Complete comparison of two surplus selling models — 2.20 THB buyback rate, ROI impact analysis, self-consumption optimization, VSPP/SPP surplus selling, and 10 detailed FAQs for homes and factories.
Electricity rates, buyback rates, and policies reference ERC and PEA/MEA announcements as of May-Aug 2026 and may change with ERC review cycles. Numerical calculations are estimates for decision support. Consult a professional before investing.
Thailand uses Net Billing, not Net Metering — surplus solar exported to the grid is bought back at the wholesale rate of 2.20 THB/kWh, not the retail rate of ~3.95 THB/kWh. This means self-consumption is always more valuable than exporting. For factories, no surplus selling is allowed (self-consumption only); residential can sell via Solar Prachachon program up to 10 kW. Self-consumption optimization through load shifting and battery storage is the single most important ROI lever under net billing.
See the full policy overview at Net Metering & Net Billing Thailand Guide
Both systems aim to give solar owners value for surplus electricity sent to the grid, but they calculate that value fundamentally differently — which directly impacts ROI and system design decisions.
Net metering offsets electricity unit-for-unit (kWh) at the retail rate — export 1 kWh to the grid, use 1 kWh free later. Like 'depositing' electricity with the utility and 'withdrawing' it later. Used in USA, Japan, Australia (some states).
Net billing offsets financially (THB) at the wholesale/avoided-cost rate — export earns 2.20 THB/kWh but grid import costs ~3.95 THB/kWh. Separate import/export metering. Used in Thailand, Philippines, and some EU markets.
| Dimension | Net Metering | Net Billing (Thailand) |
|---|---|---|
| Offset method | kWh-for-kWh | Financial credit (THB) |
| Export rate | = Retail rate (3.95 THB) | 2.20 THB/kWh (wholesale) |
| Loss per kWh exported | 0 THB | -1.75 THB vs self-use |
| Meter type | Bidirectional (net) | Separate import/export |
| Incentive alignment | Export-neutral | Self-consumption-first |
| Typical in | USA / Japan / Australia | Thailand / Philippines / EU (partial) |
| Utility revenue impact | High (lost retail sales) | Low (pays wholesale) |
| Status in Thailand | Not adopted (on hold) | Currently active |
Why Thailand chose Net Billing: to maintain grid stability, protect utility revenue, and incentivize solar system designs that maximize self-consumption rather than oversizing to sell excess.
Thailand uses Net Billing under the Solar Prachachon program for residential users. Factories operate under self-consumption only.
Can sell surplus to PEA/MEA at 2.20 THB/kWh via Solar Prachachon Phase 2, 500 MW allocation, 10-year contract.
NO surplus selling under standard grid connection — self-consumption only. Any surplus beyond factory load is injected into the grid without compensation. Exception: register as VSPP (<10 MW) under separate ERC license.
2019 — Phase 1 pilot: Solar Prachachon first round opens
2022 — Solar Prachachon permanent enrollment opens
Dec 2024 — Factory license exemption (รง.4) for rooftop solar
2025 — Phase 2 allocation: 500 MW
2026 — Direct PPA 2,000 MW pilot launches
The 2.20 THB/kWh rate is the ERC-set avoided cost rate, reflecting wholesale energy cost excluding grid charges, demand charge, and Ft surcharge. Compared with the retail rate of ~3.95 THB/kWh (residential, May-Aug 2026), the buyback rate is only ~56% of the self-consumption value.
| Self-Consumption | Average Value/kWh | Formula | Payback Impact |
|---|---|---|---|
| 100% | 3.95 THB | 1.00 × 3.95 | Fastest |
| 80% | 3.60 THB | 0.80 × 3.95 + 0.20 × 2.20 | Good — only 9% less |
| 60% | 3.25 THB | 0.60 × 3.95 + 0.40 × 2.20 | Moderate — 18% less |
| 50% | 3.075 THB | 0.50 × 3.95 + 0.50 × 2.20 | Tipping point — starts stretching |
| 30% | 2.725 THB | 0.30 × 3.95 + 0.70 × 2.20 | Very slow — resize system needed |
Below ~50% self-consumption, payback stretches significantly. System sizing should target 70-90% self-consumption. The Ft surcharge (0.1623 THB/kWh) is NOT included in the 2.20 rate — actual retail varies by Ft period. See detailed tariff info at Thailand Electricity Tariff.
