Leave Your Solar Panel Installation Work in Ota City, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and storage battery installation in
Ota City, Tokyo,
Kakeru Koumuten is at your service!
Kakeru Koumuten is a specialized exterior renovation company headquartered in Aoba Ward, Yokohama City.
As a company strong in roofing work, we are entrusted with solar panel and storage battery installations considering roofing and waterproofing!
“How to Choose a Solar Panel Contractor in Ota City”
“Costs for Solar Panel and Storage Battery Installation”
“Subsidies Available for Solar System Installation in Ota City”
We will also explain the above three points!
Installing solar panels carries the risk of “water leaks” and other troubles.
To ensure a satisfactory solar panel installation, we recommend obtaining quotes from about three companies!
Table of Contents (tap to open/close)
- Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Ota City, Tokyo
- Roof Inspection Before Installing Solar Panels
- Subsidies and Grants Available in Ota 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 Installer in Ota 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 Ota City
- If You Are Looking for a Solar Panel Installer in Ota City, Contact Kakeru Koumuten
- Characteristics of Ota City, Tokyo and Key Points for Solar Work
- Service Area in Ota City, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Ota City, Tokyo
Regarding why our company is entrusted with solar panel installation by customers in Ota City, Tokyo,
One reason is that “Kakeru Koumuten serves Kanagawa and Tokyo areas”,
and we have “strengths in solar panel installation that cannot be imitated by other companies”, which has received high praise from many customers.
so we would appreciate it if you could compare our estimates with those of other companies.
Because we are confident, we welcome estimates from any number of companies!
1. We Also Handle Exterior Renovations Beyond Solar Panel Installation!
Troubles such as leaks that occur with 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 be knowledgeable 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.Facilities Specialized in Exterior Renovation
Kakeru Koumuten Co., Ltd. has organized the following warehouses and material storage areas to provide low-cost, high-quality solar work and exterior renovations.
We have established five bases centered around Yokohama City, Kanagawa Prefecture for material storage and showrooms.
In-house Ownership of Scaffolding Materials
To ensure safety during work on the roof, we own the necessary scaffolding materials for temporary scaffolding based on construction conditions, allowing us to assemble scaffolding ourselves.
By performing scaffolding work with our own scaffolding team instead of outsourcing, we can also cut costs on scaffolding work.
We have scaffolding materials for approximately 50 single-family homes!
Even in Ota City, where the terrain varies from residential areas on plateaus to low-lying areas along the Tamagawa River and coastal regions, our in-house scaffolding team plans 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, we canpurchase materials at a lower cost!
Additionally, since we always have roofing materials in stock, we can provideswift responses even in emergencies!
Sorting and transporting waste materials in-house
The installation of solar panels often involves roofing work, generating various waste materials such as paint, wood, and metal.
By sorting and recycling waste materials, we can significantly cut 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 illustrate the structure, allowing for detailed explanations!
3.Complete In-House Construction
One of Kakeru Koumuten’s major strengths is 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 remodeling.
Additionally, one representative will assist you from the estimate to the completion of the work.
Since the person in charge does not change, whether it is the sales representative or the construction management representative, smooth communication is possible.
We can provide consistent in-house construction from temporary scaffolding installation to exterior wall painting and roof remodeling!
4. Various Permits and Skilled Workers
We have obtained construction industry permits and permits for industrial waste collection and transportation!
We also have nationally certified sheet metal workers and painting technicians, and we are confident in our construction skills.
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 renovation is performed. The workmanship warranty is separate from the manufacturer’s product warranty, and the scope 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 places, we can utilize a drone for inspection!
During leakage investigations, we can also conduct inspections using a thermal imaging camera.
If the power generation of the solar panels decreases due to dirt, we can also provide cleaning with a specialized brush.
We will respond according to the customer’s wishes.
7. Human Resource Development
To improve skills, we create various roof models and conduct practical training.
Since the construction methods vary depending on the shape and slope of the roof, we regularly provide technical training so that each staff member can handle various cases.
