Leave Your Solar Panel Installation in Arakawa, Tokyo to Kakeru Koumuten Co., Ltd.!
For solar panel and battery installation in
Arakawa, Tokyo,
trust Kakeru Koumuten!
Kakeru Koumuten is a company specializing in exterior renovations.
As a company strong in roofing work, we are entrusted withsolar panel and battery installation considering roofing and waterproofing!
“How to Choose a Solar Panel Contractor in Arakawa, Tokyo”
“Costs for Solar Panel and Battery Installation”
“Subsidies Available for Solar System Installation in Arakawa, Tokyo”
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 have no regrets about 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 Arakawa, Tokyo
- Roof Inspection Before Installing Solar Panels
- Possible Subsidies and Grants Available in Arakawa, Tokyo
- Pricing Table 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 Arakawa, 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 Arakawa, Tokyo
- If You Are Looking for a Solar Panel Installation Company in Arakawa, Tokyo, Contact Kakeru Koumuten
- Characteristics of Arakawa, Tokyo and Points for Solar Construction
- Service Area in Arakawa, Tokyo
Reasons Why Kakeru Koumuten is Chosen for Solar Panel Installation in Arakawa, Tokyo
Regarding why our company is entrusted with solar panel installation by customers in Arakawa, Tokyo,
“Our Unique Strengths in Solar Panel Installation That Cannot Be Imitated by Other Companies”
have 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!
Problems 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 one is knowledgeable about solar panels, there may be cases where the roof and waterproofing at the installation site are outside their 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 solar work and exterior renovations at low cost and high quality.
We have established five bases for material storage and showrooms.
In-house Ownership of Scaffolding Materials
To ensure safety during work on the roof, we own the scaffolding materials necessary for temporary scaffolding according to the construction conditions and can assemble the scaffolding in-house.
By not outsourcing scaffolding work and conducting it with our own scaffolding team, we can also cut costs for scaffolding work.
We own scaffolding materials for approximately 50 detached houses!
Even in cases where there are elevation differences on the site, 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 a stock of roofing materials, allowing us torespond 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!
We can also provide simulations of the revenue and installation costs when introducing solar panels!
Since roofing and exterior wall work often accompany each other, we also have samples of roofing materials and models that explain 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 a consistent system from inquiry to project completion, Kakeru Koumuten can provide high-quality roof renovations at reduced costs.
Additionally, one representative will handle everything from the estimate to the completion of the work.
Since the representative does not change, whether it be the sales or construction management staff, smooth communication is possible.
We can provide consistent in-house construction from temporary scaffolding installation, exterior wall painting, to roof renovations!
4. Various Permits and Skilled Workers
We have obtained permits for the construction industry and for the collection and transportation of industrial waste!
We also have nationally certified sheet metal workers and painting technicians, and we are confident in our construction techniques.
We are capable of handling large-scale roof projects such as factories!
5. Warranty and Aftercare
In addition to the manufacturer’s warranty, solar panel installation work comes with our own construction warranty (leakage warranty)!
(The construction warranty for solar panel installation is 10 years. Depending on the condition of the roof before installation, we may not be able to provide a warranty unless a roof renovation is performed. The construction warranty is separate from the manufacturer’s product warranty, and the scope and conditions vary based on the warranty details.)
Aftercare is available annually, 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.
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 the solar panels decreases due to dirt, we can provide cleaning services using specialized brushes.
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 Easy-to-Understand Materials and Simulations
Kakeru Koumuten provides not only “estimates,” “layout diagrams,” and “power generation simulations” but also a “solar construction guidebook” and “profit and loss simulations” that take into account loan interest rates and electricity costs.
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 outline important points and disadvantages!
We encourage you to obtain comparative estimates and compare them with other companies’ plans!
Roof Inspection Before Installing Solar Panels
Once solar panels are installed, they will remain on the roof for 20 or 30 years.
