How much CIT does a 500 kW factory save with BOI?

Under CapSolar's baseline model (CAPEX 12.5M, annual profit uplift 2.79M), an 8-yr BOI CIT exemption saves ~THB 4.17M + 0.25M import duty = ~THB 4.4M base. If in an EEC S-curve zone (Rayong/Chonburi/Chachoengsao), add +50% = ~THB 6.5M. See year-by-year in the scenarios table above.

How much does a 2 MW factory save with BOI over 8 years?

A 2 MW factory (CAPEX 54M) saves ~THB 18.4M CIT over 8 years (base) · +9.2M EEC bonus + 1.08M import duty = ~THB 28.7M total. In aggressive scenarios (high TOU peak + 24×7 operation), up to ~THB 41M. See year-by-year 2MW table above.

Is BOI worth applying for a small 100 kW factory?

A 100 kW factory (CAPEX 3.1M) saves ~THB 0.76M over 8 years · BOI filing costs 150-300K · net benefit 4-5× (7-14× with EEC bonus) · worth it if factory has taxable profit. If persistently loss-making or no profit forecast yet, use accelerated depreciation instead — simpler and cheaper.

How many years does BOI shave off payback?

On average BOI shaves 0.8-1.3 yr off payback vs baseline · EEC stacking adds another 0.3-0.4 yr · for 500 kW: baseline 5.0-5.5 yr → with BOI 4.0-4.5 → with BOI+EEC 3.7-4.2 · for 2 MW: 4.6-5.1 → 3.5-4.0. See comparison table in S1.

What happens to the BOI exemption if the factory becomes loss-making?

The exemption can't apply to zero — loss years have no CIT to exempt, so the exemption for that year is forfeited (no carry-forward). Profitable years still get full exemption up to the 8-year cap. If loss-making for 3+ consecutive years, BOI may revoke the promotion certificate (mitigable via annual reports showing external causes like COVID or supply-chain shocks).

BOI + PPA stacking — who gets the tax benefit?

The SPV (owner of the solar asset) receives the BOI exemption. The factory does not file BOI in this structure. However, good SPVs pass that through via lower PPA tariffs — typically 15-30% below grid rate. See PPA framework and EPC vs PPA for structural detail.

BOI · WORKED EXAMPLE · 3 SCENARIOS

BOI Solar Factory Thailand 2026 3 Real Worked Examples

Year-by-year numbers — 100kW saves ~0.76M · 500kW saves ~4.17M · 2MW saves ~18.4M (up to ~28.7M with EEC) over 8 years. Plus 12-month application calendar · PPA/Cash stacking · decision matrix · FAQ.

100 kW · 500 kW · 2 MWYear-by-year · 8 yrEEC +50% · stacking

Run my factory's numbers Ask CapSolar to file BOI

10-min read · 1,800 words · Updated 2026-04-24

Important disclaimer

All numbers are illustrative estimates. Actual BOI benefit depends on your taxable profit, application timing, and Revenue Department rulings. Consult a BOI-approved advisor. Refer to latest announcements at https://www.boi.go.th.

How much THB does BOI Section 7.1 actually save? (3 factory sizes)

BOI solar factory worked example calculation for 3 real scenarios — a 100 kW shop saves ~THB 0.76M in CIT over 8 years · a 500 kW mid-size factory saves ~THB 4.17M · a 2 MW large plant saves ~THB 18.4M base (up to ~THB 28.7M with EEC +50% stacking). This page shows the year-by-year arithmetic, the 12-month application calendar, and when BOI is worth the paperwork — so you can decide before filing.

1. Three real scenarios, side by side

Each card shows inputs (CAPEX, kWh, self-consumption), year-by-year CIT saved, EEC bonus, and a plain-English verdict. CAPEX anchored to CapSolar EPC internal quotes 2026Q1 (3 quotes averaged).

