Installing solar rooftop legally in Thailand involves four steps: a building-modification permit (Or.1) from the local authority, registration with the Energy Regulatory Commission (ERC) as an energy business exempt from licensing, an application to the Metropolitan or Provincial Electricity Authority (MEA/PEA) to connect, and final inspection and meter change by the utility. Requirements depend on system size.
How Does System Size Affect the Permit?
Permit criteria are based on installed PV capacity, in three bands:
| Band | Installed PV capacity |
|---|---|
| 1 | Below 200 kWp |
| 2 | 200 kWp up to 1,000 kWp |
| 3 | 1,000 kWp and above |
For the residential rooftop programme (category 1, homes), capacity was limited to 10 kWp, with surplus power bought back at 2.2 baht per unit for 10 years at the time of the original article (2023). Homes outside the programme may install more than 10 kWp. Programme terms change, so check the current rules before applying.
The 4 Permit Steps
1. Building Permit (Or.1) from the Local Authority
Apply to the local authority (municipality or subdistrict office) for permission to modify the roof structure before installation.
- Application form, plans showing the roof layout and structure, the panel support structure and installation details
- Structural calculations, building survey form, and certification by the civil engineer who designs and supervises the work
Installation can start once the local authority’s approval is received.
2. Register with the ERC
Notify the Office of the Energy Regulatory Commission that you operate an energy business exempt from licensing (at the ERC office or online).
- Copy of the local authority’s acknowledgement
- Photos of the complete panel array and inverter
- Single-line diagram signed by a power engineer
- Installation structure plans and structural calculations signed by a civil engineer
- Panel and inverter type, model, brand and specification (the inverter must be registered with, or meet the standard of, the utility)
- Copy of ID matching the electricity account name, electricity bill, and power of attorney if applicable
3. Apply to MEA or PEA
Register to join the buy-back programme or to request parallel connection through the utility’s website (MEA or PEA). PEA applicants not joining the buy-back programme submit documents to their local PEA office.
- Application form and roof layout/structure plans
- ID of the electricity user and the account (CA) number from the bill
- Panel and registered inverter specifications
- Single-line diagram certified by an engineer, with a copy of the engineer’s licence
- Site map, photo of the front of the building, and photos showing every panel
Under the residential programme, a single-phase meter allowed up to 5 kW and a three-phase meter up to 10 kW.
4. Utility Inspection and Connection
After the ERC and MEA/PEA steps are approved, pay the service fees and, if joining the programme, sign the power purchase agreement. The utility inspects the internal wiring and generating system, replaces the meter with a solar meter, and connects the system (COD). The on-grid system can then start operating.
Why Install Legally?
- Safety and reliability: compliant installation reduces technical and accident risks.
- Maximum performance: correct installation lets the system produce as much energy as possible.
- Eligibility for support: legally installed systems can qualify for government support or benefits.
How ONVALLA Handles It
ONVALLA provides a complete solar rooftop service: consulting, site survey, system design, installation, permit applications, system inspection and after-sales service, for on-grid, off-grid and hybrid systems, using Tier 1 panels and inverters and equipment that meet international standards. See ONVALLA Solar Rooftop.
Frequently Asked Questions
Does an off-grid system need utility permission?
No. Off-grid systems do not connect to the utility network. See system types.
Who must sign the drawings?
A civil engineer certifies the structure and a power engineer certifies the single-line diagram.
Contact ONVALLA to handle the permits for your project, or see our solar solutions.
