiring route and length, work around the distribution board, and whether there is a monitor to check the power generation amount. |
| 6. Roof Reinforcement and Waterproofing | Check the details of waterproofing treatment at the fixed parts and whether necessary roof repairs and substrate reinforcements are included. |
| 7. Applications | Check how much support is included for applications to the power company, certification applications for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Check the scope and quantity of scaffolding. If roof work and exterior painting are done simultaneously, confirm that the same scope and quantity are not counted twice. |
| 9. Removal and Disposal | Check if the removal of existing solar thermal water heaters and old panels, as well as disposal costs for waste materials, are included. |
| 10. Tax Classification and Warranty | Check whether the price is tax-inclusive or tax-exclusive, conditions under which additional costs may arise, and the details and duration of manufacturer and workmanship warranties. |
If the capacity differs, both the price and power generation amount will change. Kakeru Koumuten Co., Ltd. warmly welcomes comparative estimates, 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 above simulator,
you can get an approximate estimate and a profit simulation for up to 30 years!
If you know the total installation capacity of solar panels on the roof and the capacity of the storage battery, you can get an 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)!
Installation Examples of Solar Panels
| Work Details |
| Solar Panel Installation Battery Installation |
| Existing Roofing Material |
| Horizontal Metal Roof (Super Galtect) |
| Installation Capacity |
| Solar Panel: 4.3kW Battery: 5kWh |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing 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 grant being provided, the actual burden amount is approximately 1,000,000 JPY Estimated recovery period for construction costs: about 8 to 9 years (self-consumption) *The grant amount and recovery estimate are based on the system and calculations at the time of construction, and may differ under the current system. |
| Construction Period |
| Approximately 3 days |
| Completion Month |
| April 2025 |
| Inquiry Details |
| I am considering the installation of solar panels and storage batteries. I heard that grants are available, and I would like to know how much 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 when solar panels are placed on the roof.
Since we can also determine the installation capacity, it allows for power generation simulations and financial simulations.
We have 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 services
● 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.
Have knowledge not only about solar panels but also about roofs
Defective installation of solar panels can 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
・Installing solar panels on a severely deteriorated roof, leading to leaks
・Installing solar panels on a roof with a short lifespan, requiring reinstallation of the solar panels within a few years
・Misjudging the type of waterproofing and applying incorrect treatment, resulting in 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 presence of warranties and aftercare services
When choosing a solar installation contractor, let’s confirm the presence of warranties. It is important to check not only the duration of the warranty but also the coverage, exclusions, and cost conditions.
While the solar panels and battery storage units come with manufacturer warranties, it is also essential to check for the presence of 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 respond under the warranty, provided it is within the warranty period and conditions.
Additionally, some contractors offer after-sales service separate from warranties, so be sure to check if the contractor you are considering has after-sales service.
Changes or damage on the roof may occur in areas that are not visible, so there is a possibility that customers may not notice them.
By conducting inspections during after-sales maintenance, we can easily detect abnormalities early and prevent major repairs or breakdowns!
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, a roof renovation may be required to provide the warranty.)
We also conduct after-sales maintenance and send out DM every year!
Please check the DM, and if you wish, we will visit you for after-sales maintenance!
Obtain estimates from multiple contractors (3 companies is 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-sales 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-sales services”
and make a detailed 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 and equipment/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 submitted by the contractor, as well as systems that require prior applications before installation, so it is reassuring to have a contractor that supports the preparation of necessary documents and the flow of procedures.
Complete the procedures specified for each system (for Tokyo’s subsidy, a prior application before installation is required; for Koto Ward’s grant, an application before the start of construction is required) 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 varies 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 purchased from the utility company through self-consumption of generated power!
As electricity prices rise, the ability to cover your consumption with solar power becomes increasingly attractive!
If you plan to use the generated power 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 fiscal year 2026. After the fifth year, it is often more advantageous to use it at home (self-consumption), making the combination with a storage battery a viable option.
👉 For purchase prices, periods, etc., 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 criteria, you may be able to utilize subsidies!
Reducing the actual burden through subsidies is a significant advantage!
