3-Phase Electricity Cost in Thailand 2026 — and how the application cost differs from single-phase
This question rests on a premise that is not true, and correcting the premise is the answer. Thailand does not price electricity by phase count: the per-unit rate is set by customer class and by how many units you use in a month. This page gives the real figure a three-phase home pays, sets out exactly what does and does not differ from single-phase, and states the one-off application fee.
There is no three-phase tariff, and there never was one. A Thai per-unit rate is set by exactly two things: your customer class (residential, general business, industrial, agricultural) and the number of units you use that month. Phase count is not in the equation. A home with a three-phase meter sits above the "not exceeding 5 A, 220 V, single-phase" threshold that defines Type 1.1, so it is billed as Type 1.2 — the same progressive ladder as any single-phase household above 150 units. At 200 units that works out to about 4.04 THB/unit, at 300 units about 4.26, at 500 units about 4.47, once the 0.1623 THB Ft, the 24.62 THB service charge and 7% VAT are included — the identical figure a single-phase home on the same consumption pays, to the baht. What three phases genuinely changes is the one-off application fee, the meter and main breaker, and how much load the supply can carry. Full rate ladder: how many baht per unit 2026. Application process: applying for a meter, cost and steps.
Why phase count has no effect on the per-unit price
The Thai tariff structure divides customers by how the supply is used, not by the electrical shape of the wires entering the building. Three points cover it.
Your class comes from how you use power
Residential, general business, industrial, agricultural pumping — the test is what the supply is for, not how many conductors arrive. A house is a residential customer whether it is fed by one phase or three.
The ladder comes from monthly units
Inside the residential class the split is whether you use more than 150 units a month. Type 1.1 carries a 8.19 THB monthly service charge, Type 1.2 carries 24.62 THB. Almost every three-phase home is in 1.2, because the reason for going three-phase in the first place is heavy use.
Phases set capacity, not price
A three-phase supply spreads load across three conductors, so it can deliver more power at the same current per conductor. That suits a house with several air-conditioners, a high-power water heater, a large pump or an EV charger. All of that is a capability question, not a tariff question.
So what does change the rate? Changing customer class (registering as a business, say), or moving to a TOU meter that prices by time of day. Both are independent of phase count and both are available on single-phase and three-phase alike. TOU criteria: is a TOU meter worth it.
What a three-phase home actually pays, per unit and per bill
The table is computed from the actual residential tariff (progressive tiers + Ft 0.1623 + service charge + 7% VAT) at consumption levels typical of a three-phase home. To be explicit: every cell applies equally to a single-phase home on the same consumption. This table answers "how much per unit for 3-phase" precisely because the figure is not specific to three-phase at all.
| Monthly use | Effective cost/unit (all-in) | Class |
|---|---|---|
| 150 units | 3.93 THB | 1.1 |
| 200 units | 4.04 THB | 1.2 |
| 300 units | 4.26 THB | 1.2 |
| 500 units | 4.47 THB | 1.2 |
Read the table correctly: the middle column is not a fixed unit price but the whole bill divided by units, so it rises with consumption because the tariff is progressive — 300 units costs about 1277 THB in total, 500 units about 2237 THB. The 3.95 THB/unit figure quoted in the news is the average of the entire power system, not any one household's rate. For your own number, enter your monthly units in the electricity bill calculator.
Single-phase versus three-phase: what actually differs
These four rows are everything that differs and everything that does not, ordered by how often it is asked.
| Item | Single-phase | Three-phase |
|---|---|---|
| Price per unit | Residential progressive ladder | Exactly the same |
| Monthly service charge | 8.19 or 24.62 THB by class | 24.62 THB (almost all are Type 1.2) |
| MEA inspection fee on application | 700 THB | 1,500 THB, or 2,500 THB for the larger sizes |
| Load the supply can carry | Enough for an ordinary house | Carries a higher total load at the same current per conductor |
Those fees are MEA's, verified as of June 2026: single-phase 5(15), 15(45) and 30(100) sizes are 700 THB; three-phase 30(100) and 50(150) are 1,500 THB; the 200 and 400 sizes are 2,500 THB. New residential applicants to MEA pay no security deposit. PEA fees in the provinces vary by size and area — confirm on 1129 before filing. Documents and full process: applying for a meter, cost and steps.
If it is not a home but a shop or a business
Many people searching "3-phase supply, price" are opening a shop, building a cold room or installing small machinery. That case is different — registering as a business moves you out of the residential class into general business, which sits in the region of 4.18 THB/unit, is not tiered the way a household is, and can carry a separate demand charge once the load grows. Note that the variable moving the price is the customer class, not the phase count, again. If the load reaches factory scale the bill structure changes shape again: how a factory electricity bill works.
So which homes should go three-phase
Because the per-unit price does not differ, the question is not whether it pays off but whether you need it. These four are the common signals.
The main breaker trips when several loads run together. Air-conditioners plus a water heater tripping the main is a capacity limit on the meter and main, not a billing problem.
You are installing a wall-mounted EV charger. Higher-power home chargers usually want a circuit beyond what the existing meter supports; have the utility assess total load before you buy the unit.
A piece of equipment specifies a three-phase supply. Large pumps, home lifts and some machinery are designed for three-phase directly; in that case there is no alternative.
You are building a large house. Asking for three phases at the first meter application is cheaper and simpler than converting later, because a conversion carries both a fee and rewiring. Let the utility size it from your load schedule rather than guessing.
One thing to be clear about before deciding: going three-phase does not make electricity cheaper, and it does not make it dearer either. It changes the capability of the supply and the one-off installation cost, nothing else. If the goal is a smaller bill, the variables that actually move are the units you use and — on a TOU meter — when you use them. Starting point: why your electricity bill is high.
Who wrote this
Frank Lee, Founder of CapSolar — a commercial solar design-and-build company in Thailand with 80+ MWp installed across 150+ projects, 100+ clients served and 85K+ tons of CO₂ avoided. Reading single-line diagrams, meter sizes and real bill structures is daily work here, so this page explains from the tariff structure itself rather than from news summaries.
FAQ
Going three-phase because the load grew? Rooftop solar cuts the daytime load
Air-conditioning, pumps and refrigeration peak at exactly the hours the sun is strongest. CapSolar will assess for free how much of that load your roof could take.