Leave Your Solar Panel Installation Work in Ota City, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and 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 withsolar panel and battery installation considering roofs and waterproofing!
“How to Choose a Solar Panel Contractor in Ota City”
“Costs for Solar Panel and Battery Installation”
“Subsidies Available for Solar System Installation in Ota 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 you do not regret your solar panel installation, we recommend obtainingestimates 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
- Possible 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 Installation Company in Ota City, Tokyo
- Benefits of Introducing Solar Equipment
- Points to Note When Introducing Solar Power Generation
- How to Choose Solar Panels
- Frequently Asked Questions About Solar and Storage Battery Installation in Ota City
- If You Are Looking for a Solar Panel Installation Company in Ota City, Contact Kakeru Koumuten
- Characteristics of Ota City, Tokyo and Points for Solar Construction
- Service Area in Ota City, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Ota City, Tokyo
Regarding why we are entrusted with solar panel installation by customers in Ota City, Tokyo,
One reason is that “Kakeru Koumuten covers Kanagawa and Tokyo as service 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 Can Also Handle Exterior Renovations Other Than 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 expertise in roofing to avoid maintenance issues 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 prepared the following warehouses and material storage areas to provide low-cost, high-quality solar and exterior renovation work.
We have established five bases centered around Yokohama City, Kanagawa Prefecture for material storage and showrooms.
In-house Scaffolding Materials
To ensure safety during work on the roof, we have our own scaffolding materials necessary for temporary scaffolding depending on the construction conditions, and we can assemble the scaffolding ourselves.
By not outsourcing scaffolding work and using our own scaffolding team, we can also cut costs for scaffolding work.
We own scaffolding materials for approximately 50 detached houses!
In Ota Ward, where the terrain varies from residential areas on plateaus to lowlands along the Tamagawa River and coastal areas, our in-house scaffolding team will plan the scaffolding according to the local conditions.
Storage of Materials in Our Large Warehouse
We store roofing materials and paints, and we can also store removed solar panels.
By ordering a large quantity of materials at once, you canpurchase materials at a lower cost!
Additionally, we always have roofing materials in stock, so we canrespond quickly 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 waste disposal costs.
Exterior remodeling dedicated showroom
In the showroom, not only can you have meetings, but you can also
check the actual foundation brackets for solar panels and see how they are installed on roofing materials!
It is also possible to simulate the revenue and installation costs when introducing solar panels!
Since roofing and exterior wall work are often involved, 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 its complete in-house construction.
By having Kakeru Koumuten handle everything from inquiries to project completion in a consistent manner, we can keep costs down and provide high-quality roof renovations.
Additionally, one representative will assist you from the estimate to the completion of the work.
Since the same person will handle sales and construction management, smooth communication is possible.
We can provide consistent in-house construction from temporary scaffolding installation to exterior wall painting and roof renovations!
4. Various Permits and Skilled Workers
We have obtained construction industry licenses and permits for industrial waste collection and transportation!
We also have nationally certified sheet metal and painting technicians, and we are confident in our construction skills.
We can also handle large-scale roofing projects such as factories!
5. Warranty and Aftercare
In addition to the manufacturer’s warranty for solar panel installation, we also provide our own construction warranty (leakage warranty)!
(The construction warranty for solar panel installation is 10 years. Depending on the condition of the roof before installation, we may not be able to provide a warranty unless roof renovations are performed. The construction warranty is separate from the manufacturer’s product warranty, and the scope and conditions vary depending on the warranty details.)
Aftercare is available every year, and we send out notification DM each year.
If you have questions about the warranty, please click on the image above!
6. Flexible and Prompt Response
Our company is equipped to handle various roofing troubles and situations.
Even if you cannot access the roof at high altitudes, we can utilize drones to assist!
During leak investigations, we can also conduct surveys using a thermal imaging camera.
If the power generation of solar panels decreases due to dirt or other factors, we can also provide cleaning services using specialized brushes.
We will respond according to your preferences.
7. Human Resource Development
To improve skills, we create various roofing models and conduct practical training.
