Thai factory electricity costs 4.10-5.50 THB/kWh effective (including Ft 0.1623 + VAT) for May-Aug 2026, depending on tariff category (Cat 3 medium / Cat 4 large), time-of-use period (on-peak/off-peak), and demand charge — significantly higher than the residential average of 3.95 THB/kWh.
Factory vs Residential — 3 Key Differences
Many assume factory electricity is billed like residential. In reality, industrial tariffs (Cat 3/4/5) are far more complex than residential (Cat 1) — with hidden costs that make factory bills much higher than expected.
Factory (Cat 3-4) | Residential (Cat 1) | |
|---|---|---|
| Demand Charge | Yes — 74-210 THB/kW (15-min peak) | None |
| TOU Mandatory | Cat 4 mandatory / Cat 3 optional | Optional (most use flat) |
| PF Penalty | 56.07 THB/kVAR if below threshold | None |
| Energy Rate (On-Peak) | 4.10-4.33 THB/kWh | ~3.95 THB/kWh (avg) |
| Effective Cost/kWh | 4.10-5.50 THB (incl. demand + PF) | ~4.15 THB (incl. Ft + VAT) |
Factory Tariff Tables: Cat 3/4/5 (May-Aug 2026)
Rates below are base rates (excluding Ft and VAT) per ERC announcement — current Ft = 0.1623 THB/kWh, VAT 7% on total.
Flat Rate — Voltage < 22 kV
TOU — Voltage < 22 kV
TOU — Voltage 22-33 kV
What Is Demand Charge — Why Factory Bills Are High
Demand charge is a cost based on the peak power (kW) your factory draws during on-peak hours — measured as the highest 15-minute average demand in any billing period, not the actual energy (kWh) consumed.
Demand charge can account for 20-30% of total factory electricity bill — even if peak usage lasts just minutes, you pay for that peak all month.
Example: 500 kW demand factory
500 kW x 210 THB/kW = 105,000 THB/month in demand charges alone — before any energy (kWh) costs.
How solar reduces demand: Solar produces maximum power during 10:00-14:00, exactly when on-peak demand is highest — directly reducing peak grid demand and saving both kWh and demand charges.
Power Factor Penalty — The Hidden Factory Tax
Power Factor (PF) measures how efficiently your factory uses electricity — if PF falls below the threshold, the utility charges a penalty surcharge.
Example: Factory with PF 0.75 (low)
Active 400 kW, Reactive 350 kVAR → exceeds by 102 kVAR → penalty = 102 x 56.07 = 5,719 THB/month — large factories can pay 50,000+ THB/month in PF penalties.
How to Fix Low PF
- Install capacitor banks — instant fix, ROI under 1 year
- Modern solar inverters can provide partial PF correction
How to Read a Factory Bill — 5 Key Components
Factory electricity bills are far more complex than residential — 5 main components that managers must understand to find savings.
5 Proven Ways to Cut Factory Bills
Electricity is one of the top operating costs for Thai factories — but there are proven ways to cut 10-60% depending on your situation.
1. Switch to TOU (if still on flat)
5-15%Factories with high night/weekend usage can save 5-15% by switching from flat to TOU — off-peak rates are nearly half.
2. Peak Shaving to Cut Demand Charge
10-25%Stagger heavy equipment startups — reduces 15-min peak significantly, saving 10-25% on demand charge.
3. Fix PF with Capacitor Banks
100% penalty cutLow investment (ROI < 1 year), eliminates PF penalty 100% — large factories save 50,000+ THB/month.
4. Energy Efficiency Upgrades
10-20%LED lighting, VFD motors, chiller optimization — cuts kWh usage 10-20% with moderate investment.
5. Install Rooftop Solar — The Biggest Lever (30-60%)
30-60%Solar cuts factory bills multiple ways: (1) direct kWh savings during on-peak, (2) reduces grid peak demand = lower demand charge, (3) no fuel/Ft cost, (4) BOI tax benefits — total savings 30-60% of electricity bill.
Worked Examples: 3 Factory Sizes
Examples below use actual May-Aug 2026 rates (including Ft 0.1623 + 7% VAT) to show real factory electricity costs by size.
FAQ
Data Sources
- Energy Regulatory Commission (ERC)
- Metropolitan Electricity Authority (MEA) — Tariff Schedule
- Provincial Electricity Authority (PEA) — Tariff Schedule
- EGAT — Ft Announcement
Data reference period: May-Aug 2026
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