How a Thai electricity bill is built
Both utilities — the Provincial Electricity Authority (PEA, กฟภ.) and the Metropolitan Electricity Authority (MEA, กฟน.) in Bangkok, Nonthaburi and Samut Prakan — charge the same national base rates. A monthly bill is:
Energy charge + Demand charge (business types 3–7) + Service charge + Ft × units, then + 7% VAT
- Energy charge (THB/kWh) — flat, tiered, or split into on-peak and off-peak.
- Demand charge (THB/kW) — for medium and large users, on the highest 15-minute average power.
- Service charge (THB/month) — fixed.
- Ft — the automatic fuel adjustment, revised every four months by the Energy Regulatory Commission. It changes too often to print here; check the current Ft on the PEA website.
Which type are you?
| Type | Who | Size rule |
|---|---|---|
| 1 | Homes, temples and places of worship | — |
| 2 | Small business, offices, government | Peak demand below 30 kW |
| 3 | Medium business and industry | 30–999 kW, and ≤ 250,000 kWh/month (3-month average) |
| 4 | Large business and industry | ≥ 1,000 kW, or > 250,000 kWh/month |
| 5 | Specific business — hotels and lodging | ≥ 30 kW |
| 6 | Non-profit organisations | — |
| 7 | Agricultural water pumping | — |
| 8 | Temporary supply | — |
On-peak and off-peak hours
TOU (types 1.2, 2.2, 3.2, 4.2, 5.1, 6.2, 7.2)
- On-peak: Monday–Friday, 09:00–22:00.
- Off-peak: Monday–Friday, 22:00–09:00, and all day on Saturday, Sunday and normal public holidays (substitution holidays are not included).
- Peak: 18:30–21:30.
- Partial: 08:00–18:30 (demand charged only on the amount above the peak-period demand).
- Off-peak: 21:30–08:00.
Medium and large business TOU — the rate most factories pay
Types 3.2 (medium) and 4.2 (large) have identical rates. The same figures apply to 5.1 (hotels, TOU), 6.2 (non-profit, TOU) and 7.2 (agricultural pumping, TOU), except that 7.2 has a service charge of 204.07 THB/month.
| Voltage | Demand, on-peak (THB/kW) | On-peak energy (THB/kWh) | Off-peak energy (THB/kWh) | Service (THB/month) |
|---|---|---|---|---|
| ≥ 69 kV | 74.14 | 4.1025 | 2.5849 | 312.24 |
| 22–33 kV | 132.93 | 4.1839 | 2.6037 | 312.24 |
| < 22 kV | 210.00 | 4.3297 | 2.6369 | 312.24 |
Minimum charge (types 3 and 4): the monthly bill cannot be lower than 70% of the highest demand charge of the past 12 months, including the current month. This matters mainly in months when a plant is shut down.
Metering on the low-voltage side: if the meter sits on the low-voltage side of a customer-owned transformer, kW and kWh are increased by 2% to cover transformer losses.
Normal (non-TOU) rates — 3.1 and 5.2
Type 3.1 is only for customers who were already on it before November 2015 (they may move to 3.2, but cannot move back). Type 5.2 is a temporary rate for hotels that do not yet have a TOU meter.
| Voltage | 3.1 Demand (THB/kW) | 3.1 Energy (THB/kWh) | 5.2 Demand (THB/kW) | 5.2 Energy (THB/kWh) |
|---|---|---|---|---|
| ≥ 69 kV | 175.70 | 3.1097 | 220.56 | 3.1097 |
| 22–33 kV | 196.26 | 3.1471 | 256.07 | 3.1471 |
| < 22 kV | 221.50 | 3.1751 | 276.64 | 3.1751 |
Large business TOD — 4.1 (legacy)
Only for customers who were already on 4.1 before November 2015.