Confirming whether it is safe to install them directly on the current roof 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 Year of Construction | The fixing method varies depending on the roofing materials such as slate, tiles, metal roofs, and flat roofs (roof waterproofing). If the remaining lifespan of the roofing material is short, we may suggest roof renovation first. |
| 2. Condition of Substrate and Waterproof Sheet | If the underlayment or roofing (waterproof sheet) beneath the roofing material is damaged, it can affect the fastening strength and waterproofing. We will also check for any signs of leaks. |
| 3. Orientation, Slope, and Shadows of the Roof | The orientation and slope of the roof surface, as well as shadows from neighboring houses, trees, and utility poles, can affect power generation. We will create a layout diagram from the drawings and the site, and you can confirm 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. The number of panels that can be installed varies depending on the size of the panels, so we will compare based on the total output of the roof. |
| 5. Fixing Method and Waterproofing Details | We will check whether the method involves drilling holes in the roofing material for fastening or using brackets to secure the roofing material. The fixing method varies by construction method, so please confirm the waterproofing treatment of the fixing parts at the time of estimation. |
| 6. Weight of the Roof | The roof will become heavier due to the panels being installed. 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 also affects the cost. |
| 8. Ease of Scaffolding Setup and Delivery Route | If there are elevation differences on the site, planning for scaffolding and the delivery route for equipment and materials may require some ingenuity. The width of the front road and any steps on the site will also be checked during the site survey. |
Fixing Methods and Confirmation Points 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 significant, 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 lighter roofing materials before installation. |
| Metal Roof (Horizontal and Vertical) | Fixed with catch-type brackets that grip the roof material (depends on the combination of roof material and brackets) | Compatibility of roof material and brackets, 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 plan to renovate the roof 10 to 20 years after installation, there will be additional costs for removing and reinstalling 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 Arakawa Ward, Tokyo
Potential Subsidies and Grants Available in Arakawa Ward, Tokyo
If you are introducing solar panels or storage batteries in Arakawa Ward, Tokyo, there is a possibility that the systems from the “National Government,” “Tokyo Metropolitan Government,” and your local Arakawa Ward may apply.
The following is based on information confirmed on the official pages of each system as of October 6, 2026. The application status may change depending on the budget, 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 “Home Solar Power Generation Promotion Project” | Individuals, corporations, or management associations installing unused solar power systems (under 50kW output, JET certification, etc.) in residential properties within Tokyo. The generated power must be used in the residential part. Pre-application is required | Existing homes: 15,000 JPY per kW for up to 3.75kW (maximum 450,000 JPY), 12,000 JPY/kW for over 3.75kW and under 50kW New homes: 12,000 JPY/kW for up to 3.6kW (maximum 360,000 JPY), 10,000 JPY/kW for over 3.6kW |
For the fiscal year 2026, pre-applications are being accepted from May 29 (will end once the budget is reached). From the pre-application for fiscal year 2026, submission of certificates issued by financial institutions during performance reporting is mandatory |
| Tokyo “Home Battery Installation Promotion Project” | Owners of eligible devices (batteries registered with SII) excluding national and local governments. Must be installed between April 1, 2026, and March 30, 2027. If applying after October 1, 2026, only products registered with the national SII for fiscal year 2026 are eligible | Battery package: 100,000 JPY per kWh (maximum 1,200,000 JPY per household) Additional for participating in DR demonstration (100,000 JPY per unit; 150,000 JPY per unit if energy management devices are installed) Battery unit expansion: 60,000 JPY/kWh (maximum 720,000 JPY per household) |
For the fiscal year 2026, pre-applications are being accepted from May 29. Grant applications and performance reports will be accepted from June 30 |
| Arakawa Ward “Fiscal Year 2026 Eco Subsidy Project (Solar Power Generation System & Battery System)” | Individuals, multi-family housing, or businesses installing systems in residences where they are registered as residents in the ward. Must not be in arrears on special ward taxes, metropolitan taxes, or national health insurance premiums. Applications must be made after installation and payment are completed (within one year from the completion date) | Solar power generation: 20,000 JPY per kW (maximum 300,000 JPY for local contractors, 250,000 JPY for non-local contractors) Battery system: 5,000 JPY per kWh (maximum 150,000 JPY for local contractors, 100,000 JPY for non-local contractors) |
Applications will be accepted from May 1, 2026, to February 26, 2027, during the application period (60% of the budget as of September 25, 2026). Applications will close once the budget is reached |
| National “DR Home Battery Project” (Fiscal Year 2025 Supplement) | Newly introducing home battery 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) | As of May 29, 2026, the budget has been reached, and the public offering has ended (there are no plans to reopen the public offering as stated on the official website, and applications cannot be made at this time) |
| National “Mirai Eco Housing 2026 Project” (Renovation) | Batteries are one of the eligible facilities, but they must be combined with essential works such as insulation renovations of windows (openings) and structures; applications cannot be made for battery installation alone. Solar panels are not included as eligible facilities | Battery: 96,000 JPY per household | As soon as the budget limit is reached, it will end. As of October 5, 2026, the application amount for renovations is displayed as 8% of the budget on the official website. Please check the reception status on the official website. |
The Tokyo solar power and storage battery subsidies require prior application. For storage batteries applied for after October 1, 2026, only products registered with the national SII will be eligible, and the equipment requirements will change. The subsidy in Arakawa Ward is a system where applications are made after installation, construction, and payment are completed, and application documents must be submitted within one year from the installation completion date and within the reception period (by February 26, 2027). Eligibility conditions, application procedures, and the possibility of combining different systems vary, and applying does not guarantee that subsidies will be granted, so please confirm before contracting and starting work.
