May–Aug 2026 — first edition
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).
Data Index · Updated Every Ft Period
Thailand Factory Electricity Cost Index
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.
8 min readLast updated: May–Aug 2026 period (first edition)Data as of: May–Aug 2026
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.
The Index: All-In Factory Electricity Price, May–Aug 2026 (THB/kWh)
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.
Ft Trend, Last 6 Periods (the Index's Main Mover)
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 | Pending (expected late Aug) |
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.
As a Monthly / Annual Bill for the Prototype Factories
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).
Methodology (Every Assumption Published)
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 kWh- Energy rates (ex-Ft/VAT): Type 3 TOU 12–24 kV = On-Peak 4.1839 / Off-Peak 2.6037 THB/kWh; Type 4 TOU ≥69 kV = 4.1025 / 2.5849, per the MEA/PEA schedules (ERC-set national rates).
- Demand rates: 132.93 THB/kW (TOU 12–24 kV) and 74.14 THB/kW (TOU ≥69 kV); Type 3–4 service charge = 312.24 THB/month.
- Current-period Ft (May–Aug 2026) = 0.1623 THB/kWh per the ERC announcement — each new period, the index is recomputed on that period's Ft.
- Load profile: 65% On-Peak / 35% Off-Peak units (a daytime-running factory — the same split as this site's standard worked examples). Monthly energy: 100 kW → 30,000 kWh (≈ one shift), 500 kW → 150,000 kWh, 1 MW → 400,000 kWh (≈ two shifts).
- Billed demand = exactly the prototype's rated kW (100 / 500 / 1,000 kW) — a real factory that manages its peak well will land slightly below the model.
- Excluded: power-factor penalties (assumed corrected), customer-specific discounts/penalties, and temporary government relief measures.
- Type 3 also has a normal-rate option (demand + single energy rate) and Type 4 a legacy TOD schedule — the index benchmarks on TOU because that is what most factories are actually on today (new Type 4 connections default to TOU). Structure details in the Demand Charge / TOU / TOD guide.
Citation 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.
Per-Period Changelog
The index is updated every Ft period (3 per year). Each period gets a permanent anchor (#period-year-period) for stable external citation:
Next period, Sep–Dec 2026: the ERC has not yet announced the Ft (expected late August) — the index will be recomputed and a #period-2569-3 entry added as soon as it lands.
Who Maintains This Index
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.
FAQ
For May–Aug 2026, per this index: a 100 kW factory ≈ 4.25 THB/kWh, 500 kW ≈ 4.24, and 1 MW (Type 4 TOU, ≥69 kV) ≈ 3.92 THB/kWh — including TOU energy + demand charge + service charge + Ft (before 7% VAT). The larger the factory and the higher the voltage, the lower the per-kWh price.
Related Reading
Factory Electricity Cost (Explainer)
Cat 3/4/5 structure, worked examples, PF penalties
TCSPI — Solar Payback Index
The sister index, return side: payback across 12 industries
Ft History Table 2020–2026
Every Ft period since 2020, with why it moved
Calculate Your Factory Bill in 5 Steps
Plug in your own bill numbers
Demand Charge / TOU / TOD
How the demand charge works and where to cut it
Thailand Electricity Tariff 2026 (all types)
Full rate card for every customer type + current Ft
Is Your Factory Paying Above the Index?
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.