8. Creation of Clear Materials and Simulations
At Kakeru Koumuten Co., Ltd., in addition to “estimates”, “layout diagrams”, and “power generation simulations”, we also provide a “solar installation guidebook” and a “financial simulation” that takes into account loan interest rates and electricity costs.
The financial simulation can project cumulative income and expenses over 20 to 30 years.
We prepare easy-to-understand materials that include important points and disadvantages for customers who may not be familiar with solar installations!
We encourage you to obtain comparative estimates and review plans from other companies!
Roof Inspection Before Installing Solar Panels
Once solar panels are installed, they will remain on the roof for 20 to 30 years.
Confirming whether it is safe to install them directly on the current roof 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 based on the drawings and the site, and you can verify it with the power generation simulation. |
| 4. Shape of the roof and installable 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 for fastening or using brackets to secure the roofing material. The fastening method varies by technique, so please check the waterproofing treatment of 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 be an option if necessary. |
| 7. Location of equipment installation 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 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) | Waterproof treatment of fixing parts, cracks or deterioration of slate, condition of the substrate. If deterioration is advanced, consider roof overlay (cover method) or replacement first. |
| Tile Roof | Fixed with brackets and methods suitable for the type of tile (even methods that do not drill holes in the tiles will secure to the substrate) | Type and condition of tiles, substrate, load-bearing capacity. Depending on the investigation results, there may be methods to replace with lightweight roofing materials before installation. |
| Metal Roof (Horizontal and Vertical) | Fixed with catch-type brackets that grip the roof material (depends on the combination of roof material and brackets) | Whether the roof material and brackets are compatible, installation conditions from the roof material manufacturer. If compatible, methods that do not drill holes may be available. |
| Flat Roof / Rooftop | Fixed by installing a frame | Type and deterioration status of the waterproof layer, waterproofing around the frame. Consider in conjunction with the timing of waterproofing work. |
If you carry out roof renovation 10 to 20 years after installation, additional costs for removing and reinstalling solar panels will apply. If the roof is deteriorating, renovating to a highly durable roofing material before installation may help reduce costs in the long run.
Kakeru Koumuten Co., Ltd. specializes in roofing work and can also handle the removal and reinstallation of solar panels in-house, so please consult us according to the condition of your roof!
▶ Click here for roof renovation in Ota City, Tokyo
Potential Subsidies and Grants in Ota City, Tokyo
When introducing solar panels or storage batteries in Ota City, Tokyo, there is a possibility of being eligible for programs from the “National Government,” “Tokyo Metropolitan Government,” and “Ota City”.
The following information is based on the official pages of each program as of October 6, 2026. The application status may change depending on the budget and recruitment period, so please check the latest information before contracting or starting work.
Eligibility Conditions and Application Timing for Subsidy Programs
| System | Main Eligibility Conditions | Subsidy Amount | Application Period & Status |
|---|---|---|---|
| Tokyo Metropolitan Government “Reiwa 8 Year Household Solar Power Generation Promotion Project” (Cool Net Tokyo) | A system under 50kW with newly installed certified solar modules on residential properties within the Tokyo area. Pre-application before installation is required. | Existing homes: 150,000 JPY/kW for 3.75kW or less (maximum 450,000 JPY), 120,000 JPY/kW for over 3.75kW New homes: 120,000 JPY/kW for 3.6kW or less (maximum 360,000 JPY), 100,000 JPY/kW for over 3.6kW (Additional costs for mounting frames, waterproofing work, and renovation defect insurance, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 to March 30, 2029 |
| Tokyo Metropolitan Government “Reiwa 8 Year Household Storage Battery Promotion Project” (Cool Net Tokyo) | New installation of storage batteries in residential properties within Tokyo, with SII registered equipment. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries alone. Pre-applications after October 1, 2026 will only be for SII registered products for Reiwa 8. | Storage battery package: 100,000 JPY/kWh (maximum 1,200,000 JPY per household) Storage battery unit expansion: 60,000 JPY/kWh (maximum 720,000 JPY per household) (Additional incentives for participation in DR demonstrations, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 |