Since the construction methods vary depending on the shape and slope of the roof, we regularly provide technical training to ensure that each staff member can handle various cases.
8. Creation of Easy-to-Understand Materials and Simulations
At Kakeru Koumuten, we provide not only “estimates,” “layout diagrams,” and “power generation simulations” but also a “solar construction 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 construction will receive materials that clearly summarize important points and disadvantages!
We encourage you to obtain comparative estimates and compare them with other companies’ plans!
Roof Inspection Before Installing Solar Panels
Once solar panels are installed, they will remain on the roof for 20 to 30 years.
Confirming “Is it okay to install them directly on the current roof?” before installation is the key point to prevent leaks and unnecessary expenses!
Kakeru Koumuten, which specializes in roofing work, has summarized the items to check before installation.
| 1. Types of Roofing Materials and Age | The fixing method varies depending on the roofing material, such as slate, tile, metal roofs, and flat roofs (rooftop waterproofing). If the remaining lifespan of the roofing material is short, we may suggest roof renovation first. |
| 2. Condition of Substrate and Waterproof Sheet | If the sheathing or roofing (waterproof sheet) under the roofing material is damaged, it will affect the fastening strength and waterproofing. We will also check for any signs of leaks. |
| 3. Orientation, Slope, and Shadows of the Roof | The orientation and slope of the roof surface, as well as shadows from neighboring houses, trees, and utility poles, will affect the amount of electricity generated. We will create a layout diagram from the drawings and the site, and you can confirm it with a power generation simulation. |
| 4. Shape of the Roof and Usable Area | The number of panels that can be installed (installation capacity) is determined by the shape and size of the roof. Since the number of panels that can be installed varies depending on the size of the panels, we will compare based on the overall output of the roof. |
| 5. Fixing Method and Waterproofing Details | We will check whether the method involves drilling holes in the roofing material for fastening or using brackets to secure the roofing material. The fixing method varies by technique, so please confirm the waterproofing treatment method for the fixing parts during the estimate. |
| 6. Weight of the Roof | The roof will become heavier due to the panels. After investigating the existing roof, substrate, and load-bearing capacity, switching to lighter roofing materials may also be an option if necessary. |
| 7. Installation Location of Equipment and Wiring | We will confirm the installation location of the power conditioner and storage battery, as well as the wiring route to the distribution board. The length of the wiring will also affect the cost. |
Fixing Methods and Checkpoints by Roofing Material
| Roof Material | Main Fixing Method | Pre-Installation Check Points |
|---|---|---|
| Slate Roof | Varies by method (e.g., fixing brackets to the roof material and substrate with screws) | Waterproof treatment of fixing parts, cracks or deterioration of slate, condition of 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 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 framework | Type and deterioration status of the waterproof layer, waterproofing around the framework. Consider in conjunction with the timing of waterproofing work. |
If you perform roof renovations 10 to 20 years after installation, there will be additional costs for the removal and reinstallation of solar panels. If the roof is deteriorating, it may be more cost-effective in the long run to renovate to a highly durable roofing material before installation.
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 Ota City, Tokyo
Subsidies and Grants That May Be Applicable inOta City, Tokyo
If you are introducing solar panels or storage batteries in Ota City, Tokyo, there may be systems from the “National Government,” “Tokyo Metropolitan Government,” and “Ota City” that are applicable.