At Kakeru Koumuten Co., Ltd., we will guide you on the eligibility conditions and application periods for each system after confirming them.
National Subsidy “DR Home Storage Battery Project (Support Project for Introducing Home Storage Systems for DR Resource Implementation)”
The government has been implementing the “DR Home Storage Battery Project” to support the installation of home storage batteries.
This project targets those who are newly introducing registered storage systems that can be utilized for demand response (DR), and in the fiscal year 2025 supplementary budget, the subsidy amount was determined based on a standard amount of 34,500 JPY per initial effective capacity of 1 kWh, with a subsidy rate of up to 30% and a maximum of 600,000 JPY per application. There are conditions such as that contracts or orders made before the grant decision are not eligible.
However, the fiscal year 2025 supplementary budget reached its application amount on May 29, 2026, and the public recruitment has ended. The official website also states that there are currently no plans to reopen public recruitment, and applications cannot be made at this time. Please check the official website for future public recruitment.
Additionally, there are currently no subsidies confirmed for the installation of solar panels for existing homes.
👉 Click here for the official website of the DR Home Storage Battery Project
Tokyo “Promotion Project for Introducing Solar Power Generation in Homes”
This subsidy is for those who are installing a new, unused solar power generation system in residential homes in Tokyo. The simultaneous installation of storage batteries is not a condition.
● Existing homes: For systems under 3.75 kW, 150,000 JPY per kW (maximum 450,000 JPY); for systems over 3.75 kW and under 50 kW, 120,000 JPY per kW.
● New homes: For systems under 3.6 kW, 120,000 JPY per kW (maximum 360,000 JPY); for systems over 3.6 kW and under 50 kW, 100,000 JPY per kW.
● Additional amounts are available for the installation of rooftop frames and waterproofing work.
The target is to install unused panels with an output of less than 50 kW that have obtained JET certification, used in the living area of residential homes in Tokyo. The process involves making a prior application and then applying for the grant after installation; from the fiscal year 2026 prior application, submission of a certificate issued by a financial institution during the performance report is now mandatory.
The official page of Tokyo states that pre-registration is being accepted from May 29, Reiwa 8. It will end once the budget is reached, so please check the official page for the registration status.
👉 Here is the official page of Tokyo (Cool Net Tokyo)
Tokyo’s “Household Battery Installation Promotion Project”
This is a subsidy for the installation costs of battery systems aimed at increasing self-consumption of electricity generated by solar power and improving energy independence during emergencies.
●Battery package: 100,000 JPY per kWh (up to 1,200,000 JPY per household)
●Additional for participating in DR demonstration: 100,000 JPY per unit (150,000 JPY per unit if energy management equipment is installed)
●Expansion of battery units: 60,000 JPY per kWh (up to 720,000 JPY per household)
Eligible applicants are owners of the subsidized equipment (excluding national and local governments), and installation must occur between April 1, Reiwa 8, and March 30, Reiwa 11. If pre-registration is done after October 1, Reiwa 8, only products registered with the national SII for Reiwa 8 will be eligible.
The official page of Tokyo states that pre-registration is being accepted from May 29, Reiwa 8. For details such as conditions for combination with solar power generation, please check the official page.
👉 Here is the official page of Tokyo (Cool Net Tokyo)
Arakawa Ward “Reiwa 8 Eco Subsidy Project (Solar Power Generation System and Battery System)”
This is a subsidy for those who install solar power generation systems and battery systems in residential areas within the ward. Applications are to be made after installation, construction, and payment are completed, not before the work. If purchased and installed from contractors within the ward, the upper limit is set higher than for contractors outside the ward.