| Ota City “Housing Renovation Subsidy Project” Reiwa 8 Year | Residents with a registered address in Ota City from January 1, 2026, to the application date. Installation of solar power generation and storage batteries is included in Category A work. Construction must be performed by small and medium-sized enterprises with headquarters in the city. | 10% of the eligible amount (maximum 200,000 JPY) If used in conjunction with other systems, 5% (maximum 100,000 JPY) |
Pre-application: From April 1, 2026 to January 29, 2027 Main application: By 5 PM on March 19, 2027 Ends as soon as the budget is exhausted. |
| National “DR Household Storage Battery Project” (Reiwa 7 Year Supplement) | New installation of household storage systems using registered products that can be utilized for DR (demand response). | 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 accepted). |
| National “Mirai Eco Housing 2026 Project” (Renovation) | Storage batteries are one of the eligible facilities, but they must be combined with essential work such as insulation renovation of windows (openings) and structures; applications cannot be made for storage battery installation alone. Solar panels are not included as eligible facilities. | Storage battery: 96,000 JPY per household | As soon as the budget limit is reached, it will end. Please check the official website for the application status. |
In Tokyo, a pre-application before installation is required for subsidies, and the process involves submitting a grant application and performance report after the completion of the work. The subsidy program in Ota City requires construction by small and medium-sized enterprises with headquarters in the city (our company is headquartered in Aoba Ward, Yokohama City, so we do not qualify for this subsidy program). It is not guaranteed that an application will be granted, and the procedures differ by program, so please confirm before contracting and starting work.
At Kakeru Koumuten, we will guide you on the eligibility conditions based on the Tokyo subsidy program.
Tokyo “Reiwa 8 Year Household Solar Power Generation Promotion Project”
In Tokyo, subsidies are provided for those installing solar power generation systems in residential homes through Cool Net Tokyo. The target is systems using certified solar cell modules that are newly installed 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 yen/kW for up to 3.75kW (maximum 450,000 yen), and 120,000 yen/kW for systems exceeding 3.75kW. Additionally, there are extra items such as installation of mounting frames, waterproofing work, and renovation defect insurance. The pre-application period is from May 29, 2026, and the grant application and performance report can be submitted from June 30, 2026, to March 30, 2029. Please check the official page for details on eligible equipment, conditions, and budget status.
👉 Cool Net Tokyo | Official page for solar power generation is here
Tokyo “Reiwa 8 Year Household Storage Battery Promotion Project”
Tokyo is also providing subsidies for newly installed storage batteries in residential homes. The subsidy amount is 100,000 yen per kWh for storage battery packages (maximum 1,200,000 yen per household), and for additional storage battery units, it is 60,000 yen per kWh (maximum 720,000 yen per household), with additional amounts for participation in DR demonstrations.
The target is equipment registered with SII (Environmental Collaboration Initiative). If you apply for pre-application after October 1, 2026, only equipment listed in the Reiwa 8 Year SII registered product list will be eligible. This project is intended for simultaneous installation with solar power, but applications can also be made for storage batteries alone. The acceptance of grant applications and performance reports has started from June 30, 2026.
👉 Cool Net Tokyo | Official page for storage batteries is here
Ota City “Housing Renovation Subsidy Project” Reiwa 8 Year
Ota City is implementing a subsidy program for housing renovation work within the city, and the installation of solar power generation systems and storage battery systems is included as A work (for a decarbonized society). The subsidy rate is 10% of the eligible subsidy amount (maximum 200,000 yen), and if used in conjunction with other programs, it will be 5% (maximum 100,000 yen).
The target audience includes residents of Ota City who have a resident registration as of January 1, 2026, and until the application date, and the construction is limited to small and medium-sized businesses headquartered within the city. Pre-registration is available until January 29, 2027, and the main application is accepted until March 19, 2027, at 5 PM, but will end as soon as the budget is exhausted. According to the official page of the city, as of September 2026, the planned execution rate for pre-registrations against the budget (approximately 116 million yen) is about 50%. Additionally, since our company is headquartered in Aoba Ward, Yokohama City, we do not qualify as a contractor for this subsidy project.