The following information is based on the official pages of each system as of October 6, 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 “Reiwa 8 Year Household Solar Power Generation Promotion Project” (Cool Net Tokyo) | New installation of certified solar cell modules on residential properties within Tokyo, with systems under 50kW. Pre-application before installation is required. | Existing homes: 150,000 JPY/kW for 3.75kW or less (maximum 450,000 JPY), 120,000 JPY/kW for over 3.75kW New homes: 120,000 JPY/kW for 3.6kW or less (maximum 360,000 JPY), 100,000 JPY/kW for over 3.6kW (Additional costs for mounting frames, waterproofing work, and renovation defect insurance, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 to March 30, 2029 |
| Tokyo Metropolitan Government “Reiwa 8 Year Household Storage Battery Promotion Project” (Cool Net Tokyo) | New installation of storage batteries in residential properties within Tokyo, with SII registered equipment. This project is intended for simultaneous installation with solar power, but applications can be made for storage batteries alone. Pre-applications after October 1, 2026 will only be eligible for SII registered products for Reiwa 8. | Storage battery package: 100,000 JPY/kWh (maximum 1,200,000 JPY per household) Storage battery unit expansion: 60,000 JPY/kWh (maximum 720,000 JPY per household) (Additional incentives for participation in DR demonstrations, etc.) |
Pre-application: From May 29, 2026 Grant application and performance report: From June 30, 2026 |
| Ota City “Housing Renovation Subsidy Project” Reiwa 8 Year | Residents of Ota City with a resident registration from January 1, 2026, to the application date. Installation of solar power generation and storage batteries is included in A construction. Construction must be performed by small and medium-sized enterprises headquartered in the city. | 10% of the eligible amount (maximum 200,000 JPY) If used in conjunction with other programs, 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 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 30% and 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 works 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 | Once the budget limit is reached, the program will end. Please check the official website for the current status of applications. |
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. For the subsidy program in Ota City, the condition is that the construction must be carried out by a small or medium-sized business with its headquarters located within 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 vary by program, so please confirm before signing a contract or starting construction.
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 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 yen/kW for systems up to 3.75kW (maximum 450,000 yen), and 120,000 yen/kW for systems exceeding 3.75kW. Additionally, there are extra items for 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 60,000 yen per kWh for the addition of storage battery units (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 products will be eligible. This program is intended for simultaneous installation with solar power, but applications can 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 decarbonization). 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 close 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%. Please note that our company, Kakeru Koumuten Co., Ltd., is headquartered in Aoba Ward, Yokohama City, and therefore does not qualify as a contractor for this subsidy project.
👉 Click here for the official page of Ota City
National Subsidy “DR Home Battery Project (Support Project for Home Battery System Installation for DR Resource Introduction)”
The national government has been implementing the “DR Home Battery Project” to support the installation of home batteries.
This project targets individuals who are newly introducing registered battery 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 subsidy amount 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 public recruitment for the previous fiscal year’s supplementary budget also ended on July 2, 2025). Applications are currently not possible, so please check the official website 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 site of the DR Home Battery Project
Solar Panel Installation & Battery Installation Price List
⇧Service Menu | For Costs of Solar Panel Removal and Water Heater Dismantling, Click Here
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and storage batteries should be checked separately as “Equipment Costs (Device Costs)” and “Construction Costs.”
Even for the same “Complete Solar Panel Installation,” the amount can vary significantly depending on the installation capacity, equipment grade, and roof condition.
Considerations for Installation Capacity (kW) and Storage Battery Capacity (kWh)
The installation capacity of solar panels is determined by “Output of One Panel (W) × Number of Panels”, with the unit being kW (kilowatts). Storage batteries are compared based on the amount of electricity they can store, measured 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 based on 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 | For Costs of Solar Panel Installation and Storage Battery Installation, Click Here
Items to Check in the Estimate (Cost Verification)
When comparing estimates, it is common to compare different capacities and equipment by only looking at the amounts. Please check if the following items are clearly stated in each company’s estimate!
| 1. Solar Panels | Manufacturer, model number, output per panel (W), number of panels, total installation capacity (kW) are listed. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, installation location (indoor/outdoor). Also check if it is a type that controls the battery as a unit. |
| 3. Storage Battery | Manufacturer, model number, capacity (kWh), range available during power outages (entire house or specific circuits), installation location. |
| 4. Mounting Frame & Fittings | Name of fittings suitable for roofing materials and method of securing them (whether it is a method that drills holes or a method that grips and secures). |
| 5. Wiring & Electrical Work | Wiring route and length, work around the distribution board, presence of a monitor to check power generation. |
| 6. Roof Reinforcement & Waterproofing | Details of waterproofing treatment at fixed points, whether necessary roof repairs and substrate reinforcements are included. |
| 7. Applications | How much support is included for applications to the power company, certification applications for selling electricity (FIT), and subsidy applications. |
| 8. Scaffolding | Scope and quantity of scaffolding. If roof work and exterior painting are done simultaneously, check that the same scope and quantity are not double-counted. |
| 9. Removal & Disposal | Whether the removal of existing solar water heaters or old panels and disposal costs for waste materials are included. |
| 10. Tax Classification & Warranty | Whether prices are tax-inclusive or tax-exclusive, conditions under which additional costs may arise, and details and duration of manufacturer and workmanship warranties. |
If the capacities differ, both the price and power generation will change. Kakeru Koumuten Co., Ltd. warmly welcomes comparative estimates, so if you bring estimates from other companies, we will explain the differences item by item!
