What's the real payback for a 100 kW factory solar system in Thailand 2026?

Average 4.8-year simple payback assuming THB 3.88/kWh tariff, PVOUT 1,490 kWh/kWp/yr, BOI Section 30 covering 15% of CAPEX, and self-consumption ≥95%. If the factory draws heavily during peak hours (11:00-15:00) where TOU peak rates exceed the average by ~40%, payback drops to 4.3-4.5 years. See the worked table and use /tools/solar-calculator with your real numbers. Returns over the full 25-30 year system life also hinge on panel degradation and lifespan.

How does 1 MW ROI differ from 500 kW?

1 MW beats 500 kW by ~0.9 IRR points (21.7% vs 20.8%) for three reasons: 1) EPC per-watt drops ~10% via economies of scale (THB 23 vs 25/Wp); 2) annual O&M as % of CAPEX falls (1.0% vs 1.3%); 3) in a 3-shift 24/7 factory with baseline load >1 MW, self-consumption hits 100%. Full 1 MW pricing + BOM at /knowledge/solar-panel-price-thailand-2026 (W2 Wed).

Is solar worth it for a factory with only 2 shifts (no night shift)?

Very much so — a 2-shift 08:00-22:00 factory has a load curve that actually aligns better with solar than 3-shift, because peak load tends to sit at 11:00-15:00, matching solar's peak output. Rule of thumb: size solar ≤ 1.2× daytime peak load to keep self-consumption 95%+ and avoid exports that sell at ~40% below tariff. See 100-500 kW worked examples in our 5-size table and the shift-based modeling section.

BOI Section 30 vs 31 — what's the difference and which should I pick?

Section 30 = 5-8 year corporate tax holiday (by project class). Section 31 = 8-year tax holiday + 7% import-VAT exemption + deductions for transport and utility costs. SME factories with <THB 10M CAPEX usually take Section 30 (simpler/faster). 1 MW+ projects (THB 25M+) prefer Section 31 — the VAT + transport deductions save more. Consult CapSolar — we've handled 100+ BOI applications. Full detail at /knowledge/boi-solar-incentives-2026.

How does PPA ROI differ from EPC — which should I pick?

EPC = you invest CAPEX, earn 21-23% IRR over 25 years, own the asset. PPA = zero CAPEX, buy power from CapSolar at THB 3.30-3.50/kWh (10-15% below tariff), no ownership but zero maintenance risk. CFOs pick EPC when they have low WACC + cash reserves + want to maximize long-term ROI. CFOs pick PPA for zero-CAPEX + conservative balance sheet + or leased rooftop. Full 12-dimension comparison at /knowledge/ppa-vs-epc.

What's the LCOE of solar in Thailand 2026 vs grid tariff?

Factory solar LCOE 2026: THB 1.20-1.32/kWh for 100kW-5MW (post-BOI). Grid industrial TOU average: THB 3.88-3.95/kWh. Solar is ~3× cheaper — meaning solar pays back at any factory with >50% daytime load. Even in the downside — tariff drops 30% (ERC revision) and escalation = 0% — solar LCOE still halves grid cost. Full math in the 5-size table. To find your own daytime-load share, start with a factory energy audit. If you're adding storage, check the BESS price 2026 (฿/kWh) & when it pays back.

When is solar NOT worth it for a factory?

Solar is usually "not yet" worth it when a factory runs mostly on night shifts (low self-consumption because solar generates by day), has a leased roof with under 5 years remaining, has a structurally weak roof needing heavy reinforcement, has a very low monthly bill, plans an imminent relocation or closure, or would export more than ~40% of energy to the grid at a low feed-in rate. If these apply, fix the condition first — or consider a zero-CAPEX PPA instead of self-investing. See the full decision checklist.

Investment Guide — 2026

Factory Solar ROI — How Fast Is Payback? Calculate ROI for 5 Sizes · 4.0-4.8 Year Payback (2026)

Model your factory solar return seriously — payback, IRR, NPV, LCOE across 5 real sizes (100kW, 500kW, 1MW, 2MW, 5MW), shift-based load profiles competitors never cover, BOI tax-holiday impact, and real Thai bank green-loan rates.

