Zero Export (no backfeed)
The inverter or controller throttles PV output in real time so net flow at the grid meter never goes negative — no backfeed at all. This is the default for most C&I factories.
Energy Policy
Zero Export for Thai Factory Solar No-Backfeed Rules — MEA/PEA Compliance 2026
Why most Thai factory rooftop solar must not feed power back into the grid — transformer-based reverse-flow thresholds, the reverse-power-flow protection device (Zero Export Controller vs Reverse Power Relay 32), MEA/PEA approved lists, and 5 FAQs for factories and businesses.
Transformer ThresholdsController vs Relay 32MEA/PEA Lists + FAQ
~11 min read
Regulatory data as of Jun 2026
Grid-connection requirements, approved-equipment lists, and technical thresholds reference current ERC announcements and MEA/PEA service pages. PEA requirements may differ from MEA in detail. Always confirm with your local utility and a licensed design engineer before proceeding. This information supports decision-making and is not engineering or legal advice.
Quick Answer — What Is Zero Export Solar in Thailand?
In Thailand, commercial & industrial (C&I) rooftop solar is normally configured for self-consumption only and typically must prevent electricity from flowing back ("exporting") into the PEA/MEA grid when installed capacity is large relative to the distribution transformer's rating. In that case the utility generally requires a reverse-power-flow protection device — either a Zero Export Controller or a Reverse Power Relay (commonly referenced by the ANSI device code 32) — and the device should be on the utility's approved list and pass inspection. The exact reverse-flow threshold varies by utility and connection; confirm it with your local PEA/MEA office. MEA explicitly classifies this service as "generate for own use, no electricity sales to MEA."
Wondering if you can sell surplus back and at what rate? See Net Billing vs Net Metering Thailand
What "Zero Export" / "Export Limit" Means
Both terms describe controlling solar so power does not flow back into the utility grid — they differ only in the threshold they enforce.
Export Limit (capped)
The same mechanism as zero export, but set to a non-zero ceiling (for example, matching the capacity registered with the utility). The Thai term for this class of equipment is "อุปกรณ์ป้องกันไฟฟ้าไหลย้อน" (reverse-power-flow protection device).
Why it exists
To protect distribution-network stability — and because it blocks backfeed, it inherently adds a layer of anti-islanding behavior, preventing power injection into the grid during a utility outage.
The Regulatory Reality in Thailand
This is the core section — who regulates, what the default rule is, and how the 15% transformer rule works.
Who regulates?
The Energy Regulatory Commission (ERC / กกพ) is the sector regulator under the Energy Industry Act B.E. 2550 (2007). MEA (Metropolitan Electricity Authority, Greater Bangkok) and PEA (Provincial Electricity Authority, the rest of Thailand) are the distribution licensees that run the actual interconnection / parallel-connection approval.
The default = self-consumption, no sale
MEA's official parallel-connection service for self-generators is explicitly "no sale to MEA." For most C&I, there is no active scheme to be paid for exported surplus — the residential net-billing buy-back (~2.20 THB/kWh) is residential-focused and quota-limited, not a general C&I export route. See the Net Billing vs Net Metering page for current rates and quota details.
The 15% transformer rule
When aggregate generator capacity on one distribution transformer is large relative to that transformer's kVA rating, the reverse-power-protection device requirement is generally triggered. Industry practice commonly references a figure of around 15% of the transformer rating as the trigger point, but the actual threshold varies by utility, voltage level, and connection. Both MEA and PEA apply comparable parallel-connection / no-sale regimes — always confirm the exact reverse-flow limit with your local PEA/MEA district office before design.
2024 licensing relaxation (context, not an export rule)
A Ministerial Regulation effective 28 Dec 2024 removed the need for an ERC factory license for solar rooftop installations outside industrial estates, regardless of capacity. This eased permitting, but did not change the export / self-consumption reality.
Zero Export Controller vs Reverse Power Relay (32)
Once over the 15% threshold, MEA/PEA accept either of two compliant paths — pick one. Both must pass utility inspection.