Self-Estimate and Profit Simulation for Solar Power Generation
With the simulator above,
you can obtain 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 Feedback
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customer reviews
Asao-ku, Kawasaki City | We received reviews about the ridge cap and rain gutter replacement work!
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customer reviews
Kohoku-ku, Yokohama | We received reviews about the roof overlay (cover method)!
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customer reviews
Kohoku-ku, Yokohama | We Received Reviews About Exterior Painting!
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customer reviews
Hodogaya-ku, Yokohama | We received reviews about our exterior fence construction!
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customer reviews
Tsurumi-ku, Yokohama | We received reviews about roof and exterior wall painting, as well as metalwork and rain gutter replacement work!
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customer reviews
Higashiyamato City, Tokyo | We received reviews about exterior painting and roof overlay (cover method)!
Case Studies of Solar Panel Installations
| 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 Manufacturing/Aluminum Catch Type Hardware |
| Fixing Method & Waterproofing Details |
| 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 |
| About 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 the grant, 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.
Therefore, when requesting solar panel installation and battery installation work, let’s check the following 4 points.
● Have extensive knowledge not only about solar panels but also about roofs
● Confirm the existence of warranties and aftercare maintenance
● Obtain estimates from multiple contractors (3 companies as a guideline)
● Check if they provide support for subsidy applications
By confirming the above 4 points, you will be able to choose a reliable contractor.
Knowledge about roofs as well as solar panels
Improper installation of solar panels can sometimes be caused by a lack of knowledge and verification regarding roofs and waterproofing.
While knowledge about solar panels is certainly important, understanding the roof and waterproofing at the installation site of the solar panels is also crucial.
⚠︎Examples of troubles due to 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, necessitating a renovation for removal and reinstallation of the solar panels within a few years
・Misjudging the type of waterproofing and performing 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 unforeseen troubles.
▶ Go to “Roof Verification Before Installing Solar Panels” in this article
Confirm the existence of warranties and aftercare maintenance
When choosing a solar installation contractor, confirm the existence of warranties. It is important to check not only the duration of the warranty but also the coverage, exclusions, and cost conditions.
While solar panels and battery units come with manufacturer warranties, it is also important to check for the existence of a workmanship warranty in case leaks occur after installation!
For contractors that provide a workmanship warranty, if leaks occur after installation, they may be able to respond under the warranty, provided it is within the warranty period and conditions.
Additionally, some contractors offer after-sales service separate from warranties, so be sure to check if the contractor you are considering has after-sales service.
Changes or damage on the roof may occur in areas that are not visible, so there is a possibility that customers may not notice them themselves.
By conducting inspections during after-sales maintenance, we can easily prevent major repairs or failures by discovering abnormalities early!
Kakeru Koumuten Co., Ltd. provides a leak warranty as part of the workmanship warranty for solar panel installations. (The warranty for solar panel installations is 10 years, and depending on the condition of the roof before installation, we may not be able to provide a warranty unless roof renovations are performed.)
We also conduct after-sales maintenance and 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, 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 careful comparisons to make your judgment! If the rank of auxiliary materials is low or if processes are skipped, costs can be reduced, so avoid judging solely based on price!
▶ Go to “Breakdown of Installation Capacity, Equipment, and Construction Costs” in this article
Check if they provide support for subsidy applications
There may be subsidies available for solar panel installations and battery installations, but if the order of procedures is incorrect or if there are deficiencies in the documents, the subsidy may not be granted.