ERC 2026 · THB 3.88-3.95/kWhPVOUT 1,490 kWh/kWp/yrBOI 8-yr tax holiday

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14-min read

How Factory Solar ROI Differs from Residential

Thailand factory solar ROI in 2026 averages 4.0-4.8-year payback — much faster than residential (6-8 years) because factories consume ~100% of generation during daylight (high self-consumption), don't depend on net metering, qualify for 8-year BOI tax holidays (unavailable to residential), and benefit from economies of scale (EPC per-watt drops 15-20% at 1 MW+). Key variables that swing ROI: shift profile (load curve), BOI section tier, existing roof structural cost, tariff escalation rate.

3 ROI Mistakes Factory CFOs Routinely Make

1) Computing "electricity cost saved" from flat average tariff — ignoring that daytime-running factories pay peak-hour rates ~40% higher than off-peak. Solar displaces peak directly, so ROI is 15-20% higher than a flat-rate model suggests. 2) Forgetting tariff escalation — ERC has raised tariffs 3-4% annually for the past decade, but CFOs often lock in the investment-year rate, under-estimating 25-year NPV by ~25%. 3) Missing BOI Section 30/31 — the 8-year tax holiday + VAT exemption drops effective CAPEX from THB 22-26/Wp to THB 18-22/Wp, cutting payback by an average 1.5 years. This guide corrects all three with real numbers.

The 7 Variables of Factory Solar ROI

Accurate solar ROI requires plugging all 7 variables below into a 25-year cash-flow model (not a single-year simple payback). The seven are: CapEx, OpEx, tariff structure, tariff escalation, discount rate, degradation, O&M & insurance.

1. CAPEX (Upfront Investment)

THB 22-26/Wp installed (2026) for 100kW-500kW, THB 21.5-23/Wp for 1MW+. Covers panels, inverter, BOS, labor, commissioning. Excludes new roof structural work. BOI reduces this by ~15% (details at /knowledge/boi-solar-incentives-2026).

2. Tariff Savings (revenue)

ERC 2026: THB 3.88-3.95/kWh average (industrial TOU Cat 3-4) × PVOUT 1,490 kWh/kWp × installed kW = first-year savings. Warning: don't use a flat tariff if the factory runs during peak — use actual peak rate.

3. Tariff Escalation Rate

ERC 10-year historical: ~3.2%/yr. Use 3% in base case, 4% aggressive, 2% conservative — the spread shifts NPV by ~35%.

4. Degradation Rate

Tier-1 mono panel: year-1 drop 2.5%, then 0.5%/yr. 25-year warranty: >83% of original rated power. Model must use this curve, not flat.

5. O&M + Insurance

THB 150-200k/MW/year — covers 4x cleaning, inspections, remote monitoring, all-risk insurance. About 1-1.5% of CAPEX annually; an OpEx line many CFOs forget.

6. Discount Rate (WACC)

Use factory's WACC (typically 7-10% for Thai SME, 5-8% for BOI-backed corporates). Lower WACC → higher NPV → more attractive investment.

7. BOI Tax Impact

Sections 30/31 grant an 8-year corporate tax holiday + 7% import VAT exemption. Net impact: 2-3 percentage points higher 25-year ROI. See /knowledge/boi-solar-incentives-2026.

Grid export income: Thailand Net Metering 2026 policy

5 Real Factory Sizes — Worked Payback / IRR / NPV

We model 5 sizes common in Thai industry — 100 kW (SME), 500 kW (mid-market), 1 MW (mainstream), 2 MW (major), 5 MW (utility-scale). All numbers use ERC 2026 tariff, PVOUT 1,490, WACC 8%, tariff escalation 3%/yr, BOI Section 30 (8-year tax holiday). This table is the golden benchmark.

