Rooftop solar power after Decree 243/2026: How to design it so that the investment doesn't need revisions?

Decree 243/2026/ND-CP opens up more opportunities for rooftop solar power exploitation for production facilities. However, favorable policies do not mean that businesses can install them immediately without reassessing the project.

For an already operational factory, adding a solar power system too late into the design can generate a host of additional work: structural inspection, roof reinforcement, electrical panel replacement, transformer substation adjustments, cable reorganization, and handling of roof penetrations.

For newly constructed factories, integrating solar power systems right from the design stage will help investors better control costs, minimize modifications, and maintain the potential for future expansion.

What changes does Decree 243/2026 bring?

On June 26, 2026, the Government issued Decree 243/2026/ND-CP, amending some provisions of Decree 57/2025/ND-CP and Decree 58/2025/ND-CP related to the mechanism for direct electricity trading and the development of renewable and new energy sources. View the document on the Government's Electronic Information Portal..

A notable point is that the percentage of surplus electricity from self-produced and self-consumed rooftop solar power systems can be negotiated for purchase up to 50% of the electricity generated at the inverter's output. In some cases, up to December 31, 2030, this percentage may be higher if the power system is capable of receiving and meeting safe operating requirements. Summary of information from EVN.

The new regulations make investment more attractive, especially for power plants with large roof areas and stable load profiles. However, the percentage of electricity purchased, the connection method, and the procedures applied still depend on each project, the grid's capacity, and the agreement between the parties.

Businesses should view the new mechanism as a condition for developing investment plans, not as a reason to skip the survey and technical design process.

Why is installing solar panels after a factory is completed often expensive?

Many factory buildings were previously designed based solely on loads serving the roof structure, MEP systems, and routine maintenance. When solar power is added, the building must now handle additional loads from:

• Solar panels and support frames.
• Rails, clamps, bolts, and connection points.
• Cable trays, wires, and electrical equipment.
• Maintenance walkways and the load capacity of operating personnel.
• The impact of wind on the entire battery system.
• Local loads at the anchor point or equipment placement location.

If the roof's load-bearing capacity is insufficient, the business may need to reinforce the purlins, steel frame, or change the solar panel placement. If the location of electrical equipment is not planned, the wiring may have to be routed around, through the production area, or occupy operating space.

The cost of rework isn't just about materials. Partial shutdown of the production line, obtaining construction permits, implementing safety controls on the roof, and adjusting existing systems can directly impact production schedules.

1. Inspect the structure before finalizing the installation capacity.

The desired power output should not be the sole data point for determining the number of solar panels. First, the design team needs to survey the existing conditions and determine the actual load-bearing capacity of the structure.

For existing factory buildings, the original design documents need to be compared with the current state. Changes such as adding technical systems, installing equipment, repairing the roof, or structural corrosion can all distort the initial assumptions.

The following information should be checked:

• Load-bearing diagram of the frame and purlin system.
• Regular load and current service load.
• Additional load for the solar power system.
• The suction and lifting effects of wind at the mid-roof, roof edges, and roof corners.
• Load-bearing capacity at connection points.
• The condition of corrosion, sagging, or deformation of the structure.
• Access and load capacity for maintenance.

The survey results will help determine suitable installation areas, appropriate placement densities, and reinforcement needs. This will also serve as a basis for businesses to compare energy benefits against renovation costs.

If the plant is in the design phase, solar load should be incorporated into the structural model from the outset. This approach is often much more cost-effective than reinforcing the structure after completion.

2. Don't let your solar power system become the cause of roof leaks.

Waterproofing is one of the common risks when installing solar panels on factory roofs. Drilling holes through the roof panels, improper connections, or damage to the protective coating can create leaks and corrosion.

The design proposal needs clarification:

• The solution involves connecting the solar panel frame to the roof system.
• Anchoring location and requirements to limit penetration through the roof.
• How to apply waterproofing material at the joint.
• The thermal expansion and contraction between the roof, support frame, and solar panels.
• The gap between the solar panels and the roof surface allows for heat dissipation.
• Space for cleaning gutters and inlets.
• Accessibility is important when roof panel replacement is needed.

The placement of the solar panels must also not obstruct the drainage of water. Leaves, dust, and construction materials can accumulate in hard-to-reach areas, increasing the risk of waterlogging and roof degradation.

For coastal environments or areas with chemical vapors, the corrosion resistance of the support structure, connections, and equipment must be considered. The use of different materials must also be evaluated to limit electrochemical corrosion.

3. Integrate electrical architecture from the outset.

A solar power system does not operate independently of the factory's electrical system. The installed capacity needs to be compared with the load profile, transformer substation capacity, main switchboard, and current operating mode.

The design team needs to coordinate the following elements:

• Location of inverter and switchgear.
• DC and AC cable lines.
• Cooling space, equipment inspection and replacement.
• The receiving capacity of the substation and switchgear.
• Safe protection, isolation, and switching solutions.
• Grounding and lightning protection system.
• Methods for measuring and monitoring production output.
• Ability to integrate with generators, ATS, and power factor correction systems.
• Spare space is available for expanding or adding storage systems.