There are systems that require personal applications and cannot be submitted 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.
Complete the procedures specified for each system (for Tokyo subsidies, 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 may vary depending on the system)
▶ Go 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 Benefits
The biggest benefit of introducing solar panels is the economic advantage!
Although the selling price of electricity has decreased compared to ten years ago, you can gain benefits by reducing the electricity you purchase from power companies through self-consumption of generated electricity!
As electricity prices rise, the ability to cover your consumption with solar power becomes attractive!
If you plan to use the generated electricity at night, installing a storage battery is essential!
Furthermore, the selling price (FIT) for residential use (under 10kW) will be set at “24 yen/kWh for the first four years, and 8.3 yen/kWh from the fifth to the tenth year” for certifications after October 2025, and the same price will apply for the 2026 fiscal year. After the fifth year, it is generally more advantageous to use it in your home (self-consume), 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 requirements, 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 systems, there is a possibility of being eligible for Ota City’s housing renovation subsidy program (the condition for the city’s subsidy program is that the work must be performed by a small business operator with a headquarters in the city).
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 may have operational noise.)
Benefit 4 Expect heat insulation effects!!
By installing the panels on the roof or rooftop, they block direct sunlight to the roof.
Especially in summer, it can help reduce the temperature rise of the roof, so heat insulation effects can be expected!
(Note that this does not improve the building’s insulation performance itself.)
Benefit 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 maintenance cost that is particularly easy to overlook is the roof where the solar panels are installed.
If you perform roof remodeling 10 to 20 years later, there will be costs for removing and reinstalling the solar panels.
If the existing roof is deteriorated, it is reassuring to remodel 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 deterioration of the storage battery.
It would be reassuring to request a simulation that also 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 using screws or other fasteners to secure the roofing material and substrate, waterproofing treatment at the fastening points becomes crucial.
In methods that involve making holes in the roof, the risk of leaks inevitably arises.
Of course, we will ensure 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
As solar panels are added, the roof will become heavier. After investigating the existing roof, substrate, and load-bearing capacity, replacing 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 the limited area, and the more electricity generated, the better!
Solar panels vary in size and output depending on the manufacturer.
For example, a 350W output panel and a 400W output panel may seem that the higher output panel is better at first glance.
However, if the panel size does not fit well with the roof, “20 panels of 350W can be installed, while only 15 panels of 400W can be installed,” leading to different installation capacities on the same roof due to the size difference.
400W×15 panels = 6kW (total output of the roof)
350W×20 panels = 7kW (total output of the roof)
As shown above, even if the output of a single panel is lower, the total output of the roof may be higher!
It is important to consider the total output of the roof rather than the output of a single panel!
*The above calculations are for total output (kW). The actual power generation (kWh) will vary depending on conditions such as 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 value is a benchmark for the warranty and does not indicate the actual degradation rate or the amount of electricity generated.
Choosing solar panels while considering both the initial output and the degradation rate will lead to a decision without regrets!
How to Choose 3: Compare by Warranty Period
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty periods differ by manufacturer.
For 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 period 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 the 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 available on the solar panel installation and storage battery installation pricing page. We will create a layout diagram from the drawings and on-site survey and provide a free estimate!
Are there any subsidies available for solar and storage battery installation in 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 project in Ota City will end once the budget is exhausted, and the national DR household storage battery project has already closed 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 even 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. The procedures differ by program.
Since the order of procedures varies by program, please confirm before signing a contract and starting construction.
Can solar panels be installed on a slate roof? I’m worried about leaks.
It is possible to install on a slate roof, but it is necessary to check the condition of the roofing material and substrate. The fixing method varies by construction method, and in methods that fix brackets to the roofing material or substrate, waterproofing treatment of the fixed parts is essential.
Kakeru Koumuten Co., Ltd. is a specialized exterior renovation company strong in roofing work, so we will check the condition of the roof before installation. If deterioration is progressing, we can also suggest methods such as roof overlay (cover method) or complete replacement before installation.
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 about the installation process after checking the roof’s condition through a site survey!