Size	CAPEX (after BOI)	Year-1 savings	Payback	25-yr IRR	25-yr NPV (@ 8%)	LCOE
100 kW	฿2.04M	฿580K	4.8 yr	19.2%	฿4.10M	1.32THB/kWh
500 kW	฿9.78M	฿2.90M	4.5 yr	20.8%	฿22.00M	1.28THB/kWh
1 MW	฿19.55M	฿5.82M	4.3 yr	21.7%	฿46.50M	1.24THB/kWh
2 MW	฿37.40M	฿11.45M	4.1 yr	22.4%	฿98.00M	1.22THB/kWh
5 MW	฿91.38M	฿28.70M	4.0 yr	22.9%	฿250.00M	1.20THB/kWh

Electronics plant · petrochemical (phase 1) · large warehouse

1 MW

Simple payback

4.3 years

Roof area: 6,800 sqm
Annual generation: 1,490,000 kWh/yr
CAPEX (after BOI): ฿19.55M
25-year IRR: 21.7%
25-year NPV (@ 8%): ฿46.50M
LCOE: 1.24 THB/kWh
Shift profile (illustrative): Continuous 3-shift 24h · daytime load 1,100 kW fully absorbs generation peak
Analysis: 1 MW is a key threshold — EPC price-per-watt drops ~10% vs 500 kW due to economies of scale. 3-shift factories consuming 250,000+ kWh/month absorb all generation during daylight — no grid export needed, maximizing IRR (21.7% over 25 years). Full price BOM at /knowledge/solar-panel-price-thailand-2026.

Avoids 619 tons CO₂/yr · 15,475 tons over 25 years · solar carbon calculator Thailand

Shift-Based ROI Adjustments — 24/7 vs 3-shift vs 2-shift (What Competitors Miss)

Competitors like GreenYellow and Thai Solar Energy model ROI assuming a factory absorbs 100% of solar generation — which isn't true. A factory's load curve dictates its self-consumption rate, and self-consumption rate drives real ROI. Three profiles we see in the field:

24/7

A) Continuous 24/7 (cold-storage, semiconductor, data center, petrochemical)

Baseline load 4-10 MW around the clock · 1-5 MW solar is absorbed at 100% instantly · self-consumption = 100% · zero curtailment, no net-metering dependency · highest IRR (22-23%). ROI is 15-20% above what competitors quote because there's no grid-export discount to model.

3-shift

B) 3-shift 24h weekdays (electronics, auto-parts 3-shift, large textile)

3-shift Mon-Fri, weekend load drops 30-50% · Sunday afternoon solar can exceed peak load → ~3-5% export · self-consumption 95-97%. ROI remains high but the model must correctly discount exports (PEA buys excess at ~THB 2.2/kWh, below tariff).

2-shift

C) 2-shift 08:00-22:00 (food-processing, SME, fab shop)

Daytime load aligns well with solar profile, but tail hours 16:00-18:00 see solar drop ≤60%. Peak-hour load (11:00-15:00) at high TOU rates is fully displaced — maximum benefit. ROI optimal at 100-500 kW where solar doesn't exceed daytime baseline. Rule of thumb: size solar ≤1.2× of daytime peak load to keep self-consumption >95%.

Takeaway: size solar to shift profile, not maximum roof area. Self-consumption rate 95%+ is the ROI sweet spot. If roof exceeds load capacity, consider partial PPA export or reserve area for a phase-2 expansion.

Calculate Your Factory's ROI — 5 Minutes

The examples above use industry averages — yours may differ (actual TOU peak rate, real load curve, roof tilt/orientation affecting PVOUT). Use /tools/solar-calculator with 5 inputs (monthly kWh, average tariff, roof area, province, usage type) to get your 25-year ROI in under 30 seconds. Or book a full site assessment (free). Before running the numbers, learn how to size a factory solar system and how many kWp your plant needs. To see where every baht goes, read our full solar installation cost breakdown (per-kW, 2026), or review the real returns from our automotive-plant solar project in Ayutthaya. And account for the monsoon — see solar output in Thailand's rainy season.

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3 Financing Options — Cash / Loan / PPA

ROI shifts with financing structure. CFOs should benchmark 3 models:

Option	Rate / Cost	Payback	IRR	Best for
Cash	0% (own cost of capital)	4.0-4.8 yr	21-23% 25-yr	Best for: companies with cash reserves + low WACC + wanting asset ownership
Green Loan (Krungsri/EXIM/KBank)	5.5-7% APR · 7-10-yr term	net-positive cash flow year 1-2	16-19% 25-yr (equity)	Best for: SME / mid-market with credit wanting to preserve cash for expansion
PPA (power purchase)	0 CAPEX · THB 3.30-3.50/kWh × 15-20 yr	immediate savings	N/A (non-owner) · 10-15% below tariff	Best for: zero-CAPEX preference, cash-conservative, or leased rooftop

Full comparators: PPA vs EPC compared (2-way), /knowledge/solar-epc-vs-rental-thailand (3-way + TFRS 16), /knowledge/solar-financing-thailand-factory (4-way Cash/Loan/Lease/PPA with Thai bank rates + 25-yr NPV). If your roof is too small, you can still procure clean power off-site via renewable energy wheeling (TPA) in Thailand.

