Thailand Solar Law 2026 Overview — What Changed
2026 marks a watershed for Thai solar regulation. The Factory Act amendment eliminates the Ror.Ngor.4 license requirement for rooftop solar, dramatically cutting red tape. The ERC has restructured oversight by capacity tier, making sub-1 MW installations nearly permit-free. Royal Decree #805 offers a 1.5x tax deduction on solar equipment, while BOI Section 7.1 provides 8-year CIT exemption. Once you understand the law, use the 20-point solar procurement checklist before signing a contract. For the complete permit step-by-step guide, see our dedicated page.
Thai Solar Law Timeline
Which Laws Apply to Your Factory — Decision Matrix by Capacity
Your solar system size determines which laws and procedures apply. The table below divides into 3 tiers by generation capacity, giving you a clear overview. Most factory rooftop installations fall into Tier 1 (<1 MW) with minimal regulatory burden. Start by understanding your electricity bill structure to see where solar saves. See the comprehensive factory solar guide for more details.
| Dimension | <1 MW (Tier 1) | 1-10 MW VSPP (Tier 2) | >10 MW SPP/IPP (Tier 3) |
|---|---|---|---|
| Applicable Laws | Building Control Act, PEA/MEA interconnection rules | Energy Industry Act, ERC VSPP regulations, Building Control Act | Energy Industry Act, ERC SPP/IPP regulations, Environmental Act (EIA) |
| Required Permits | Aor.1/Aor.6 + PEA/MEA interconnection (no more รง.4) | ERC license (VSPP) + Aor.1/Aor.6 + PEA/MEA + COD | ERC license (SPP/IPP) + EIA/EHIA + EGAT PPA + Aor.1/Aor.6 + COD |
| Approving Authority | Local municipality + PEA or MEA | ERC + Local municipality + PEA/MEA | ERC + ONEP (EIA) + EGAT + Local municipality |
| Typical Timeline | 3-6 months | 6-12 months | 12-18 months |
| Key Notes | Most factory rooftops fall here — minimal process | Additional ERC license required — longer timeline | Requires EIA + EGAT PPA contract — most complex |
Factory Act Amendment — No More Ror.Ngor.4 for Rooftop Solar
Before the December 2024 Factory Act amendment, every factory wanting rooftop solar had to amend its Ror.Ngor.4 factory license to add activity category 88 (power generation) — a 30-60 day process with significant paperwork. The amendment explicitly classifies solar self-generation as NOT constituting a change in factory activity type, eliminating the รง.4 amendment requirement entirely. This is the single most impactful change for small and medium factories.
During the transition period, some local DIW officers may not yet be aware of the amendment. Reference the latest Ministry of Industry notification that explicitly states the exemption. If issues persist, contact your EPC provider (such as CapSolar) to coordinate with the authorities on your behalf.
ERC Regulations — Self-Generation, Grid Connection & Excess Sale
The Energy Regulatory Commission (ERC) regulates power generation by capacity tier: systems <1 MW for self-consumption are exempt from ERC licensing; 1-10 MW requires a VSPP (Very Small Power Producer) license; >10 MW requires SPP or IPP licensing. Grid connection depends on voltage: <69 kV connects directly to PEA/MEA, while >=69 kV must coordinate with EGAT. For factories wanting to sell excess power, apply for PEA/MEA net-metering (current buyback rate ~2.20 THB/kWh). For Thailand factory electricity tariff details, see the tariff reference page.
<1 MW: No ERC license needed
1-10 MW: VSPP license
>10 MW: SPP/IPP license
As of May 2026; subject to regulatory changes
Tax Benefits — 1.5x Deduction (Royal Decree 805) + BOI Stacking
Royal Decree #805 allows a 1.5x deduction of solar equipment investment costs against Corporate Income Tax (CIT). This stacks with BOI Section 7.1 benefits (8-year CIT exemption + 0% import duty). Additionally, factories can sell T-VER carbon credits through TGO. Calculate your factory solar ROI with our free tool. For BOI solar incentives 2026 details, see the dedicated page. Also check solar subsidies via our subsidy checker.
Worked Example: 500 kW System
Direct PPA & Third Party Access — New Pathway in 2026
Direct PPA allows renewable energy producers to sell electricity directly to consumers via the PEA/MEA/EGAT transmission grid, paying a wheeling charge of approximately 1.07 THB/kWh. In 2026, ERC has launched a Direct PPA pilot with a total capacity of 2,000 MW. For more details, see the Direct PPA complete guide. Read What is PPA for PPA fundamentals and PPA vs EPC comparison to understand the differences between models.
From Law to Installation — Quick-Reference Flowchart
The law-to-installation path summarized in 7 steps, from system sizing to grid energization. Timeline estimates: 3-6 months (<1 MW), 6-12 months (VSPP), 12-18 months (SPP). Analyze your factory electricity bill to see how much you could save. For solar panel prices Thailand 2026, see the latest pricing update.
Determine Your Tier
Refer to the Decision Matrix above — system size determines your tier
Confirm รง.4 Exemption
Self-consumption systems no longer need รง.4 amendment per the Factory Act revision
Apply for PEA/MEA Connection
Prepare single-line diagram + factory documents, submit to PEA or MEA
Apply for Building Permit (Aor.1/Aor.6)
Submit structural load drawings + modification plans to local municipality
If VSPP: Apply for ERC License
For 1-10 MW systems, apply for an additional VSPP license from ERC
Claim Tax Benefits
File Royal Decree 805 (1.5x deduction) + BOI Section 7.1 (if applicable)
System Commissioning
Pass COD inspection + install bidirectional meter + start generating power
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