How a Thai factory's electricity bill is built.
A time-of-use bill has four parts: a demand charge, an energy charge, Ft and a monthly service charge, with VAT on top. This page explains what sets each one, and quotes every rate from MEA, PEA or the Energy Regulatory Commission with a link to where it was read.
Four parts. One of them is priced on a single moment.
The energy charge and Ft count kilowatt-hours. The demand charge counts kilowatts, once a month, at your worst moment. The service charge is fixed.
Demand charge
Set by your highest 15-minute average in the month's on-peak hours.
Energy charge
Every unit you buy, at an on-peak or an off-peak rate depending on when.
Ft
An adjustment on every unit, set by the ERC every four months.
Service charge
A fixed monthly amount, plus power factor and VAT where they apply.
Your size decides your tariff type.
MEA serves Bangkok, Nonthaburi and Samut Prakan, and PEA the rest of the country. Each publishes its own schedule, and their rates for factories are the same. What differs is how each names its voltage bands. Your bill states your type and your voltage.
| Tariff type | Who it is for | Demand charge | Time of use |
|---|---|---|---|
| Type 2 · Small general service | Highest 15-minute demand under 30 kW | None | Optional (2.2) |
| Type 3 · Medium general service | 30 kW to under 1,000 kW, and no more than 250,000 kWh a month averaged over the previous three months | Yes | TOU (3.2). The normal rate, 3.1, is only for sites already on it: before October 2000 at MEA, November 2015 at PEA |
| Type 4 · Large general service | 1,000 kW and over, or more than 250,000 kWh a month averaged over the previous three months | Yes | TOU (4.2). Time of day, 4.1, is only for sites already on it: before October 2000 at MEA, November 2015 at PEA |
From MEA's and PEA's tariff schedules. A site that joined type 3 or 4 after November 2015 is on time-of-use, wherever it is.
One 15-minute interval sets it for the month.
Your meter averages your demand over every 15 minutes. On a time-of-use tariff the demand charge is priced per kilowatt of the highest of those averages in the month's on-peak hours, so a single short spike can set it for thirty days.
| MEA voltage | PEA voltage | Demand charge, ฿/kW a month |
|---|---|---|
| 69 kV and over | 69 kV and over | 74.14 |
| 12–24 kV | 22–33 kV | 132.93 |
| Below 12 kV | Below 22 kV | 210.00 |
Rates 3.2 and 4.2, the same at MEA and PEA, excluding Ft and VAT. Off-peak demand is not charged. Minimum charge: the bill cannot be lower than 70% of the highest demand charge in the last 12 months, ending in the current month, so one high peak can set a floor under your bill for a year.
Time of day (TOD) works differently, and is closed to new sites.
Only large users already on 4.1, before October 2000 at MEA or November 2015 at PEA, are on it. Demand is charged every day in two windows: peak, 18:30–21:30, at 224.30, 285.05 or 332.71 ฿/kW, and partial peak, 08:00–18:30, on only the demand above the peak window's, at 29.91, 58.88 or 68.22 ฿/kW, from the highest voltage band to the lowest. Off-peak demand is free, and energy is one flat rate.The same kilowatt-hour costs more on a weekday afternoon.
On-peak is 09:00 to 22:00, Monday to Friday. Off-peak is 22:00 to 09:00 on those days, and all day on Saturdays, Sundays, Labour Day and ordinary public holidays. Two exceptions catch people out: a compensatory holiday stays on-peak, and so does Royal Ploughing Day when it falls on a weekday.
| MEA voltage | PEA voltage | On-peak, ฿/kWh | Off-peak, ฿/kWh | Gap, ฿/kWh |
|---|---|---|---|---|
| 69 kV and over | 69 kV and over | 4.1025 | 2.5849 | 1.5176 |
| 12–24 kV | 22–33 kV | 4.1839 | 2.6037 | 1.5802 |
| Below 12 kV | Below 22 kV | 4.3297 | 2.6369 | 1.6928 |
Rates 3.2 and 4.2, the same at MEA and PEA, excluding Ft and VAT. The gap is on-peak less off-peak, worked out from the two quoted rates; it is what arbitrage earns on each unit before round-trip losses.