●Solar power generation: 20,000 JPY per kW (upper limit is 300,000 JPY for contractors within the ward and 250,000 JPY for those outside)
●Battery system: 5,000 JPY per kWh of storage capacity (upper limit is 150,000 JPY for contractors within the ward and 100,000 JPY for those outside)
For individuals, it is required that the installation is done in a residence where they are registered as a resident and actually living, and they must not be in arrears on special ward taxes, metropolitan taxes, or national health insurance premiums. The subsidy only covers the cost of the equipment itself (excluding consumption tax), and discounts or points/coupons are not included. Each subsidy item can be applied for only once, and application documents must be submitted within one year from the completion date of installation and within the application period (until February 26, Reiwa 9). Whether a contractor is within the ward is determined by the address of the issuer of the receipt and breakdown.
The official page of Arakawa Ward states that the application period for Reiwa 8 is from May 1, Reiwa 8, to February 26, Reiwa 9, and as of September 25, Reiwa 8, 60% of the budget has been applied for. Applications will close once the budget is reached, so please check the official page for the latest application status.
👉 Here is the official page of Arakawa Ward
Solar Panel Installation and Battery Installation Price List
⇧Service Menu | For Costs Related to Solar Panel and Battery Installation, Click Here
⇧Service Menu | For Costs Related to Solar Panel Removal and Water Heater Removal, Click Here
Breakdown of Installation Capacity, Equipment, and Construction Costs
The costs for solar panels and batteries should be confirmed by separating them into “Equipment Costs (Device Costs)” and “Construction Costs.”
Even for the same “Complete Solar Panel Installation,” the amount can vary significantly depending on the installation capacity, equipment grade, and roof condition.
Considerations for Installation Capacity (kW) and Battery Capacity (kWh)
The installation capacity of solar panels is determined by “Output of One Panel (W) × Number of Panels”, with the unit being kW (kilowatts). Batteries are compared based on the amount of electricity they can store, represented in kWh (kilowatt-hours).
The amount of kW that can be installed on a roof varies for each house based on the roof’s shape, orientation, and size. At Kakeru Koumuten, we create layout diagrams from blueprints and on-site surveys to present the installation capacity.
On our pricing page, we list solar panels priced between 800,000 JPY and 1,200,000 JPY for 3-5 kW, and between 1,200,000 JPY and 1,900,000 JPY for 6-10 kW. (These are just estimated amounts and may vary based on factors such as wiring length, scaffold range, existing roofing materials, and panel layout.)
▶ Installation Menu | Costs for Solar Panel Installation and Battery Installation
Items to Confirm in the Estimate (Cost Confirmation)
When comparing estimates, it is common to compare different capacities and equipment based solely on price. 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 specified. |
| 2. Power Conditioner | Manufacturer, model number, capacity, number of units, installation location (indoor/outdoor). Also check if it is a type that controls in conjunction with the battery. |
| 3. Battery | Manufacturer, model number, capacity (kWh), range usable during power outages (entire house or specific circuits), installation location. |
| 4. Mounting Frame and Fittings | Name of fittings suitable for the roofing material and method of securing (whether it is a method that drills holes or a method that clamps and secures). |
| 5. Wiring and Electrical Work | Wiring route and length, work around the distribution board, presence of a monitor to check power generation. |
| 6. Roof Reinforcement and Waterproofing | Details of waterproofing treatment at the 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 it is simultaneous with roofing work or exterior painting, check that the same scope and quantity are not double-counted. |
| 9. Removal and Disposal | Whether the removal of existing solar thermal water heaters or old panels and disposal costs for waste materials are included. |
| 10. Tax Classification and Warranty | Whether 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. welcome comparisons, so if you bring estimates from other companies, we will explain the differences for each item!
Self-Estimate and Profit Simulation for Solar Power Generation
With the simulator above,
you can get an estimated quote and a profit and loss simulation for up to 30 years!
If you know the total installation capacity of solar panels on the roof and the capacity of the storage battery, you can obtain an estimated quote and profit and loss simulation!
*The simulation results are estimates. Actual profits and losses may vary based on assumptions such as electricity rates, self-consumption ratios, selling prices, and costs for equipment inspection and replacement.
Customer Feedback
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customer reviews
Asao-ku, Kawasaki City | We received reviews about the ridge cap and rain gutter replacement work!
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customer reviews
Kohoku-ku, Yokohama | We received reviews about the roof overlay (cover method)!
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customer reviews
Kohoku-ku, Yokohama | We Received Reviews About Exterior Painting!
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customer reviews
Hodogaya-ku, Yokohama | We received reviews about our exterior fence construction!
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customer reviews
Tsurumi-ku, Yokohama | We received reviews about roof and exterior wall painting, as well as metalwork and rain gutter replacement work!