👉 Click here for the official Ota City page
National Subsidy “DR Home Battery Project (Support Project for the Introduction of Home Storage Systems for DR Resources)”
The national government has been implementing the “DR Home Battery Project” to support the installation of home storage batteries.
This program targets individuals who are newly introducing registered storage systems that can be utilized for demand response (DR), and for the fiscal year 2025 supplementary budget, the subsidy amount is determined based on a standard amount of 34,500 yen per initial effective capacity of 1 kWh, with a subsidy rate of up to 30% and a maximum of 600,000 yen per application. There are also 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 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.
👉 Click here for the official DR Home Battery Project site
Solar Panel Installation & 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 (Equipment Price)” 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 (kilowatt). Storage batteries are compared based on the amount of electricity they can store, measured in kWh (kilowatt-hour).
The amount of kW that can be installed on a roof varies for each house based on the roof’s shape, orientation, and size. At Kakeru Koumuten, we create layout diagrams from blueprints and on-site surveys to present the installation capacity.
On our pricing page, we list solar panel costs as approximately 800,000 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 may 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 Confirm 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) should be specified. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, installation location (indoor/outdoor). Also check if it is a type that controls the battery together. |
| 3. Storage Battery | Manufacturer, model number, capacity (kWh), range usable during a power outage (entire house or specific circuits), installation location. |
| 4. Mounting Frame and Hardware | Name of the hardware suitable for the roofing material and the method of securing it (whether it is a method that drills holes or a method that grips 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 the fixing points, whether necessary roof repairs and substrate reinforcements are included. |
| 7. Application | How much support is included for applications to the power company, certification applications for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Scope and quantity of scaffolding. If roof work and exterior painting are done simultaneously, check that the same scope and quantity are not counted twice. |
| 9. Removal and Disposal | Whether the removal of existing solar water heaters or old panels and disposal costs for waste materials are included. |
| 10. Tax Classification and Warranty | Whether it is tax-inclusive or tax-exclusive, conditions under which additional costs may arise, details and duration of manufacturer warranty and workmanship warranty. |
If the capacity is different, both the price and power generation will change. Kakeru Koumuten Co., Ltd. warmly welcomes competitive 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 simulator above,
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 conditions such as electricity rates, self-consumption ratios, selling prices, and costs for equipment inspection and 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 Installation
| Construction Details |
| Solar Panel Installation Battery Installation |
| Existing Roofing Material |
| Horizontal Metal Roof (Super Galtect) |
| Installation Capacity |
| Solar Panel: 4.3kW Battery: 5kWh |
| Base Mounting Hardware Used |
| Niigata Manufactured / Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Arrangement |
| Fixed by gripping 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 there are grants available, and I would like to know how much can be provided. |
Our Proposal
We visited to provide an estimate and created a layout diagram for the solar panels 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 grants, so we explained it to the customer along with the estimate!
How to Choose a Solar Panel Installation Contractor in Ota City, Tokyo
There are many solar panel installation contractors available in Ota City, Tokyo, and you may be unsure which contractor to choose.
For this reason,when requesting solar panel installation or battery storage installation work, let’s confirm 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 confirmation 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 checks on roofs and waterproofing
・Solar panels installed on a severely deteriorated roof causing leaks
・Solar panels installed on a roof with a short lifespan, requiring remodeling to detach and reattach 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 Check Before Installing Solar Panels” in this article
Confirm the presence of warranties and aftercare maintenance
When choosing a solar installation contractor, 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, also check for the presence of a workmanship warranty in case leaks occur after installation!
For contractors that offer a workmanship warranty, if leaks occur after installation, they may be able to address the issue under the warranty, as long as it falls 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 prevent significant repairs or failures by detecting abnormalities early!
Kakeru Koumuten Co., Ltd. provides a leak warranty as part of the workmanship warranty for solar panel installations. (The warranty for solar panel installations is 10 years, and depending on the condition of the roof before installation, we may not be able to provide a warranty unless roof renovations are performed.)
We also conduct after-sales maintenance, and we send out DM every year!
After checking the DM, if you wish, we will visit you for after-sales maintenance!
