May–Aug 2026: a 1 MW factory (Type 4 TOU, ≥69 kV) pays an ALL-IN average of 3.92 THB/kWh (≈ 4.19 incl. VAT). Full benchmark for 100 kW / 500 kW / 1 MW with every assumption published.
The CapSolar Thailand Factory Electricity Cost Index for May–Aug 2026: the ALL-IN electricity price — TOU energy + demand charge + service charge + the Ft of 0.1623 THB/kWh — works out to 4.25 THB/kWh for a 100 kW factory, 4.24 for 500 kW, and 3.92 for a 1 MW factory (Type 4 TOU, ≥69 kV), all before 7% VAT. The figures are pure arithmetic on the official ERC/MEA/PEA schedules (not a bill survey) and are refreshed every Ft period. Thailand's 3.95 THB/kWh national retail average is a different number from this index, because the index folds the factory demand charge in. The full formula and assumptions are published in the methodology section below.
Published utility rates are only the per-kWh "sticker price" — a real factory bill adds a demand charge (billed on peak kW), a monthly service charge, and the Ft. This table folds every component in and divides back out to the per-kWh price a prototype factory actually pays across the whole bill, at three sizes. MEA (Bangkok/Nonthaburi/Samut Prakan) and PEA (the other 74 provinces) use the same national energy schedule set by the ERC, so the figures apply under either utility.
| Customer type / voltage | Prototype | kWh/month | All-in (before VAT) | Incl. 7% VAT |
|---|---|---|---|---|
| Type 2 small business (<30 kW, flat) | Small workshop | — | ≈ 4.18 | ≈ 4.47 |
| Type 3 medium TOU (12–24 kV) | 100 kW | 30,000 | 4.25 | 4.54 |
| Type 3 medium TOU (12–24 kV) | 500 kW | 150,000 | 4.24 | 4.53 |
| Type 4 large TOU (12–24 kV) | 1 MW | 400,000 | 4.13 | 4.42 |
| Type 4 large TOU (≥69 kV) | 1 MW | 400,000 | 3.92 | 4.19 |
Note: the Type 2 row is a flat-rate reference (no demand charge) of about 4.18 THB/kWh incl. Ft, per the Thailand electricity tariff page. The remaining rows are computed from the prototype model (65% On-Peak / 35% Off-Peak, billed demand = rated kW, 312.24 THB/month service charge, Ft 0.1623) — full assumptions in the methodology section.
The MEA/PEA base energy rates barely move between periods — what moves the index each period is the Ft, announced by the ERC every 4 months (3 periods a year: Jan–Apr / May–Aug / Sep–Dec). The current May–Aug 2026 period sits at 0.1623 THB/kWh.
| Period | Ft (THB/kWh) |
|---|---|
| Jan–Apr 2025 | 0.3672 |
| May–Aug 2025 | 0.1972 |
| Sep–Dec 2025 | 0.1572 |
| Jan–Apr 2026 | 0.0972 |
| May–Aug 2026 (current) | 0.1623 |
| Sep–Dec 2026 | 0.1623 (announced 22 Jul — frozen, effective 1 Sep) |
See the complete per-period Ft table back to 2020 on the Ft history timeline, and what the Ft actually is on the Ft explainer.
The same index figures, converted into prototype-factory bill totals (before VAT), to show the scale of energy cost a finance team is planning around:
| Prototype | Bill/month (THB) | Cost/year (M THB) |
|---|---|---|
| 100 kW (Type 3 TOU, 12–24 kV) | 127,399 | 1.53 |
| 500 kW (Type 3 TOU, 12–24 kV) | 635,747 | 7.63 |
| 1 MW (Type 4 TOU, ≥69 kV) | 1,567,908 | 18.81 |
To split your own bill into energy / demand / Ft, run it through the free bill analyzer or follow the 5-step factory bill calculation guide. For the investment-return side, see this page's sister index: TCSPI — the Thailand solar payback index by industry (cost index = input side, TCSPI = return side).
This index is a RATE MODEL — pure arithmetic on the tariff schedules MEA/PEA publish under ERC resolutions, not a survey of any factory's actual bills. The per-prototype monthly formula is:
All-in THB/kWh = [ (On-Peak kWh × On-Peak rate) + (Off-Peak kWh × Off-Peak rate) + (kW × demand rate) + 312.24 service charge + (total kWh × Ft) ] ÷ total kWhCitation note: index figures are "model prototype all-in averages," not official utility rates and not the 3.95 THB/kWh national retail average. When citing, please attribute as "CapSolar Factory Electricity Cost Index, May–Aug 2026" with a link back to this page.
The index is updated every Ft period (3 per year). Each period gets a permanent anchor (#period-year-period) for stable external citation:
The ERC resolved to freeze the Sep–Dec 2026 Ft at 0.1623 THB/kWh, same as May–Aug (funded by ~16,127M THB of Claw-back money) — so the index values for every factory size carry over unchanged, effective 1 Sep – 31 Dec 2026.
First publication, on current-period data: Ft 0.1623 THB/kWh → 1 MW index (Type 4 TOU ≥69 kV) = 3.92 THB/kWh, 500 kW = 4.24, 100 kW = 4.25 (before VAT).
Next period, Jan–Apr 2027: the ERC is expected to announce the Ft around late December 2026 — the index will be recomputed and a #period-2570-1 entry added as soon as it lands.
This index is prepared and refreshed every Ft period by Frank Lee, Founder of CapSolar, a commercial & industrial solar provider with 80+ MWp delivered across 150+ projects for 100+ clients. The team works with real factory electricity bills daily and sanity-checks each edition against actual bill structures before publishing.
Cat 3/4/5 structure, worked examples, PF penalties
The sister index, return side: payback across 12 industries
Every Ft period since 2020, with why it moved
Plug in your own bill numbers
How the demand charge works and where to cut it
Full rate card for every customer type + current Ft
Send CapSolar your bill for a free analysis — benchmarked against the index, demand/Ft split out, and a concrete estimate of what solar cuts per kWh.