Ft moves every four months, on every unit.
Ft is a per-kWh adjustment added to the base energy rate on every Thai electricity bill. The Energy Regulatory Commission sets it every four months, to pass changes in fuel and power-purchase costs through to customers. It is the same on an on-peak unit as on an off-peak one.
16.23 satang/kWh
Set by the ERC on 22 July 2569, excluding VAT, and the same as May–August. On the base tariff of 3.78 ฿ a unit it makes an average of 3.95 ฿ a unit. The ERC put the period's fuel and power-purchase cost at 41.27 satang a unit and used 25.04 satang of clawed-back funds to bring Ft down to 16.23, so a later period may be higher.
Three smaller lines, and VAT.
Service charge
312.24 ฿ a month at every voltage, at MEA and PEA alike, on top of the minimum charge where that applies.
Power factor
When your highest 15-minute reactive demand is more than 61.97% of your highest 15-minute real demand, each kVAR over it costs 56.07 ฿.
Minimum charge
No lower than 70% of the highest demand charge in the last 12 months, so one bad peak can set a floor under your bill for a year.
VAT
Every rate on this page excludes it. It is added to the bill on top of the rates and Ft.
One more rule for sites with their own transformer: if the meter sits on its low-voltage side, PEA adds 2% to the billed kW and kWh to cover the transformer's losses.
Not every line on the bill is in reach.
A battery changes when you buy power, and a battery with solar changes how much. Which lines that touches follows from how each one is set.
Yes, directly
Covering the highest on-peak interval lowers the charge for the month. Peak shaving
Yes, two ways
Buying off-peak to use on-peak earns the gap, and stored solar replaces units you would have bought. Arbitrage
Only with fewer units
Moving a unit from off-peak to on-peak does not change how many you buy, so it saves no Ft. Stored solar that replaces grid units does.
No
It is fixed per meter, whatever you use and whenever you use it.
Where every figure on this page comes from.
Tariffs change, and Ft changes three times a year. Each figure above is quoted from one of these, with the date the organization last updated it. Your own bill is the final word on your site.
| Source | What it gives | Updated |
|---|---|---|
| PEA · อัตราค่าไฟฟ้า, September 2026 | The binding Thai schedule: types 2 to 4, TOU and TOD rates, minimum and power factor charges, the TOU timetable, VAT. Effective from the September 2026 bill, which changed residential rates only | 22 Aug 2026 |
| PEA · Electricity Tariffs, May 2023 | PEA's unofficial English translation of the schedule before, still the one its English site lists; its factory rates match the September 2026 schedule figure for figure | 25 Oct 2024 |
| PEA · Latest Ft | Ft of 0.1623 ฿ a unit (its page still labels it May–August 2026) | 28 Nov 2025 |
| MEA · Type 4, large general service | Type 4: eligibility, TOD and TOU rates at MEA's voltage bands, minimum and power factor charges, the TOU timetable, VAT. Effective from the January 2023 bill | 9 Jan 2023 |
| MEA · Type 3, medium general service | Type 3: eligibility, normal and TOU rates, and when a site moves to type 2 or 4 | 9 Jan 2023 |
| MEA · Ft, September–December 2026 | MEA's clarification of 27 July 2026: 0.1623 ฿ a unit, excluding VAT, the same as May–August | 27 Jul 2026 |
| ERC · Ft, September–December 2569 | The decision itself: meeting 29/2569 on 22 July 2569, Ft 16.23 satang a unit, base tariff 3.78 ฿, average 3.95 ฿, excluding VAT | 23 Jul 2026 |
Updated is the date each organization gives: the page's last-updated date where it shows one, otherwise the date on the document. For MEA's tariff sheets it is the date MEA saved the file.
See these lines on your own bill.
Twelve months of billing data, and we will model your load, size the system and show you the whole financial case, including when the answer is not to build.
Or reach us at solarbuddies@pjjsolutions.tech