Obtain estimates from multiple contractors (3 companies as a guideline)
When requesting solar panel installation, be sure to obtain estimates from multiple contractors.
Even for the same manufacturer and the same construction content, costs may vary, as well as warranties and after-sales services.
Additionally, obtaining multiple estimates makes it easier to negotiate prices.
To request services from your preferred contractor at a lower price, we recommend obtaining estimates from multiple contractors.
When comparing estimates, please check the following:
“Check the items in the estimate”
“Type of solar panels”
“Warranties and after-sales services”
Make sure to compare these details carefully! If the quality of the auxiliary materials is low or if steps are skipped, costs can be reduced, so avoid making judgments based solely on price!
▶ Go to “Breakdown of Installation Capacity and Equipment/Construction Costs” in this article
Confirm whether 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 processed by the contractor, as well as systems that require pre-application before installation, so it is reassuring to have a contractor that supports the preparation of necessary documents and the flow of procedures.
Make sure to complete the procedures specified for each system (for Tokyo’s subsidy, a pre-application is required before installation) 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)
▶ To “Subsidies and Grants that May Be Applicable in Ota City” within this article
Benefits of Introducing Solar Power Equipment
The benefits of introducing solar panels are as follows!
Benefit 1: Economic Advantage
The biggest advantage of introducing solar panels is the economic benefit!
Although the selling price of electricity has decreased compared to 10 years ago, you can benefit by reducing the amount of electricity purchased from the power company by consuming the generated electricity yourself!
As electricity costs rise, the ability to cover your consumption with solar power becomes attractive!
If you wish 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 4 years, and 8.3 yen/kWh from the 5th to the 10th year” for certifications after October 2025, and the same price will apply in the 2026 fiscal year. After the 5th year, it is generally more advantageous to use it at home (self-consumption) rather than selling it, making the combination with a storage battery a viable option.
👉 Ministry of Economy, Trade and Industry | For purchase prices, periods, etc., click here
Benefit 2 Utilization of Subsidies!
The conditions and amounts of subsidies vary by prefecture and municipality, but if you meet the conditions, you may be able to utilize subsidies!
Reducing the actual burden amount through subsidies is a significant advantage!
In the case of Ota City, in addition to national and Tokyo metropolitan programs, there may be eligibility for Ota City’s housing renovation subsidy program (the district’s subsidy program requires construction by small and medium-sized enterprises headquartered within the district).
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 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, this can help reduce the temperature rise of the roof, providing expected heat insulation effects!
(Note that this does not improve the building’s insulation performance itself.)
Advantage 5 Electricity can be used even during power outages!!
If a storage battery is installed, it is possible to use electricity even during emergencies 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 are incurred
A particularly overlooked maintenance cost is for the roof where the solar panels are installed.
If you perform roof renovations 10 to 20 years later, there will be costs for removing and 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 the deterioration of the storage battery.
It would be reassuring to consider maintenance costs in simulations before introducing solar panels!
Point 2 The risk of leaks increases depending on the roofing material
The methods for securing slate roofs and tile roofs vary depending on the construction method, but when using screws or other fasteners to secure the roofing materials and substrate, waterproofing at the fastening points becomes crucial.
In methods that involve making holes in the roof, there is inevitably a risk of leaks.
Of course, we will ensure proper waterproofing, but if you are concerned about making holes, one option is to replace the roofing material with a metal roof and secure the solar panels using the catch method. (The catch method has compatibility conditions between the roofing material and the fasteners, and it cannot be used with all metal roofs.)
Catch-type base fasteners for horizontal metal roofs
Note 3: The roof will become heavier
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.
It is not simply a matter of “this manufacturer has the best solar panels”; it is important to choose solar panels that are suitable for your life plan and building!
Here are some points to consider when comparing solar panels!
Choosing Method 1: Compare based on total output of the roof
When installing solar panels on the roof, it is important to consider how much electricity can be generated in a limited area, and the more electricity generated, the better!
Solar panels come in various sizes and outputs depending on the manufacturer.