100 kW

Small factory · 100 kW · CapEx ~THB 3.1M

Small food / plastics / packaging SME · roof 500-900 m² · monthly bill 30-80K THB

Inputs (fixed assumptions)

CapEx: ฿3.10M
THB / Wp: 31
Annual kWh: 149K
Self-consumption: 85%
TOU blended rate: 4.50 THB/kWh
Annual savings: ฿570K
Profit uplift (post-O&M): ฿510K
Thai CIT rate: 20%

Year-by-year CIT Savings (8 years)

Year	Taxable uplift	CIT w/o BOI	Saved
Y1	0.51M	102K	102K
Y2	0.51M	101K	101K
Y3	0.50M	100K	100K
Y4	0.49M	98K	98K
Y5	0.48M	96K	96K
Y6	0.47M	94K	94K
Y7	0.46M	92K	92K
Y8	0.45M	90K	90K
Total		฿773K	฿773K

EEC +50% stacking (if eligible)+ ฿387K

Import duty saved (machinery)+ ฿62K

Grand total (BOI + EEC + duty)฿1.22M

Baseline vs BOI

Payback w/o BOI: 5.8-6.3 yr
Payback w/ BOI: 4.8-5.2 yr
Net IRR w/o BOI: 11.2%
Net IRR w/ BOI: 13.5%

Plain-English Verdict

Marginal: BOI filing costs 150-250K THB vs ~763K benefit (4-5× return). If outside EEC and no taxable profit to absorb exemption, use accelerated depreciation instead.

This tier fits you if…

Monthly bill 30-80K THB
Roof < 700 m²
Taxable profit > 500K THB/yr (otherwise BOI has nothing to exempt)
Thai juristic entity (Ltd / Co. Ltd) — not sole proprietorship

Source: CapSolar EPC internal quotes 2026Q1 · BOI Category 7.1 · PEA tariff table 2026-04 · World Bank Global Solar Atlas 2024 (149k kWh/100kW·yr at Central Thailand PVOUT)

500 kW

Mid-size factory · 500 kW · CapEx ~THB 12.5M

Mid-auto / textile / food-beverage factory · roof 3,000-5,000 m² · monthly bill 80-400K THB

Inputs (fixed assumptions)

CapEx: ฿12.50M
THB / Wp: 25
Annual kWh: 745K
Self-consumption: 90%
TOU blended rate: 4.50 THB/kWh
Annual savings: ฿3.02M
Profit uplift (post-O&M): ฿2.79M
Thai CIT rate: 20%

Year-by-year CIT Savings (8 years)

Year	Taxable uplift	CIT w/o BOI	Saved
Y1	2.79M	558K	558K
Y2	2.76M	552K	552K
Y3	2.72M	544K	544K
Y4	2.65M	530K	530K
Y5	2.58M	516K	516K
Y6	2.51M	502K	502K
Y7	2.44M	488K	488K
Y8	2.42M	485K	485K
Total		฿4.17M	฿4.17M

EEC +50% stacking (if eligible)+ ฿2.09M

Import duty saved (machinery)+ ฿250K

Grand total (BOI + EEC + duty)฿6.51M

Baseline vs BOI

Payback w/o BOI: 5.0-5.5 yr
Payback w/ BOI: 4.0-4.5 yr
Net IRR w/o BOI: 14.8%
Net IRR w/ BOI: 17.5%

Plain-English Verdict

Clearly worth it: BOI application costs 200-300K, CIT savings ~4.17M (14× return). EEC location makes it 17×. Shaves ~1.0 yr off payback.