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customer reviews
Higashiyamato City, Tokyo | We received reviews about exterior painting and roof overlay (cover method)!
Examples 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 and Waterproofing Arrangement |
| Fixed using catch type hardware to grip the horizontal metal roof (Catch Method) |
| Price Range |
| 2,200,000 JPY～2,300,000 JPY *Due to the grant being provided, the actual burden amount is approximately 1,000,000 JPY Estimated recovery period for construction costs: about 8 to 9 years (self-consumption) *The grant amount and recovery estimates are based on the system and calculations at the time of construction, and may differ under the current system. |
| Construction Period |
| Approximately 3 days |
| Completion Month |
| April 2025 |
| Inquiry Details |
| I am considering the installation of solar panels and storage batteries. I heard that grants are available, and I would like to know how much will be provided. |
Our Proposal
We visited to provide an estimate and created a layout diagram for the solar panels from the drawings!
The layout diagram shows the configuration of the 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 grant amount, so we explained it to the customer along with the estimate!
How to Choose a Solar Panel Installation Contractor in Arakawa, Tokyo
There are many solar panel installation contractors available in Arakawa Ward, Tokyo, and you may be unsure which contractor to choose.
Therefore, when requesting solar panel installation and battery storage installation work, let’s check the following 4 points.
● Have extensive knowledge not only about solar panels but also about roofs
● Confirm the presence of warranties and aftercare services
● Obtain estimates from multiple contractors (3 companies as a guideline)
● Check if they provide support for subsidy applications
By confirming the above 4 points, you will be able to choose a reliable contractor.
Knowledge about roofs as well as solar panels
Defective installation of solar panels can sometimes be caused by a lack of knowledge and verification regarding roofs and waterproofing.
While knowledge about solar panels is certainly important, understanding the roof and waterproofing at the installation site of the solar panels is also crucial.
⚠︎Examples of troubles caused by insufficient verification of roofs and waterproofing
・Solar panels installed on a deteriorated roof causing leaks
・Solar panels installed on a roof with a short lifespan, requiring removal and renovation within a few years
・Misjudgment of the type of waterproofing leading to incorrect treatment and subsequent leaks
and more.
When installing solar panels, understanding the condition and type of the existing roof allows you to avoid unnecessary expenses and unforeseen troubles.
▶ Go to “Roof Verification Before Installing Solar Panels” in this article
Confirm the presence of warranties and aftercare services
When choosing a solar installation contractor, make sure to check for warranties. It is important to confirm not only the duration of the warranty but also the coverage, exclusions, and cost conditions.
Solar panels and battery storage units come with manufacturer warranties, but also check for the presence of installation warranties in case leaks occur after installation!
If the contractor has an installation warranty, they may cover any leaks that occur after installation within the warranty period and conditions.
Additionally, some contractors offer aftercare services separate from warranties, so be sure to check if the contractor you are considering has aftercare services.
Since abnormalities and damages on the roof can be in unseen areas, you may not notice them yourself.
By conducting inspections during aftercare, you can easily detect abnormalities early, preventing major repairs or failures!
At Kakeru Koumuten Co., Ltd., the installation of solar panels comes with a leak warranty as part of the workmanship warranty. (The warranty for solar panel installation is 10 years, and depending on the condition of the roof before installation, we may not be able to provide the warranty without performing roof renovations.)
We also provide aftercare maintenance, sending out annual DM!
After checking the DM, if you wish, we will visit you for aftercare maintenance!
Obtain estimates from multiple contractors (3 companies as a guideline)
When requesting the installation of solar panels, let’s obtain estimates from multiple contractors.
Even for the same manufacturer and the same construction details, costs may vary, and warranties and after-sales services may differ.
Additionally, obtaining multiple estimates makes it easier to negotiate prices.
To request your preferred contractor at a lower price, we recommend obtaining estimates from multiple contractors.
When comparing estimates,
check the following:
「Confirmation of estimate items」
「Types of solar panels」
「Warranties and after-sales services」
and make detailed comparisons to make your decision! Avoid judging solely based on cost, as using lower-grade materials or skipping processes can reduce costs!
▶ 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 the installation of solar panels and storage batteries, but if you make mistakes in the order of procedures or if there are deficiencies in the documents, you may not receive the subsidy.
Since there are systems that require prior application, such as the Tokyo Metropolitan subsidy, it is reassuring to have a contractor who can support you with the preparation of necessary documents and the flow of procedures.
Complete the procedures specified for each system (for the Tokyo Metropolitan subsidy, prior application is required) before proceeding with the construction!