For example, a 350W output panel and a 400W output panel may seem like 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,” meaning the number of panels that can be installed may differ even on the same roof due to the size difference.
400W×15 panels = 6kW (total output of the roof)
350W×20 panels = 7kW (total output of the roof)
As shown above, even if the output of a single panel is lower, the total output of the roof may be higher!
It is important to consider the total output of the roof rather than the output of a single panel!
*The above calculations are for total output (kW). The actual electricity generation (kWh) will vary depending on conditions such as roof orientation, slope, and shading.
Choosing Method 2: Compare based on the degradation rate of solar panels
Solar panels have a degradation rate, and their output gradually decreases over 10 years and 20 years.
The degree of output reduction after long-term use varies by product. The manufacturer’s output guarantee values are benchmark figures for warranty purposes and do not indicate the actual degradation rate or power generation amount.
Choosing solar panels by considering not only the initial output but also the degradation rate will lead to a regret-free decision!
How to Choose 3: Compare by Warranty Period
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty periods vary by manufacturer.
Some manufacturers offer a 30-year warranty for output, while others provide a 10-year warranty, so it varies widely!
A longer warranty is always better, so be sure to check the warranty periods and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar and Storage Battery Installation in Ota City
We have compiled frequently asked questions from customers considering the installation of solar panels and storage batteries in Ota City. (Tap to open answers)
How much does it cost to install solar panels and storage batteries in Ota City, 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 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 Ota City?
As of October 6, 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 residential renovation subsidy program in Ota City will end once the budget is exhausted, and the national DR household storage battery program has concluded its public recruitment.
Since the application status may change, please refer to the subsidy and grant section and consult with us before signing a contract.
Can I apply for subsidies after the construction is completed?
For many programs, procedures are required before construction. Tokyo’s subsidies require pre-application before installation, and if you install first, you may be excluded from eligibility. 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. The fixing method varies by construction method, and when fixing brackets to the roofing material or substrate, waterproofing treatment of the fixed parts is crucial.
Kakeru Koumuten Co., Ltd. is a specialist company in exterior renovations with a strong focus on roofing work. Therefore, we will check the condition of the roof before installation and suggest methods such as roof overlay (cover method) or complete replacement if deterioration is advanced.
My roof is old. Should I do a roof renovation first?
It depends on the condition of the roof. If a roof renovation is needed 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 on-site survey!
Is it better to install a storage battery together with solar panels?
If you want to use the generated electricity at night or prepare for power outages, simultaneous installation is recommended. The selling price for electricity will be 8.3 yen/kWh after the fifth year, making it more beneficial to use it in your home rather than selling it.
Additionally, the Tokyo Metropolitan Government’s subsidy for storage batteries is designed for simultaneous installation with solar panels, but you can also apply for the subsidy for storage batteries alone. You can compare the financial simulations for “solar panels only” and “solar panels + storage battery” for your consideration.
How many kW can be installed on my roof? Is it okay for a north-facing roof or one with shadows?
The capacity that can be installed varies depending on the shape, orientation, and size of the roof. At Kakeru Koumuten, we create a layout diagram based on the drawings and on-site survey, and provide you with the installation capacity and power generation simulation.
In Ota City, the environment differs between the northwestern plateau and the southeastern lowland, and the shadows cast by neighboring houses, buildings, and trees vary from one house to another. You can check the expected power generation through the power generation simulation.
How long will the construction period be?
In the above construction example (solar panel 4.3 kW + storage battery), it took about 3 days. The duration may vary if roofing work is done simultaneously or depending on the shape of the roof and installation capacity.
Please note that there will be additional time 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), from the certification 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 price applied for the 2026 fiscal year.
The idea is to recover the initial costs more quickly in the first 4 years and then focus on self-consumption. Kakeru Koumuten provides financial simulations that take into account loan interest rates and electricity costs.
Can you handle maintenance and inspections after installation?
Yes, we can. Kakeru Koumuten sends out annual after-service maintenance DM notices and visits customers who wish for inspections. We can also clean solar panels using a special brush if the power generation decreases due to dirt.
It can be difficult to check areas on the roof 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?