Zero Export Controller
Usually simpler to approve if the device is already on MEA's approved list — submit the datasheet, CT spec, and application form. Install cost is typically lower when pre-approved equipment is used.
Reverse Power Relay (32)
Heavier documentation — single-line diagram, schematic with CT & VT calculations, and a relay setting table with calculations. The reverse-power setpoint is an engineering value, not a number fixed in regulation; a common engineering rule of thumb is to set it at the lower of roughly 5% of the transformer rating or roughly 10% of installed PV capacity — but verify the required setpoint with your utility and your inverter/relay vendor.
Approval lists matter
MEA maintains an official Zero Export Controller approved-device registry and an inverter approval list; PEA maintains its own inverter approval list. Use only listed devices to avoid rejection. Listed inverters generally align with international anti-islanding standards (IEC 61727 / IEC 62116), but the utility's published list is the binding reference.
What Zero-Export Means for Your Factory's Numbers
Good news: for most factories, zero-export barely dents ROI — because the nature of factory load already works in your favor.
Why it's usually fine for factories
Daytime industrial/commercial load typically absorbs PV output directly, so a well-sized system exports little anyway. Zero-export caps the waste — it does not cap the savings you earn on every self-consumed kWh.
The design lever — sizing & load matching
Size to daytime load. Consider load-shifting or a battery to raise the self-consumption ratio when a zero-export cap would otherwise clip midday generation. Use the Solar ROI Calculator and Bill Analyzer to find the right size.
No feed-in revenue ≠ bad ROI
Because the C&I buy-back route is effectively closed, the economic case rests on offsetting the retail tariff you avoid, not on selling surplus. See Net Billing vs Net Metering for the buyback-rate mechanics and Net Metering Thailand for the policy overview.
Compliance Checklist for a Thai C&I Project
Six steps to plan a factory solar project that passes utility inspection.
1. Confirm your utility
Determine whether the site falls under MEA (Greater Bangkok) or PEA (elsewhere) — the approved-equipment lists and inspection processes differ.
2. Compare kW to transformer kVA & ask the utility for the limit
Compare installed capacity (kW) against your distribution transformer's kVA rating, and ask your local utility for the exact reverse-flow limit (industry practice commonly references around 15% of the transformer rating as the trigger, but the real figure varies by utility and connection). If you meet the condition, a reverse-power-protection device is required.
3. Specify Controller or Relay 32 from the approved list
If over threshold, specify a Zero Export Controller OR a Reverse Power Relay 32 from the utility's approved list — pick one.
4. Use an inverter on the approved list
Choose an inverter on the MEA/PEA approved list, which generally aligns with international anti-islanding standards (IEC 61727 / IEC 62116). For interconnection engineering, see Grid Interconnection & Transformer.
5. File the parallel-connection application and pass inspection
Submit the parallel-connection (and VSPP, where applicable) application, and pass utility inspection before energizing. If you're weighing power-purchase structures, see What Is a PPA.
6. Document everything for inspection
Keep the single-line diagram (SLD), datasheets, and relay setting tables ready for the utility's inspection.
About the Author
This article is prepared by Frank Lee, Founder of CapSolar, with experience in solar EPC and grid interconnection for factories and businesses in Thailand. Regulatory information references official MEA/PEA service pages, ERC announcements, and real CapSolar project experience.
Reviewed by: CapSolar Research Team | Updated: Jun 2026
Frequently Asked Questions
Sources
- Metropolitan Electricity Authority (MEA) — Generator Paralleling Service (15% transformer rule / reverse-power protection device / generate for own use, no sale)
- MEA — official Zero Export Controller approved-device registry and inverter approval list; Provincial Electricity Authority (PEA) — inverter approval list
- Energy Regulatory Commission (ERC) — Energy Industry Act B.E. 2550 (2007) and the rooftop-solar licensing-relaxation Ministerial Regulation (effective 28 Dec 2024)
Need Your Factory Solar to Pass MEA/PEA Compliance?
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