For the Tokyo Metropolitan subsidy, after installation, you will need to submit a subsidy application and performance report, which will be reviewed before the subsidy is granted! (The flow of procedures varies by system)
▶ Go to “Subsidies and grants that may be applicable in Arakawa Ward, Tokyo” in this article
Benefits of Introducing Solar Equipment
The benefits of introducing solar panels are as follows!
Benefit 1: Economic Benefits
The biggest advantage of introducing solar panels is the economic benefit!
The selling price of electricity has decreased compared to ten years ago, but by consuming the generated electricity, you can reduce the amount of electricity purchased from the utility company and gain benefits!
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!
For residential use (under 10kW), the selling price (FIT) from certifications after October 2025 will be set at “24 yen/kWh for the first four years, and 8.3 yen/kWh from the fifth to the tenth year.” 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) rather than sell it, making the combination with a storage battery a viable option.
👉 Ministry of the Environment | For purchase prices and periods, click here
Advantage 2 Subsidies can be utilized!
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 through subsidies is a significant advantage!
In Arakawa Ward, you may be eligible for programs from the national government, Tokyo Metropolitan Government, and Arakawa Ward (please check the application status for each program).
Advantage 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 like power conditioners may have operational noise.)
Advantage 4 Heat insulation effects are expected!!
By installing the panels on the roof or rooftop, they block direct sunlight from hitting the roof.
Especially in summer, this can help suppress the rise in roof temperature, providing a heat insulation effect!
（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 becomes possible to use electricity even during emergencies such as power outages!
Even without a storage battery, if you have a power conditioner with autonomous operation capability, you may be able to use electricity from a dedicated outlet during daytime generation.
（The devices, output, and duration that can be used during a power outage vary depending on the model and wiring method）
What points should be noted when introducing solar power generation?
Next, we will explain the “three points to note” when installing solar panels!
Point 1 Maintenance costs can be incurred
A particularly overlooked maintenance cost is for the roof where solar panels are installed.
If you perform roof renovations 10 to 20 years later, there will be costs for removing and reinstalling the solar panels.
If the existing roof is deteriorated, it is reassuring to renovate it with durable roofing materials before installing the solar panels!
Additionally, there will be costs for regular inspections of the equipment, repairs or replacements of the power conditioner, and updates due to the deterioration of the storage battery.
It would be reassuring to consider maintenance costs in simulations before introducing solar panels!
Point 2 The risk of leaks increases depending on the roofing material
The fixing methods for slate roofs and tile roofs vary by construction method, but in methods that fix brackets to the roofing material or substrate with screws, waterproofing of the fixed parts 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, replacing the roofing material with a metal roof and fixing the solar panels using the catch method is also an option. (The catch method has compatibility conditions between the roofing material and brackets, and cannot be used with all metal roofs)
Catch-type base metal fittings for horizontal metal roofs
Note 3: The roof will become heavier
Since solar panels will be installed, the roof will become heavier. After investigating the existing roof, substrate, and load capacity, switching to 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 by Total Output of the Roof
When installing solar panels on the roof, it is important to know how much power can be generated in a limited area, and generating more power is always better!
Solar panels vary in size and output depending on the manufacturer.
A panel with an output of 350W and a panel with an output of 400W 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 one 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 is a calculation of total output (kW). The actual power generation (kWh) will vary depending on conditions such as roof orientation, slope, and shading.
Choosing Method 2: Compare by Degradation Rate of Solar Panels
Solar panels have a degradation rate, and their output gradually decreases over 10 years and 20 years.
The degree of output reduction after long-term use varies by product. The manufacturer’s output guarantee value is a standard figure for warranty purposes and does not indicate the actual degradation rate or power generation itself.
Choosing solar panels while considering the degradation rate will help avoid regrets!
Choosing Method 3: Compare by Warranty Period
There are several types of warranties for solar panels, including “output warranty,” “natural disaster warranty,” and “system warranty,” and the warranty periods vary by manufacturer.
Regarding the output warranty, some manufacturers offer a 30-year warranty while others provide a 10-year warranty, so it varies widely!
It’s better to have a longer warranty, so let’s check the warranty periods and conditions of the manufacturers you are considering!
Frequently Asked Questions about Solar Power and Storage Battery Installation in Arakawa, Tokyo
We have compiled frequently asked questions from customers considering the installation of solar panels and storage batteries in Arakawa, Tokyo. (Tap to open the answers)
How much does it cost to install solar panels and storage batteries in Arakawa, 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.