Is it better to install a storage battery together with solar panels?
For those who want to use generated electricity at night or prepare for power outages, simultaneous installation is recommended. The selling price for electricity will be 8.3 yen/kWh after the fifth year, making it more advantageous to use it in your home rather than selling it.
Additionally, the Tokyo Metropolitan Government’s subsidy for storage batteries is designed for simultaneous installation with solar panels, but you can also apply for the subsidy for storage batteries alone. You can compare “solar panels only” and “solar panels + storage battery” through a financial simulation.
How many kW can be installed on my roof? Is it okay for north-facing or shaded roofs?
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 from the drawings and site survey, and we will provide you with the installation capacity and power generation simulation.
In Ota City, the environment differs between the northwestern plateau and the southeastern lowlands, and the shading from neighboring houses, buildings, and trees varies 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 (4.3 kW solar panel + 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 an additional 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 (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, and the same price will apply for the 2026 fiscal year.
The idea is to recover the initial costs quickly in the first 4 years and then focus on self-consumption. Kakeru Koumuten provides a financial simulation considering 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 notices via direct mail, and we visit customers who wish to have inspections. We can also clean solar panels with a special brush if the power generation decreases due to dirt.
It is difficult to check areas on the roof by yourself, so please feel free to consult us if you have any concerns.
Can you also renovate a roof that already has 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 reinstallation. 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 Ota City, please consult Kakeru Koumuten
Our company handles many exterior renovations, including solar panel installations, 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 costs”, and we have received great feedback from numerous customers.
We continue to update our construction achievements every year and will strive to improve quality to satisfy even more customers in the future.
Our company can perform not only roof overlay (cover method) 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 handle small jobs such as partial repairs and rain gutter cleaning!
In urgent cases such as leak repairs, we may be able to provide emergency measures without setting up scaffolding, as long as safety can be ensured, so please consult with us!
“I want to know about recommended solar panels“, “I want to keep costs down as much as possible“, “I just want an estimate for now“, we will provide optimal solutions for specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s position and will propose the best construction plan!
We are confident that we will not be outdone by other companies in terms of cost, quality, and organization for exterior work!
We are confident, so we welcome competitive estimates!
Estimates are completely free, and if our company is found to be inferior to others, you are free to decline!
Characteristics of Ota City, Tokyo and Points for Solar Work
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 terrains: the hilly area at the southeastern edge of the Musashino Plateau in the northwest and the lowland areas 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 work
■ The environment of houses differs between plateaus and lowlands. Check the roof orientation and shadows.
The highest point in Ota City is about 42.5m near Denenchofu, decreasing towards the southeast, with the high point in the lowland area being about 5m and approximately 1m at the coastline. The plateau area has developed into residential areas after the Great Kanto Earthquake, while the lowland area has developed as commercial and industrial zones.
In densely populated areas, the shadows cast by neighboring houses and buildings vary from one house to another. Since solar panels generate less electricity when shaded, Kakeru Koumuten Co., Ltd. creates layout diagrams based on blueprints and the actual site conditions, and we confirm this through power generation simulations.
■ Tokyo’s annual sunshine hours are about 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), Tokyo’s annual sunshine hours are about 1,927 hours.
Power generation varies by season, so conducting annual power generation simulations and selecting battery capacity according to peak electricity usage times are key points.
■ Consider salt air and humidity near Tokyo Bay and the Tamagawa River
Ota City faces Tokyo Bay to the east and the Tamagawa River to the west and south. In areas close to the sea or rivers, the salt contained in sea breezes may affect the fittings and equipment around the roof. It is important to choose equipment such as panels, frames, fittings, and power conditioners that match your location after confirming the installation conditions set by the manufacturers (distance from the coast, salt-resistant specifications, etc.).
■ In lowlands and reclaimed land, also check the installation location of equipment
The lowland area in the southeastern part of Ota City consists of alluvial plains formed by the Tamagawa River and coastal deposits, along with the subsequent reclaimed land. Since the risk of flooding varies depending on your location, it is reassuring to check the flood risk for your location on a hazard map 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, shops, and factories are located nearby. For houses with narrow lots or front roads, careful planning for scaffolding and equipment delivery is necessary. Kakeru Koumuten Co., Ltd. will respond to site conditions with our own scaffolding team and owned scaffolding materials.