It is possible. Kakeru Koumuten Co., Ltd. can detach and reattach solar panels in-house, allowing us to perform roof overlay (cover method) or re-roofing after removing the panels, and we will handle everything consistently until they are reinstalled. 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 Ota City, please consult Kakeru Koumuten
Our company handles many exterior renovations, including solar panels, roof work, and exterior wall work in Ota City, Tokyo.
We have received requests from many customers, including renovation companies and real estate agencies!
Kakeru Koumuten promises “high-quality renovations at low cost”, and we have received positive feedback from numerous customers.
We continue to update our construction performance 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 (cover method) and re-roofing but also partial roof repairs, exterior painting, and exterior wall cover methods.
We are happy to assist with small jobs such as partial repairs and rain gutter cleaning!
In urgent cases such as water leakage work, 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 focused on profit!
We always stand in our customers’ shoes and propose the best construction plans!
We are confident that we will not be outdone in terms of cost, quality, and organization compared to other companies in exterior construction!
We are confident, so we welcome competitive quotes!
Estimates are completely free, and if we are found to be inferior to other companies, you are free to decline!
Characteristics of Ota City, Tokyo and Points for Solar Construction
Ota City, Tokyo, is the largest ward in terms of area among the 23 wards, facing Tokyo Bay to the east and the Tama River to the west and south. According to the official page of Ota City, it has an area of 61.86 km2 (approximately 15.7 km east-west and 9.4 km north-south), and is divided into two topographies: the hilly area at the southeastern edge of the Musashino Plateau in the northwest and the lowland consisting of alluvial plains and reclaimed land in the southeast.
We have summarized the topography and residential environment of Ota City and the points to consider when installing solar panels and storage batteries below. (Tap to open)
View the characteristics of Ota City, Tokyo and points for solar construction
■ The environment of houses differs between plateaus and lowlands. Check the roof orientation and shadows
The highest point in Ota Ward is about 42.5m near Denenchofu, decreasing towards the southeast, with the high points in the lowland area being about 5m and around 1m at the coastline. The plateau area has been developed into residential areas after the Great Kanto Earthquake, while the lowland area has developed as commercial and industrial regions.
In densely populated areas, the shadows cast by neighboring houses and buildings vary from house to house. Since solar panels generate less electricity when shaded, Kakeru Koumuten creates layout diagrams based on blueprints and the actual site conditions, and confirms them through power generation simulations.
■ The annual sunshine hours in Tokyo are about 1,927 hours
According to the Japan Meteorological Agency’s average values (1991–2020), the annual sunshine hours in Tokyo are about 1,927 hours.
Power generation varies by season, so conducting annual power generation simulations and selecting battery capacity to match the times of high electricity usage are key points.
■ Consider salt air and humidity in areas close to Tokyo Bay and the Tamagawa River
Ota Ward faces Tokyo Bay to the east and the Tamagawa River to the west and south. In areas close to the sea or river, the salt contained in the sea breeze may affect the fixtures and equipment around the roof. It is important to choose equipment such as panels, mounting frames, and power conditioners that are suitable for your location, based on the installation conditions specified by the manufacturer (distance from the coast and salt damage specifications, etc.).
■ In lowlands and reclaimed land, also check the installation location of equipment
The southeastern lowland area of Ota Ward consists of alluvial plains formed by the sediment of the Tamagawa River and the coastline, along with the subsequent reclaimed land. Since the expected flooding varies depending on your location, it is reassuring to check the flood risk map for your location when deciding on the installation location for batteries and power conditioners.
■ In areas close to residences, shops, and factories, planning for delivery and scaffolding is also important
The lowland area is part of the Keihin Industrial Zone, where residences are located near shops and factories. In houses with narrow sites or front roads, careful planning for scaffolding and equipment delivery is necessary. Kakeru Koumuten will respond according to the site 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 many years, it is important to check the condition of the roofing materials and substrate before installing solar panels. Depending on the condition of the roof, installing them simultaneously with roof renovations can help reduce future costs for removing and reinstalling solar panels.
