What Are the TOU On-Peak and Off-Peak Hours?

On Peak is 09:00–22:00 on Monday–Friday. Off Peak is 22:00–09:00 on Monday–Friday, plus all day on Saturday–Sunday, National Labour Day, and regular official holidays. Royal Ploughing Day when it falls on a weekday, substitution holidays, and special holidays added by Cabinet resolution (a rule that has applied since 2023) are counted as ordinary working days.

For a factory, this means a day when the plant is closed is not always an all-day Off Peak day. What determines the outcome is the Off Peak day calendar published each year by the electricity authority, not the factory's own holiday calendar.

A Substitution Holiday When the Factory Is Closed, but the Bill Still Counts an On Peak Period

On a Monday designated as a substitution holiday, a factory shuts down its production line for the whole day under the official government calendar. When that month's bill arrives, however, the units consumed during the On Peak period that day are still counted as On Peak units, the same as on a regular working day. The Energy Regulatory Commission (ERC) notification on TOU rate periods lists three types of holiday that are not counted as all-day Off Peak, and substitution holidays are one of them.

What Are the TOU On Peak and Off Peak Hours, and Who Sets Them?

On Peak under the TOU rate exists only on Monday–Friday. The remaining hours of Monday–Friday, plus all day on Saturday–Sunday, National Labour Day, and regular official holidays, are Off Peak — but this excludes Royal Ploughing Day, substitution holidays, and special holidays added by Cabinet resolution. These periods are set by an Energy Regulatory Commission (ERC) notification, which applies to both the Provincial Electricity Authority (PEA) and the Metropolitan Electricity Authority (MEA).

The first clause of the ERC notification defines the 'period when the system has high electricity demand (Peak)' as applying only Monday through Friday. The second clause defines the 'period when the system has low electricity demand (Off Peak)' as covering Saturday, Sunday, National Labour Day, and regular official holidays for the whole day. The second clause closes with the wording 'but excluding Royal Ploughing Day, substitution holidays, and special holidays added by Cabinet resolution.' The third clause makes the ERC chairman responsible for administering the notification, with the ERC as the body that issues rulings.

PEA and MEA both apply this same set of hours to the TOU rate, so a factory under either electricity authority uses the same periods. Units the meter records during On Peak are billed at the On Peak rate, while units during Off Peak are billed at the Off Peak rate — the two are different rates. As a result, the month's energy charge depends on which period the units fall into, not on total units alone.

The PEA Off Peak day calendar carries a note stating, 'If official holidays change, the determination of Off Peak days shall follow what the Energy Regulatory Commission specifies.' For a factory owner, this means an official holiday announcement alone does not settle whether that day is Off Peak. The answer for each year is found in the Off Peak day calendar the electricity authority publishes according to the ERC's determination.

Which Types of Holiday Are Not Counted as All-Day Off Peak?

Royal Ploughing Day when it falls on Monday–Friday, substitution holidays, and special holidays by Cabinet resolution are not counted as all-day Off Peak, even when the factory is closed. This holds the same way for both PEA and MEA, and these days carry an On Peak period at the same hours as an ordinary Monday–Friday.

All three exceptions sit at the end of the second clause of the ERC notification, which is the source of the TOU rate periods for both electricity authorities. For the bill, this means units used during the On Peak period on these days are counted as On Peak units even though the production line is idle, while National Labour Day and regular official holidays remain all-day Off Peak. When setting up an annual holiday calendar, these three types of holiday should be separated from holidays that are all-day Off Peak, so that the On Peak units estimated for each month stay close to the actual bill.

Royal Ploughing Day on a Weekday Is Billed Like a Regular Working Day

Royal Ploughing Day dropped out of the Off Peak list starting in 2006, after the National Energy Policy Council (NEPC) resolved in 2005 to make National Labour Day an Off Peak day in place of Royal Ploughing Day.

Both PEA and MEA bill Royal Ploughing Day as a regular working day when it falls on Monday–Friday. Royal Ploughing Day that falls on a Saturday or Sunday is all-day Off Peak under the Saturday–Sunday rule instead. For the bill, this means units during the On Peak period on a Royal Ploughing Day that falls on a weekday are still billed at the On Peak rate, while units for the whole of National Labour Day are billed at the Off Peak rate.

Substitution Holidays: Closed Under the Government Calendar, but the Bill Still Has an On Peak Period

Substitution holidays are billed like an ordinary Monday–Friday. In PEA's 2026 Off Peak day calendar, the substitution holidays on June 1 and December 7 are not shaded as Off Peak days.