■ Check the roof condition according to the age of the building
For houses that have been built for several years, it is important to check the condition of the roofing materials and substrate before installing solar panels. Depending on the roof’s condition, installing them simultaneously with roof renovations can help reduce future costs for removing and reinstalling solar panels.
■ Subsidies require separate applications for Tokyo and Ota City
Subsidies for solar power and storage batteries in Tokyo require pre-application from the official Cool Net Tokyo page. Ota City’s housing renovation subsidy program requires construction by small and medium-sized enterprises headquartered within the city. 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 construction projects in Ota 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 about any sudden troubles!
Service Area in Ota City, Tokyo
Kakeru Koumuten Co., Ltd. accepts requests throughout Kanagawa Prefecture and Tokyo.
List of Areas in Ota City, Tokyo
Ikegami, Ota City / Ishikawacho, Ota City / Unoki, Ota City / Omori Kita, Ota City / Omori Naka, Ota City / Omori Nishi, Ota City / Omori Higashi, Ota City / Omori Honcho, Ota City / Omori Minami, Ota City / Kamata, Ota City / Kamata Honcho, Ota City / Kami Ikedai, Ota City / Kita Kojiya, Ota City / Kita Chitose, Ota City / Kita Magome, Ota City / Kita Reimachi, Ota City / Kuga Hara, Ota City / Keihinjima, Ota City / Sanno, Ota City / Shimo Maruko, Ota City / Jonanjima, Ota City / Showajima, Ota City / Shin Kamata, Ota City / Tamagawa, Ota City / Chidori, Ota City / Chuo, Ota City / Denenchofu, Ota City / Denenchofu Honcho, Ota City / Denenchofu Minami, Ota City / Tokai, Ota City / Naka Ikegami, Ota City / Naka Magome, Ota City / Naka Rokugo, Ota City / Nishi Kamata, Ota City / Nishi Kojiya, Ota City / Nishi Magome, Ota City / Nishi Reimachi, Ota City / Nishi Rokugo, Ota City / Haginaka, Ota City / Haneda, Ota City / Haneda Asahi-cho, Ota City / Haneda Airport, Ota City / Higashi Kamata, Ota City / Higashi Kojiya, Ota City / Higashi Magome, Ota City / Higashi Reimachi, Ota City / Higashi Yaguchi, Ota City / Higashi Yukigaya, Ota City / Higashi Rokugo, Ota City / Furusato no Hamabe Park, Ota City / Heiwajima, Ota City / Heiwa no Mori Park, Ota City / Hon Haneda, Ota City / Minami Kamata, Ota City / Minami Kuga Hara, Ota City / Minami Chitose, Ota City / Minami Magome, Ota City / Minami Yukigaya, Ota City / Minami Rokugo, Ota City / Yaguchi, Ota City / Yukigaya Otsuka-cho, Ota City
・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. construction achievements
・Kakeru Koumuten Co., Ltd. aftercare services
・Kakeru Koumuten Co., Ltd. construction menu and price list
・Kakeru Koumuten Co., Ltd. staff blog and announcements
・Explaining the importance of comparative estimates and key points!
・Top 12 solar power generation manufacturers! Features and selection tips included!
・What are the installation costs for solar power generation? Comprehensive tips to reduce costs!
・What are the best locations for solar power installation? Key points for site selection included!
・Find out about solar power generation estimates here!
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contact Kakeru Koumuten Co., Ltd.
Kakeru Koumuten is a young company whose team is, on average, in their late twenties, but our skills are second to none.
Our greatest strength is that we handle scaffolding, roofing and painting entirely in-house. In an industry where these tasks are usually divided among contractors, our complete service simplifies project management and helps keep costs down. Above all, if a problem arises, we respond promptly.
We proudly describe ourselves as the youngest and most helpful renovation company in Kanagawa!