For cost estimates by capacity, please refer to the solar panel installation and storage battery installation pricing page. We will create a layout diagram from the drawings and on-site survey and provide a free estimate!
Are there any subsidies available for solar power and storage battery installation in Arakawa, Tokyo?
As of October 6, 2026, Tokyo’s “Household Solar Power Generation Promotion Project” (for existing homes, 15,000 yen per kW for up to 3.75kW, with a maximum of 450,000 yen) and “Household Storage Battery Promotion Project” (100,000 yen per kWh, with a maximum of 1.2 million yen per household) are accepting pre-applications starting May 29, Reiwa 8, as listed on the official Tokyo website (Cool Net Tokyo). In Arakawa, the Eco Subsidy Project (for solar power generation, 20,000 yen per kW with a maximum of 300,000 yen for local contractors and 250,000 yen for outside contractors; for storage systems, 5,000 yen per kWh with a maximum of 150,000 yen for local contractors and 100,000 yen for outside contractors) is accepting applications from May 1, Reiwa 8, to February 26, Reiwa 9, as stated on the official Arakawa website. The national DR household storage battery project has ended its public recruitment.
Since the application status may change, please refer to the subsidy and grant section and consult us before signing a contract.
Can I apply for subsidies after the construction is completed?
It depends on the system. Tokyo’s subsidies require pre-application. Conditions such as whether you can contract and start construction before applying vary by system, so please check before signing a contract.
The order of procedures varies by system, so 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 method of securing the panels varies by construction method, and when securing brackets to the roofing material and 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 after 10 to 20 years of 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 through a site survey!
Should I install a storage battery together with the solar panels?
If you want to use the generated electricity at night or prepare for power outages, simultaneous installation is recommended. The selling price for electricity will be 8.3 yen/kWh after the fifth year, making it more advantageous to use it in your home rather than selling it.
Additionally, the subsidy for storage batteries in Tokyo (for the fiscal year Reiwa 8, it is 100,000 yen per kWh, with a maximum of 1.2 million yen per household) is aimed at increasing self-consumption of electricity generated by solar power. In Arakawa Ward, storage systems are also included in the subsidy program (V2H compatible products are also eligible). You can compare “solar only” and “solar + storage battery” in a financial simulation for your consideration.
How many kW can be installed on my roof? Is it okay for north-facing roofs or those 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 from the drawings and site survey, and provide you with the installation capacity and power generation simulation.
Arakawa Ward is an urban area with a mix of residential, commercial, and industrial buildings, and there are many small residential lots, so the shape, orientation of the roof, and the shading from surrounding buildings will differ from house to house. 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 depending on whether roofing work is done simultaneously and the shape and installation capacity of the roof.
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 (under 10 kW), the selling price will be 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 fiscal year 2026.
The idea is to recover initial costs more quickly in the first four years and then focus on self-consumption. Kakeru Koumuten provides a financial simulation that takes into account loan interest rates and electricity costs.
Can you handle maintenance and inspections after installation?
Yes, we can. Kakeru Koumuten sends out annual after-maintenance DM notices and visits customers who wish to have inspections. We can also clean solar panels with a special brush if the power generation decreases due to dirt.
Since it is difficult to check areas on the roof by yourself, please feel free to consult us if you have any concerns.
Can you also renovate 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 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 Arakawa, Tokyo, please consult Kakeru Koumuten
Our company handles many exterior renovations, including solar panels, roof work, and exterior wall work in Arakawa, 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 great feedback from numerous customers.
We continue to update our construction performance every year, and we will strive to improve quality to satisfy even more customers in the future.
Our company can perform all exterior renovations, not only roof overlay (cover method) and re-roofing, but also partial roof repairs, exterior painting, and exterior wall cover methods.
We are also happy to handle small jobs such as partial repairs and rain gutter cleaning!
In urgent cases such as leak repairs, we may be able to provide temporary measures without setting up scaffolding, as long as safety can be ensured, so please consult us!
“I want to know about recommended solar panels”, “I want to keep costs down as much as possible”, “I just want an estimate for now”, we will provide optimal solutions for specific requests.
We will never propose unnecessary work that prioritizes profit!
We always stand in the customer’s position and propose the best construction plan!
We are confident that we will not lose in terms of cost, quality, and organization compared to other companies in exterior construction!
We welcome competitive quotes because we are confident!
Estimates are completely free, and if our company is found to be inferior to others, you are free to decline!