If these issues are only addressed after the solar panels have been installed, the business may have to change cable routes, relocate equipment, or upgrade the electrical cabinets unexpectedly.

Conversely, integrated design allows for the selection of power capacity that closely matches actual usage needs. The plant can prioritize self-consumption, then assess the amount of surplus electricity and determine the appropriate power delivery and reception plan.

4. Coordinate fire safety and roof accessibility.

Solar power generates electricity when sunlight is present. Therefore, power source isolation, rescue, and firefighting measures need to be considered right from the design stage.

The battery site must maintain access for inspection and troubleshooting. Technical areas, roof access, switchgear locations, and fire access routes should not be obstructed.

The file should clearly show:

• Partitioning the solar panel clusters.
• Technical access ramp on the roof.
• Isolation and system switching locations.
• Labels identify the power source and cable route.
• Distance from smoke exhaust, ventilation and special areas.
• This plan is coordinated with the factory's overall fire prevention and control solution.

Specific requirements must be checked based on the nature of the project, legal documentation, and guidance from the competent authority at the time of implementation. Businesses should not use a single configuration for all factories.

5. How can construction be carried out without disrupting production?

With the plant in operation, the installation process can affect multiple areas simultaneously. Work on the roof creates risks of falling objects, dust, noise, and potential impact on products or equipment below.

Before construction begins, it is necessary to determine:

• Accessible area.
• Time may be needed to isolate the power system.
• Construction is divided into phases.
• Work at height techniques and fall control.
• Procedures for controlling heat-generating work processes.
• A plan to shield the production area.
• Testing, power-on, and handover plan.

For plants requiring continuous operation, the construction solution should be divided into independent zones. Work requiring power outages can be scheduled during maintenance periods or outside of production hours.

This approach is similar to the DATA Cons principle analyzed in the article. Renovating an existing factoryDesign and construction methods must begin with the requirement to maintain the business's operations.

6. Prepare for storage systems and future needs.

Decree 243/2026 also clarifies the role of storage systems in rooftop solar power models. However, even without investing in battery storage in the initial stages, businesses should still anticipate the possibility of adding it later.

A "scalability-ready" plan might include:

• Space allocated for storage devices and auxiliary systems.
• Cable or conduit line.
• The scalability of the electrical cabinet.
• Communication backup and monitoring systems.
• Ventilation, cooling, and fire safety plan.
• Access area for transporting, installing, and maintaining equipment.

This mindset is also relevant to preparing factory infrastructure for supply chain shifts and new production requirements. Investors can refer to this for further information. Factory design checklist in the China+1 trend.

The three-step process limits revisions.

Step 1: Survey and establish input data

Collect structural, architectural, electrical, fire protection, and load diagram documents. For existing buildings, survey the roof, load-bearing structure, drainage system, and actual electrical equipment.

Step 2: Integrated Design

The structural design, roof architecture, MEP, fire protection, and operational plan are integrated into a single model. System capacity is selected based on load-bearing capacity, consumption needs, and connection conditions, not solely on roof area.

Step 3: Construction, testing, and handover

Deployment should be carried out in zones, with safety controls in place and minimal impact on production. Handover documentation must accurately reflect equipment location, cable routes, protection parameters, isolation instructions, and maintenance plans.

Checklist for investors

Before deciding to invest in rooftop solar power for their factory, businesses should answer at least 10 questions:

1. Are the roof structure completion documents complete and consistent with the current situation?
2. Is the structure capable of withstanding additional loads and wind impacts?
3. Does the bonding method affect waterproofing and roof warranty?
4. Are drainage systems and maintenance areas kept clear?
5. Are the substation, switchgear, and protective equipment capable of handling the load?
6. Does the cable route affect production, internal traffic, or emergency evacuation?
7. Have grounding, lightning protection, and power source isolation solutions been implemented?
8. Does the battery site ensure adequate access and meet fire safety requirements?
9. Does the construction work require stopping the production line or cutting off the power?
10. Can the system be scaled up or have storage integrated in the future?

Conclude

Decree 243/2026 provides further impetus for businesses to exploit rooftop solar power. However, the effectiveness of the investment still depends on the ability to integrate the system with buildings, power systems, and production activities.

The best approach is to assess solar power potential right from the factory design stage. For existing buildings, a thorough survey is necessary before finalizing the capacity and signing an installation contract.

DATA Cons can coordinate the review of the structure, roofing, MEP, fire protection, and construction plan to ensure the solar power system is seamlessly integrated with the factory. See more information. DATA Cons' industrial design and construction solutions or Contact DATA Cons to discuss specific needs.

Note: The legal content in this article is for reference only. Each project requires checking the regulations, procedures, and requirements of the competent authorities at the time of implementation.