This tier fits you if…

Monthly bill 80-400K THB
Roof 3,000-5,000 m²
2-3 shift operation · self-consumption > 85%
Candidate for multi-phase rollout (expand to 1 MW+ within 3 years)

Source: CapSolar EPC internal quotes 2026Q1 (3 quotes averaged) · BOI Category 7.1 · Thai Revenue Dept CIT 20% guidance · EEC Act B.E. 2561 Section 3

2 MW

Large factory · 2 MW · CapEx ~THB 54M

Large electronics / cold-chain / tier-1 automotive · roof 10,000-18,000 m² · monthly bill > 800K THB

Inputs (fixed assumptions)

CapEx: ฿54.00M
THB / Wp: 27
Annual kWh: 2980K
Self-consumption: 92%
TOU blended rate: 4.50 THB/kWh
Annual savings: ฿12.34M
Profit uplift (post-O&M): ฿11.47M
Thai CIT rate: 20%

Year-by-year CIT Savings (8 years)

Year	Taxable uplift	CIT w/o BOI	Saved
Y1	11.47M	2294K	2294K
Y2	11.65M	2330K	2330K
Y3	11.80M	2360K	2360K
Y4	11.70M	2340K	2340K
Y5	11.52M	2304K	2304K
Y6	11.37M	2274K	2274K
Y7	11.25M	2250K	2250K
Y8	11.24M	2248K	2248K
Total		฿18.40M	฿18.40M

EEC +50% stacking (if eligible)+ ฿9.20M

Import duty saved (machinery)+ ฿1.08M

Grand total (BOI + EEC + duty)฿28.68M

Baseline vs BOI

Payback w/o BOI: 4.6-5.1 yr
Payback w/ BOI: 3.5-4.0 yr
Net IRR w/o BOI: 16.2%
Net IRR w/ BOI: 19.0%

Plain-English Verdict

Must file: CIT savings 18.4M + EEC 9.2M + import duty 1.08M = ~28.7M (BOI cost 400-700K, 40× return). Shaves 1.1-1.3 yr off payback. Also stack Section 30 + optional ESS add-on.

This tier fits you if…

Monthly bill > 800K THB
Roof > 10,000 m² or ground-mount available
24×7 or 3-shift operation · self-consumption > 90%
Considering multi-site / multi-factory BOI portfolio
ESS add-on candidate (peak-shaving + BCM + RE100 if parent requires)

Source: CapSolar EPC internal quotes 2026Q1 · BOI Category 7.1 · BOI processing time statistics 2025 · EEC Act B.E. 2561 Section 3 · MEA tariff table 2026-04

Run my factory's numbers Ask CapSolar to file BOI

YMYL note: Tax outcomes depend on your company's specific facts (profit, sector, EEC status). These numbers are CapSolar engineering estimates cross-checked against public BOI data, not tax advice.

2. When BOI makes sense (and when it doesn't)

7-dimension matrix — self-check before investing in the paperwork. 80%+ of CapSolar customers pass this matrix. For those who don't, we say so directly — we don't sell filings that won't return value.

Factor	BOI makes sense	Marginal	BOI doesn't fit
CAPEX	≥ 8M THB	3-8M THB	< 3M THB
Company structure	Thai juristic entity (Ltd / Public Co)	Branch of foreign Ltd	Sole proprietorship / partnership (not eligible)
Annual taxable profit	> 3M THB (uses full exemption)	0.5-3M THB (partial benefit)	Persistent loss (no CIT to exempt)
Energy use profile	>80% self-consumed during daytime	50-80% self-consumed	<50% self-consumed (export-heavy — different track)
Factory sector	Priority (7.1 renewable / EEC S-curve)	Standard manufacturing	Retail / trading / real estate (not promoted)
Project timeline	Can wait 60-150d	Can wait ≤90d	Must commission within 45d
EEC zone location	Rayong / Chonburi / Chachoengsao + S-curve	In EEC but non-S-curve	Outside EEC

Factory types that typically don't qualify

Pure trading/distribution (no manufacturing uplift for CIT base) · real estate/rental (explicitly excluded from Section 7.1) · food-service/restaurants (service, not manufacturing) · sole-proprietor workshops without Ltd structure (can't receive CIT exemption by entity type) · persistently loss-making operations with no profit forecast (exemption can't apply to zero) · factories commissioning solar within 45 days (not enough time for pre-approval; already-operating systems can retrofit-apply but with reduced benefit). See full legal criteria at BOI Section 7.1 eligibility.