| Voltage | Peak demand (THB/kW) | Partial demand (THB/kW) | Off-peak demand | Energy (THB/kWh) |
|---|---|---|---|---|
| ≥ 69 kV | 224.30 | 29.91 | 0 | 3.1097 |
| 22–33 kV | 285.05 | 58.88 | 0 | 3.1471 |
| < 22 kV | 332.71 | 68.22 | 0 | 3.1751 |
Residential and small business
Type 1.1 — homes, normal rate (tiered):
| Units per month | 1.1.1 (≤ 150 kWh/month) | 1.1.2 (> 150 kWh/month) |
|---|---|---|
| First 15 | 2.3488 | — |
| 16–25 | 2.9882 | — |
| 26–35 | 3.2405 | — |
| 36–100 | 3.6237 | — |
| 101–150 | 3.7171 | — |
| First 150 | — | 3.2484 |
| 151–400 | 4.2218 | 4.2218 |
| Over 400 | 4.4217 | 4.4217 |
| Service charge (THB/month) | 8.19 | 24.62 |
| Type | Voltage | On-peak (THB/kWh) | Off-peak (THB/kWh) | Service (THB/month) |
|---|---|---|---|---|
| 1.2.1 | 22–33 kV | 5.1135 | 2.6037 | 312.24 |
| 1.2.2 | < 22 kV | 5.7982 | 2.6369 | 24.62 |
| 2.2.1 | 22–33 kV | 5.1135 | 2.6037 | 312.24 |
| 2.2.2 | < 22 kV | 5.7982 | 2.6369 | 33.29 |
Other types: non-profit normal rate 6.1 — 3.4149 (≥ 69 kV) and 3.5849 (22–33 kV) THB/kWh, service 312.24; below 22 kV the first 10 kWh cost 2.8013 and the rest 3.8919, service 20.00. Agricultural pumping 7.1 — first 100 kWh 2.0889, the rest 3.2405, service 115.16. Temporary supply (type 8) — 6.8025 THB/kWh.
Worked example — a factory on 3.2.2 (22–33 kV)
A plant with a highest on-peak 15-minute demand of 500 kW, using 120,000 kWh on-peak and 60,000 kWh off-peak in the month:
| Item | Calculation | THB |
|---|---|---|
| Demand charge | 500 kW × 132.93 | 66,465.00 |
| On-peak energy | 120,000 kWh × 4.1839 | 502,068.00 |
| Off-peak energy | 60,000 kWh × 2.6037 | 156,222.00 |
| Service charge | 312.24 | |
| Subtotal before Ft and VAT | 725,067.24 |
Power factor: if the highest 15-minute reactive demand exceeds 61.97% of the highest demand (a power factor below about 0.85), every kvar above that costs 56.07 THB. In this example, anything above 310 kvar would be charged.
What this means for solar and battery storage
- Solar reduces on-peak units. Solar generates mostly inside the 09:00–22:00 weekday on-peak window, so each kWh used on site saves about 4.1839 THB plus Ft. Weekend and holiday generation saves only the off-peak rate, which matters for plants that run seven days a week.
- Solar alone cannot be relied on to reduce the demand charge. The demand charge follows the highest 15 minutes of the month. One cloud during the plant's peak, or a peak after sunset, sets demand as if there were no solar. Reducing it reliably needs a battery that discharges at the peak — see how to cut a factory's demand charge with peak shaving.
- Every 100 kW of demand reduced saves 13,293.00 THB a month at 22–33 kV, as long as the reduction holds for every on-peak 15-minute window in the month.
- Shifting load is worth 1.5802 THB/kWh (on-peak minus off-peak at 22–33 kV). That is the margin for a battery charged off-peak and discharged on-peak, before losses.
FAQ
What are the TOU on-peak hours in Thailand?
Monday to Friday, 09:00–22:00. Off-peak is 22:00–09:00 on weekdays and all day on Saturday, Sunday and normal public holidays; substitution holidays count as normal days.How is the demand charge calculated?
The meter records average power in every 15-minute interval. The highest 15-minute average during the month's on-peak period, in kW, is multiplied by the demand rate — for example 132.93 THB/kW at 22–33 kV. Off-peak demand is not charged on TOU.What is Ft?
Ft is the automatic tariff adjustment for fuel and power-purchase costs. It is added per kWh to every bill, is set by the Energy Regulatory Commission and changes every four months.What is the difference between types 3 and 4?
Type 3 is for users from 30 kW up to 999 kW with no more than 250,000 kWh a month; type 4 is for users of 1,000 kW or more, or over 250,000 kWh a month. On TOU (3.2 and 4.2) the rates are the same.Does MEA charge different rates from PEA?
No. The base rates are the same nationwide. MEA uses 12–24 kV and below-12 kV voltage bands and some different sub-type numbers.Can solar panels reduce the demand charge?
Sometimes, but not reliably. The demand charge follows the highest 15-minute average of the month, and a cloud or an evening peak sets it regardless of solar. A battery that discharges during the peak is what makes the reduction dependable.What is the 70% minimum charge?
For types 3 and 4, the monthly bill cannot be lower than 70% of the highest demand charge in the past 12 months. It mostly affects months with little or no production.Are these rates current?
They are PEA's base rates effective from the May 2023 bill, which PEA still publishes as its current tariff (checked September 2026). Ft is separate and changes every four months.Summary
Most Thai factories pay type 3.2 or 4.2 TOU rates: 132.93 THB/kW demand plus 4.1839 THB/kWh on-peak and 2.6037 THB/kWh off-peak at 22–33 kV, plus Ft and VAT. The on-peak energy charge is what solar reduces. The demand charge, set by one 15-minute window a month, is what a battery controls.