In the case of Koto Ward, in addition to national and Tokyo metropolitan programs, there may be eligibility 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 has low carbon dioxide emissions and can reduce 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 a good method of power generation for the environment. (However, devices like power conditioners do have operational noise.)
Advantage 4 Expect Heat Shielding Effect!!
By installing the panels on the roof or rooftop, they block direct sunlight from hitting the roof.
Especially in summer, it can help reduce the temperature rise of the roof, so heat shielding 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 capability, 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 can be incurred
A particularly overlooked maintenance cost is for the roof where the solar panels are installed.
If you perform a roof renovation 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 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 ask for a simulation that considers maintenance costs before introducing solar panels!
Point 2 The risk of leaks increases depending on the roofing material
The method of securing slate roofs and tile roofs varies depending on the construction method, but when securing materials and substrates with screws or similar fasteners, waterproofing 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 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 specifically for horizontal metal roofs
Note 3: The roof will become heavier
Since solar panels will be installed, 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.
It is not simply a matter of “this manufacturer has the best solar panels”; it is important to choose solar panels that are suitable for your life plan and building!
Here are some points to consider when comparing solar panels!
How to Choose 1: Compare by Overall Roof Output
When installing solar panels on the roof, it is important to know how much electricity can be generated in a limited area, and the more electricity generated, the better!
Solar panels come in various sizes depending on the manufacturer, and their outputs differ.
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 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 may lead to different installable quantities on the same roof due to the size difference.
400W×15 panels = 6kW (total output of the roof)
350W×20 panels = 7kW (total output of the roof)
As shown above, even if the output of one panel is lower, the total output of the roof may be higher!
It is important to consider the overall output of the roof rather than the output of a single panel!
*The above is a calculation of total output (kW). The actual power generation (kWh) will vary depending on conditions such as roof orientation, slope, and shading.
How to Choose 2: Compare by Degradation Rate of Solar Panels
Solar panels have a degradation rate, and their output gradually decreases over 10 and 20 years.
The degree of output reduction after long-term use varies by product. The manufacturer’s output warranty values are standard figures for guarantees and do not indicate the actual degradation rate or power generation amount.
Choosing solar panels while considering both initial output and degradation rate will lead to a decision without regrets!
How to Choose 3: Compare by Warranty Years
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty years vary by manufacturer.
Regarding output warranties, some manufacturers offer a 30-year warranty while others provide a 10-year warranty, so it varies widely!
A longer warranty is always better, so be sure to check the warranty years and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar 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 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 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 (registered products for 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 construction begins. 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 are required before construction. Tokyo’s subsidies require pre-application before installation, and Koto Ward’s grants require application before construction begins; if you install first, you will be ineligible. Procedures vary by program.
Since the order of procedures differs by program, please confirm before signing a contract or starting construction.
Can solar panels be installed on slate roofs? I’m worried about leaks.
It is possible to install on slate roofs, but it is necessary to check the condition of the roofing material and substrate beforehand. The method of securing varies by 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, there will be additional costs for removing and reinstalling solar panels. If the remaining lifespan of the roof is short, it may be more cost-effective to renovate with durable roofing materials before installation.
Please consult us on how to proceed with the installation after checking the condition of the roof during the 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 intended for simultaneous installation with solar panels, but you can also apply for the storage battery alone. You can compare “solar panels only” and “solar panels + storage battery” through a financial simulation.
How many kW can be installed on my roof? Is it okay for north-facing roofs or roofs with shadows?
The capacity that can be installed varies depending on the shape, orientation, and size of the roof. At Kakeru Koumuten Co., Ltd., we create a layout diagram from the drawings and site survey, and provide you with the installation capacity and power generation simulation.
In Koto Ward, the appearance of the city varies from the waterfront area to residential areas, and the way shadows are cast by neighboring houses and surrounding buildings differs from one house to another. You can check the expected power generation through the power generation simulation.
How long will the construction period be?
For 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 and the shape and installation capacity of the roof.
Additionally, there will be a separate period for applying for subsidies and to the power company, so please consult us as soon as possible.
What is the current selling price (FIT)?