■ Subsidies require separate applications for Tokyo and Ota Ward
Subsidies for solar power and storage batteries in Tokyo require prior application from the Cool Net Tokyo official page. Ota Ward’s housing renovation subsidy program requires construction by small and medium-sized businesses headquartered within the ward. It is important to check the procedures and conditions for each program in advance, along with the timing of the construction.
Our company serves Kanagawa Prefecture and Tokyo, and we handle many exterior and solar power projects in Ota Ward, Tokyo.
We are happy to assist with partial roof repairs such as roof overlay work, roof replacement, and leak repairs, as well as other repairs! Please feel free to consult us about any sudden troubles!
Service Area in Ota Ward, Tokyo
Kakeru Koumuten accepts requests throughout Kanagawa Prefecture and all of Tokyo.
List of Areas in Ota Ward, Tokyo
Ikegami, Ota Ward / Ishikawacho, Ota Ward / Unoki, Ota Ward / Omori Kita, Ota Ward / Omori Naka, Ota Ward / Omori Nishi, Ota Ward / Omori Higashi, Ota Ward / Omori Honcho, Ota Ward / Omori Minami, Ota Ward / Kamata, Ota Ward / Kamata Honcho, Ota Ward / Kami Ikedai, Ota Ward / Kita Kojiya, Ota Ward / Kita Chitose, Ota Ward / Kita Magome, Ota Ward / Kita Reimachi, Ota Ward / Kuga Hara, Ota Ward / Keihinjima, Ota Ward / Sanno, Ota Ward / Shimo Maruko, Ota Ward / Jonanjima, Ota Ward / Showajima, Ota Ward / Shin Kamata, Ota Ward / Tamagawa, Ota Ward / Chidori, Ota Ward / Chuo, Ota Ward / Denenchofu, Ota Ward / Denenchofu Honcho, Ota Ward / Denenchofu Minami, Ota Ward / Tokai, Ota Ward / Naka Ikegami, Ota Ward / Naka Magome, Ota Ward / Naka Rokugo, Ota Ward / Nishi Kamata, Ota Ward / Nishi Kojiya, Ota Ward / Nishi Magome, Ota Ward / Nishi Reimachi, Ota Ward / Nishi Rokugo, Ota Ward / Haginaka, Ota Ward / Haneda, Ota Ward / Haneda Asahi-cho, Ota Ward / Haneda Airport, Ota Ward / Higashi Kamata, Ota Ward / Higashi Kojiya, Ota Ward / Higashi Magome, Ota Ward / Higashi Reimachi, Ota Ward / Higashi Yaguchi, Ota Ward / Higashi Yukigaya, Ota Ward / Higashi Rokugo, Ota Ward / Furusato no Hamabe Park, Ota Ward / Heiwajima, Ota Ward / Heiwa no Mori Park, Ota Ward / Hon Haneda, Ota Ward / Minami Kamata, Ota Ward / Minami Kuga Hara, Ota Ward / Minami Chitose, Ota Ward / Minami Magome, Ota Ward / Minami Yukigaya, Ota Ward / Minami Rokugo, Ota Ward / Yaguchi, Ota Ward / Yukigaya Otsuka-cho, Ota Ward
・Trust Kakeru Koumuten for exterior wall painting in Ota City, Tokyo!
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・Trust Kakeru Koumuten for exterior renovations in Ota City, 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 comparative estimates and key points!
・12 major manufacturers of solar power generation! Features and selection tips included!
・What are the installation costs for solar power generation? Comprehensive tips for reducing costs!
・What are the best locations for installing solar power generation? Key points for site selection included!
・Check out our solar power generation estimates here!
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contact Kakeru Koumuten Co., Ltd.
Kakeru Koumuten is a young company whose team is, on average, in their late twenties, but our skills are second to none.
Our greatest strength is that we handle scaffolding, roofing and painting entirely in-house. In an industry where these tasks are usually divided among contractors, our complete service simplifies project management and helps keep costs down. Above all, if a problem arises, we respond promptly.
We proudly describe ourselves as the youngest and most helpful renovation company in Kanagawa!