Analyze your electricity bill at Bill Analyzer Tool
Let's look at real numbers — how does net billing affect ROI compared with hypothetical net metering?
Assuming 1,200 kWh/month generation (Thailand avg 4.0 kWh/kWp/day x 10 kWp x 30 days).
| Scenario | Self-Use kWh | Export kWh | Monthly Savings | vs Net Metering |
|---|---|---|---|---|
| Net Metering (hypothetical) | 1,200 | n/a | 4,740 THB | — |
| Net Billing 70% SC | 840 | 360 | 4,110 THB | -13% |
| Net Billing 50% SC | 600 | 600 | 3,690 THB | -22% |
Most Thai factories have high daytime loads, making 70-90% self-consumption typical. At 85% SC, a 100 kW system generates ~15,000 kWh/month, self-consumes ~12,750 kWh x 4.35 THB (TOU blended industrial) = ~55,462 THB/month savings. The remaining 15% is curtailed or gifted to the grid. See full ROI analysis at Factory Solar ROI Guide. Explore Solar Financing Options for zero-upfront alternatives.
Calculate your personalized ROI at Solar ROI Calculator
This is the most actionable section of this article — under net billing, increasing self-consumption is the single best way to boost ROI. 7 proven strategies:
Move high-energy processes (compressors, chillers, EV charging) to 09:00-15:00 solar peak hours. Use smart load controllers or BMS for automated sequencing.
Size solar to match daytime base load, not peak demand. Oversizing creates uncompensated surplus (factories) or low-value export (residential).
Store midday excess for evening/night use. LFP batteries cost 12-15K THB/kWh. Battery ROI makes sense when SC < 60%. See details at Factory Battery Storage Guide.
Divert surplus to heat pumps / water heaters during solar hours. Reduces evening gas/electric water heating costs.
Schedule workplace/fleet EV charging during solar production hours. 7-22 kW chargers absorb significant surplus. See Solar + EV Charging Factory Guide.
Configure inverter to zero-export mode (factories) or limit export to registered net billing capacity (residential). Prevents uncompensated grid injection.
Install smart load controller for automated device on/off sequencing based on real-time solar production. Factories applying all seven strategies can achieve 85-95% self-consumption.
For factories wanting to sell electricity to the grid as a business, VSPP or SPP registration is required — a process completely separate from net billing.
Capacity < 10 MW. Requires ERC license. Sells to PEA/MEA under a separate PPA (NOT net billing). Tariff negotiated per project. 2-3 year application process.
Capacity 10-90 MW. BOI incentives available. Requires competitive bidding. Irrelevant for typical factory rooftop (most are 100 kW - 5 MW).
Honest assessment: the VSPP route is complex, expensive, and slow. For most factories, maximizing self-consumption + accepting some curtailment is more practical. See full regulatory details at Solar Law Thailand 2026.
Will Thailand adopt full net metering? And what other policies could change the surplus selling game?
No clear signal from ERC. The global trend is the opposite — countries that used net metering (Australia, Germany, California) are shifting to net billing as solar penetration rises. Do not plan ROI on the assumption that Thailand will switch.
If the 2,000 MW Direct PPA pilot succeeds, factories could buy renewable energy via EGAT's transmission grid — potentially bypassing net billing entirely. See Direct PPA Guide for details.
2.20 THB has been stable since program launch. ERC reviews periodically. Global trend: buyback rates typically decline as solar penetration rises. Recommendation: base ROI on self-consumption value; treat net billing as a bonus.
BOI Category 7.1 already covers BESS. Time-of-export premium (higher rate for peak export) may emerge. For ESG/CBAM compliance, see ESG & CBAM Guide.
Invest in solar for self-consumption regardless of net billing policy changes — self-consumption value is unaffected by policy. Net billing is a bonus, not the primary ROI driver.
Policy projections are based on current ERC signals and regional trends; actual changes may differ. All financial decisions should be based on current confirmed rates.
This article is prepared by Frank Lee, Founder of CapSolar, with experience in the solar and renewable energy industry in Thailand. Information references ERC announcements, PEA/MEA tariff schedules, and real CapSolar client case studies.
Reviewed by: CapSolar Research Team | Updated: May 2026
CapSolar experts help you calculate real self-consumption rates, net billing impact, and ROI for your home or factory — free consultation, no obligation.