The ERC notification lists substitution holidays among the exceptions to the Off Peak period, and MEA uses the same wording in its TOU rate notification. For planning purposes, this means moving production or maintenance work to a substitution holiday does not move that period's units into Off Peak.

Special Holidays Added by Cabinet Resolution Are Ordinary Peak Days

Special holidays by Cabinet resolution have been ordinary Peak days under the TOU rate for both PEA and MEA since the ERC resolution in March 2023.

PEA's own notification on TOU periods restates that special holidays by Cabinet resolution, 'and any other days that may arise in the future, are Peak days under the TOU rate.' Meanwhile, MEA's documentation, which cites the 2023 ERC resolution, uses the same wording for the TOU rate without distinguishing by customer type. For the bill, this means a special holiday the Cabinet announces during the year does not add an Off Peak day for the factory, and units during the On Peak period on that day are billed at the On Peak rate.

Why Do Some Older Notifications Say Special Holidays by Cabinet Resolution Are Off Peak?

Those notifications were correct for the year they were issued, because special holidays by Cabinet resolution in 2021 and 2022 used to be Off Peak, before the ERC resolution in March 2023 changed them to ordinary Peak days.

For 2021, an ERC resolution in January 2021 designated that year's special holidays as 'an Off Peak period.' The special holidays of 2022 were likewise designated as 'an Off Peak period,' citing a 2020 ERC notification. Starting in 2023, the rule changed to ordinary Peak days under the ERC resolution of March 2023, and this is the rule currently in effect.

A note in PEA's Off Peak day calendar records that this resolution was made 'to reflect the electricity usage pattern of official holidays added as a special case by Cabinet resolution.' Documents, articles, or calendars produced before 2023 could therefore correctly state that special holidays were Off Peak for their own year, but that statement cannot be used to estimate the current year's bill. If it is used anyway, units on a special holiday would be estimated at the Off Peak rate, while the actual bill charges the On Peak period of that day at the On Peak rate, so the estimate would not match the bill. Before using any calendar or estimation document, check the year it was issued first, then use the current year's Off Peak day calendar directly from the electricity authority.

How Different Are the On Peak and Off Peak Rates, and Which Period Determines the Demand Charge?

For medium-sized businesses on the TOU rate, low-voltage class (category 3.2.3) with PEA, as of September 2026 the On Peak energy charge is 4.3297 THB/kWh, before the fuel adjustment charge (Ft) (in Thai) and value-added tax (VAT). The Off Peak energy charge for the same medium-sized TOU low-voltage category (3.2.3) with PEA, as of September 2026, is 2.6369 THB/kWh, before Ft and VAT.

These two figures are only an example from a single row of PEA's rate notification, because small businesses, large businesses, other voltage classes, and MEA's rates each have their own rate row. The principle that applies to every row of the TOU rate is that units used during On Peak are billed at that row's On Peak rate, and units during Off Peak are billed at that row's Off Peak rate.

The TOU rate calculates the demand charge from the peak electricity demand recorded only during the On Peak period, while the normal rate and the TOD rate calculate it from the highest demand of the whole month. This rule applies to both PEA and MEA and matches both electricity authorities' official electricity bill calculators. For the bill, this means running heavy loads together during Off Peak is not counted toward the demand charge, but the On Peak period on a substitution holiday, a Royal Ploughing Day that falls on a weekday, and a special holiday by Cabinet resolution is counted as well.

What Types of Factory Use the TOU Rate, and How Does the TOD Rate Differ?

The TOU rate is an optional rate for customer category 2, the rate for new customers in categories 3 and 4, and the rate applied to all customers in category 5 (those not yet fitted with a TOU meter are billed under a non-TOU rate in the meantime). The TOD rate under category 4.1 uses a different set of periods from the TOU rate.

The normal rate for category 3 (category 3.1) and the TOD rate for category 4 (category 4.1) are reserved for existing customers only. New customers therefore fall under the TOU rate (category 3.2 or 4.2). PEA counts a customer as existing if they were already on the old rate before the November 2015 electricity bill. MEA counts a customer as existing if they were on rate 3.1 or 4.1 and had been using electricity before October 2000. Category 5 customers not yet fitted with a TOU meter are billed temporarily under a non-TOU rate.

For the reader, this means all the periods and holidays discussed in this article apply only to TOU rate bills. A TOD rate bill under category 4.1 uses a different set of periods. Before using the Off Peak day calendar to estimate electricity charges, check the customer category and rate type on the bill first, to make sure the right set of periods is being used.