For residential use (under 10 kW), from the certifications after October 2025, the first 4 years will be 24 yen/kWh, and from the 5th to the 10th year it will be 8.3 yen/kWh, with the same prices applying for the 2026 fiscal year.
The idea is to recover initial costs more quickly in the first 4 years and then focus on self-consumption. Kakeru Koumuten Co., Ltd. provides a financial simulation that considers 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 notifications and visits for inspections upon request from customers. We can also clean solar panels with a special brush if the power generation decreases due to dirt.
The roof is a part 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, it is possible. 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 company in Koto City, please consult Kakeru Koumuten
Our company handles a wide range of exterior renovations, including solar panels, roof work, and exterior wall work in Koto City, Tokyo.
We have received requests from many customers, including renovation companies and real estate agencies, who have contacted us!
Kakeru Koumuten promises “high-quality renovations at low costs”, and we have received positive feedback from numerous customers.
We continue to update our construction performance each year, and we will strive to improve quality to satisfy even more customers in the future.
Our company can perform not only roof overlay work and re-roofing but also partial roof repairs, exterior painting, and exterior wall cover methods, all with our own team.
We are also happy to assist with 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 the best solutions for your specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s position and propose the optimal construction plan!
We are confident that we will not lose 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 Koto City, Tokyo, and Points for Solar Work
Koto City, 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 City introduces its area as 42.99 km2, featuring many neighborhoods such as Aomi, Ariake, Toyosu, Kameido, and Fukagawa.
We have summarized the points to consider when installing solar panels and storage batteries in Koto City’s residential environment below. (Tap to open)
View the characteristics of Koto City, Tokyo, and points for solar construction
■ In areas with low-lying waterfronts, confirm installation locations for storage batteries and power conditioners with flood risk in mind
Koto City is surrounded by the Sumida River, Arakawa River, and Tokyo Bay, with many rivers and canals within the district. When deciding on the installation location for storage batteries and power conditioners, it is advisable to check the flood risk for your residence on a hazard map and consider the height and position of the installation for peace of mind.
■ Consider the effects of sea breezes in areas close to Tokyo Bay, rivers, and canals
In locations near Tokyo Bay, rivers, and canals, you may be affected by winds containing salt. It is important to regularly check the condition of the metal parts of panels, frames, and outdoor equipment even after installation.
■ Tokyo’s annual sunshine duration is approximately 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), Tokyo has an annual sunshine duration of about 1,927 hours.
Since power generation varies by season, it is essential to conduct annual power generation simulations and choose the capacity of storage batteries to match the times of high electricity usage.
■ In areas with varying urban landscapes from the bay area to Fukagawa and Joto, check for shadows from neighboring houses
Koto City features different 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 property to another. Kakeru Koumuten Co., Ltd. creates layout diagrams based on blueprints and the actual site conditions, allowing you to confirm 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 Co., Ltd. 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 homes 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 City
The subsidy from Tokyo requires prior application to Cool Net Tokyo, while Koto City’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 construction and solar projects in Koto City, 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 City, Tokyo
Kakeru Koumuten Co., Ltd. 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 / Shinkiba, Koto City / Shinsuna, Koto City / Sumiyoshi, Koto City / Sengoku, Koto City / Chida, Koto City / Takahashi, Koto City / Tatsumi, Koto City / Chuo Breakwater, Koto City / Toyo, Koto City / Takanawa, Koto City / Hirano, Koto City / Fukagawa, Koto City / Fukuzumi, Koto City / Fuyuki, Koto City / Koishiba, Koto City / Botan, Koto City / Minasuna, 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. 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 comparison 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!
・Here for solar power generation estimates!
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contact Kakeru Koumuten Co., Ltd.
Kakeru Koumuten is a young company whose team is, on average, in their late twenties, but our skills are second to none.
Our greatest strength is that we handle scaffolding, roofing and painting entirely in-house. In an industry where these tasks are usually divided among contractors, our complete service simplifies project management and helps keep costs down. Above all, if a problem arises, we respond promptly.
We proudly describe ourselves as the youngest and most helpful renovation company in Kanagawa!