3. Stacking Examples — BOI + Financing Combos

**PPA + BOI** · in a PPA structure, BOI benefits accrue to the SPV (the asset owner), not the factory. Good SPVs pass that through as a 20-30% lower tariff. See what is PPA and EPC vs PPA for framework.

BOI + PPA · 500 kW · EEC (Rayong)

System owner (SPV): CapSolar SPV
Off-taker: Factory (Thai Co.)
CAPEX (SPV side): THB 12.5M
Who files BOI: SPV (asset owner) · not the factory
CIT exemption accrues to: SPV (8 yr, CIT = 0)
Factory CAPEX: 0 THB
Tariff baseline (grid): ~4.50 THB/kWh
PPA tariff after BOI pass-through: 3.40-3.60 THB/kWh (20-24% discount)
Factory savings over 8 yr: ~THB 5.4M (EEC bonus passed through)

BOI + PPA · 2 MW · non-EEC (Ayutthaya)

System owner: CapSolar SPV
CAPEX: THB 54M
Who files BOI: SPV
CIT saved over 8 yr (SPV): THB 18.4M (no EEC bonus)
Tariff baseline: ~4.50 THB/kWh
PPA tariff: 3.30-3.60 THB/kWh (20-27% discount)
Factory savings over 8 yr: THB 22-24M

**Cash Self-Invest + BOI** · factory owns everything, claims exemption directly, no SPV revenue-share. Works when factory has > 12M THB free cash flow and taxable profit to absorb exemption. Below ~3M THB CAPEX, application overhead usually exceeds benefit — use cash + accelerated depreciation instead. See 4-way financing matrix.

BOI + Cash · 500 kW · Bangkok (non-EEC)

CAPEX: THB 12.5M
Who files BOI: Factory itself
CIT exemption: 100% · 8 yr
CIT saved 8 yr: THB 4.17M
EEC bonus: None (Bangkok)
Import duty saved: THB 0.25M
Payback (with BOI): 4.0-4.5 yr
Payback (without BOI): 5.0-5.5 yr

BOI + Cash · 2 MW · Rayong (EEC S-curve)

CAPEX: THB 54M
Who files BOI: Factory itself
CIT exemption (base): 100% · 8 yr
Base CIT saved 8 yr: THB 18.4M
EEC bonus (+50%): + THB 9.2M
Import duty saved: THB 1.08M
Total 8-yr savings: ~THB 28.7M
Payback (BOI + EEC): 3.5-4.0 yr
Payback (without BOI): 4.6-5.1 yr

4. 12-Month BOI Application Calendar

Calendar view — not theoretical steps (parent page covers the 5-step HowTo). This is Jan-Dec of a real filing year with ERC/PEA/MEA parallel tracks overlaid. Key months: Mar (BOI review queue), May (certificate issued), Oct (commissioning).

Month	BOI Action	Parallel ERC / PEA-MEA Action
Month 1	Gather corporate docs (DBD cert, DIW license, 2yr financials)	Energy audit + EPC quote
Month 2	Submit BOI pre-application on portal	ERC pre-consultation (non-binding)
Month 3	BOI officer review (30-45d)	PEA/MEA interconnect study kickoff
Month 4	BOI board meeting slot (if queue permits)	PEA/MEA single-line diagram approved
Month 5	BOI promotion certificate issued	ERC notification form Type 1 filed
Month 6	Accept promotion (6-month acceptance window opens)	ERC acknowledgement (10-30d)
Month 7	Apply for tax ID / investor card	PEA/MEA physical interconnect scheduled
Month 8	Open BOI account at Revenue Department	PV install begins
Month 9	Import solar equipment under 0% duty exemption	Install continues
Month 10	Commissioning + PAC (Provisional Acceptance Certificate)	PEA/MEA net-metering or excess-to-grid config
Month 11	Operational month 1 — file first quarterly CIT with BOI exemption claimed	Monitoring dashboard live
Month 12	Year-end audit prep — segregate BOI-promoted revenue from other revenue	Annual yield report ready

Why steps overlap: parallel tracks save 2-3 months (BOI pre-review runs while PEA interconnect study runs). Common delay points: BOI board queue, PEA interconnect study. If BOI rejects — 30-day appeal window, usually fixable via doc re-submission. Certificate acceptance timing determines which fiscal year the exemption starts in.