Characteristics of Arakawa, Tokyo and Points of Solar Construction
Arakawa Ward has a total area of 10.16 square kilometers, making it the 22nd largest among the 23 wards. It is located in a region bordered by the northeastern edge of the Musashino Plateau and the Sumida River, with lowlands except for a slight area of plateau in the southwestern part. We have summarized the characteristics of the terrain in Arakawa Ward, Tokyo, and points to consider when installing solar panels and storage batteries below. (Tap to open)
View the characteristics of Arakawa Ward, Tokyo, and points for solar construction
■ Flat lowlands and plateau in the southwestern part. Check scaffolding, delivery, and shadows for each site
Most of the ward is flat, with a part of the Yamanote Plateau in the southwestern area, and elevated areas known as Suwadai and Dokanyama. The ward has many urban areas where residential, commercial, and industrial buildings are mixed, as well as many small residential lots. In sites where buildings are close together, the shadow cast by neighboring houses, the space for scaffolding, and the delivery routes for equipment vary from house to house. At Kakeru Koumuten, our own scaffolding team plans the scaffolding according to the site, creates layout diagrams from blueprints and on-site surveys, and you can confirm this with a power generation simulation.
■ Flooding of the Arakawa River is expected to cause prolonged inundation. Check the installation location of equipment
According to the ward’s public relations, it is anticipated that most of the ward will be inundated for a long time if the Arakawa River floods. Depending on where the power conditioner and storage batteries are installed, separate from the panels on the roof, the impact during flooding may vary. Please check the inundation assumptions for your residence on the ward’s “Arakawa Ward Disaster Prevention Map (Flood Version)” and consult with us about the installation location and height in conjunction with the installation conditions of the manufacturer you are using.
■ The types and ages of roofs vary from house to house. Check the roof and waterproofing before installation
Even within the same ward, the types of roofs, their ages, and the shapes of the lots vary from house to house. At Kakeru Koumuten, we will check the type and condition of the roof and the situation of the lot before installation and propose methods for securing, waterproofing details, and scaffolding planning.
■ The annual sunshine hours at the Tokyo Observatory is about 1,927 hours
According to the Japan Meteorological Agency’s average values (1991-2020), the annual sunshine hours at the Tokyo Observatory is about 1,927 hours, with January (about 193 hours) having the most and June during the rainy season (about 124 hours) having the least. (This is a reference value, not an observation value within Arakawa Ward.)
The power generation amount in Arakawa Ward can also change due to shadows from surrounding buildings, so conducting a year-round power generation simulation and selecting the capacity of the storage battery according to the times of high electricity usage are key points.
Our company handles many exterior construction and solar projects in Arakawa 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 Arakawa Ward, Tokyo
Kakeru Koumuten Co., Ltd. accepts requests for work throughout Kanagawa Prefecture and Tokyo.
List of Areas in Arakawa Ward, Tokyo
Arakawa, Arakawa Ward / Nishiogu, Arakawa Ward / Nishinippori, Arakawa Ward / Higashiogu, Arakawa Ward / Higashinippori, Arakawa Ward / Machiya, Arakawa Ward / Minamisenju, Arakawa Ward
・For exterior wall painting in Arakawa Ward, Tokyo, trust Kakeru Koumuten Co., Ltd.!
・For roof renovations in Arakawa Ward, Tokyo, trust Kakeru Koumuten Co., Ltd.!
・For exterior renovations in Arakawa Ward, Tokyo, trust Kakeru Koumuten Co., Ltd.!
・Kakeru Koumuten Co., Ltd.施工実績
・Kakeru Koumuten Co., Ltd. after maintenance
・Kakeru Koumuten Co., Ltd.施工メニュー・料金表
・Kakeru Koumuten Co., Ltd. staff blog and announcements
・Explaining the importance of comparative estimates and points to consider!
・12 major manufacturers of solar power generation! Features and selection points are also introduced!
・What are the installation costs for solar power generation? Tips for reducing costs are thoroughly explained!
・What are the best locations for installing solar power generation? Points for selecting installation locations are also introduced!
・Here is the introduction to solar power generation estimates!
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contact Kakeru Koumuten Co., Ltd.
Kakeru Koumuten is a young company whose team is, on average, in their late twenties, but our skills are second to none.
Our greatest strength is that we handle scaffolding, roofing and painting entirely in-house. In an industry where these tasks are usually divided among contractors, our complete service simplifies project management and helps keep costs down. Above all, if a problem arises, we respond promptly.
We proudly describe ourselves as the youngest and most helpful renovation company in Kanagawa!