5. Calculate for your specific factory

Want a calculator that takes your exact TOU schedule, CAPEX, and EEC eligibility as inputs and produces your custom BOI + payback table? Run our Solar Calculator — it uses the same scenario dataset as this page. Or ask CapSolar to file BOI for you — we file end-to-end from eligibility check through board review.

Solar Calculator

ROI + payback estimator

Subsidy Finder

BOI + EEC + ERC matching

PPA vs Self-Invest

Coming soon

BOI Solar Incentives 2026 — Theory + Eligibility 1 MW Factory Solar Price · 3 BOMs Factory Solar ROI · 3-Shift 24×7 Financing 4-Way · Cash/Loan/Lease/PPA What is a Solar PPA Thailand Factory Electricity Tariff Rayong / EEC · 7-Estate Guide Factory Solar Guide (primer)

Ready to start your factory's BOI application?

Free BOI consultation Solar calculator BOI theory · eligibility

CAPSOLAR HUB · FACTORY SOLAR

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This page is one of 15 topics in the Factory Solar Thailand 2026 master hub — Assess → Design → Finance → Operate.

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Frequently Asked Questions (numeric)

Sources & References

Thailand Board of Investment (BOI, 2026). Investment Promotion Act & Category 7.1 Renewable Energy list.
Eastern Economic Corridor Policy Office (EECO, 2024). EEC Act B.E. 2561 Section 3 — +50% CIT stacking.
Revenue Department Thailand (2026). Corporate Income Tax 20% flat rate + 200% declining-balance depreciation method.
CapSolar EPC internal quotes 2026Q1 (3 quotes averaged per tier, Frank-signed) — CAPEX + THB/Wp baseline.
World Bank Global Solar Atlas 2024 — Central Thailand PVOUT for annual kWh estimates.
PEA tariff table 2026-04 · MEA tariff table 2026-04 — blended TOU 4.50 THB/kWh baseline.

Last fact-check: 2026-04-24 · Next review: 2026-10-24

BOI Solar Factory Thailand 2026 3 Real Worked Examples

How much THB does BOI Section 7.1 actually save? (3 factory sizes)

1. Three real scenarios, side by side

Small factory · 100 kW · CapEx ~THB 3.1M

Inputs (fixed assumptions)

Year-by-year CIT Savings (8 years)

Baseline vs BOI

Plain-English Verdict

This tier fits you if…

Mid-size factory · 500 kW · CapEx ~THB 12.5M

Inputs (fixed assumptions)

Year-by-year CIT Savings (8 years)

Baseline vs BOI

Plain-English Verdict

This tier fits you if…

Large factory · 2 MW · CapEx ~THB 54M

Inputs (fixed assumptions)

Year-by-year CIT Savings (8 years)

Baseline vs BOI

Plain-English Verdict

This tier fits you if…

2. When BOI makes sense (and when it doesn't)

Factory types that typically don't qualify

3. Stacking Examples — BOI + Financing Combos

BOI + PPA · 500 kW · EEC (Rayong)

BOI + PPA · 2 MW · non-EEC (Ayutthaya)

BOI + Cash · 500 kW · Bangkok (non-EEC)

BOI + Cash · 2 MW · Rayong (EEC S-curve)

4. 12-Month BOI Application Calendar

5. Calculate for your specific factory

Solar Calculator

Subsidy Finder

PPA vs Self-Invest

Related articles

Ready to start your factory's BOI application?

Back to the Master Guide

Frequently Asked Questions (numeric)

Sources & References