BOI Section 30/31 — Cuts Payback by 1.5 Years on Average

Thailand Board of Investment (BOI) is the government agency granting tax privileges for renewable-energy projects. Section 30 provides 5-8 year tax holidays; Section 31 grants 8-year corporate income tax exemption + 7% VAT exemption on equipment imports. ROI impact: 1) CAPEX drops ~15% on average (THB 22-26/Wp → THB 18-22/Wp); 2) the 8-year tax holiday lifts after-tax cash flow ~20% during the payback window; 3) combined, average payback falls from 5.5-6 years → 4.0-4.5 years, and 25-year IRR rises from 18-19% → 21-23%. Requirements: BOI application (2-4 months), minimum investment THB 1M, and at least 30% local content (labor + installation). Full details at /knowledge/boi-solar-incentives-2026 (W3 Tue). If you choose a PPA, review the PPA clauses that affect your ROI, such as the escalator and buyout terms.

4 Risks to Model Explicitly

1) Grid interconnection with PEA/MEA: >1 MW requires transformer capacity review (6-9 month buffer). 2) PEA quota: some provinces have quotas (parts of EEC) — wait-list risk. 3) Tariff cap risk: ERC may revise feed-in tariff (policy under review). 4) Roof asset risk: roofs with <10-year remaining life may need replacement, adding 10-15% to CAPEX. Include sensitivity analysis for all 4 in base/upside/downside cases.

How to Calculate Your Factory Solar ROI — 5 Steps

Use these steps in-house with your finance team, alongside /tools/solar-calculator.

1
1) Pull 12-month electricity bills
Request 12 months of PEA/MEA bills. Record monthly kWh, TOU peak/off-peak rates, demand charge, Ft — establishing baseline.
2
2) Measure daytime load
Install a smart meter or request interval data from PEA. Review the 09:00-17:00 load curve. Size solar ≤ daytime peak × 1.2.
3
3) Get 3 EPC quotes
Request quotes from BOI-certified EPCs with 100+ installations + trilingual team. Compare THB/Wp, warranty, timeline. Recommended shortlist at /knowledge/thai-factory-solar-vendors. Use our 20-point procurement checklist to verify every critical point.
4
4) Build 25-year cash flow model
Excel or use /tools/solar-calculator. Plug in the 7 variables (CAPEX, savings, escalation, degradation, O&M, discount, BOI). Compute payback, IRR, NPV.
5
5) Run sensitivity analysis
Create base/upside/downside cases — flex tariff escalation ±1%, CAPEX ±10%, degradation ±0.5%/yr. Obtain an IRR/payback range. CFO should see the range before signing.

Industry-Specific Solar ROI

Solar ROI varies by load profile, demand charges, and operating hours — see the ROI analysis for your industry

Want real ROI figures from factories that already went solar? See our real factory solar case studies with measured savings and payback before you decide.

Hospital & Healthcare

24-hour load = high self-consumption → faster payback

University & School

Large rooftops + ฿2-5M/yr bills → IRR 15-22%

Shopping Mall & Retail

AC peak matches solar peak → above-average ROI

Cement & Concrete

Highest industrial demand → high NPV even with longer payback

Sugar Mill & Ethanol

Off-season = 100% self-consumption → fast payback

Mining & Quarry

Replace diesel genset 40-60% → IRR 18-25%

Rice Mill

Milling + drying in daytime → better ROI than 3-shift

Port & Logistics Hub

Warehouse roofs 10,000+ sqm → large system = lower cost/Watt

Airport & Transport Hub

Massive area + 24/7 load → highest NPV in category

EV Battery Manufacturing

BOI Super Cluster + RE100 requirement → IRR 20%+

CAPSOLAR HUB · FACTORY SOLAR

Back to the Master Guide

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

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Is Factory Solar Worth It? — A Decision Checklist

Before crunching detailed numbers, match your factory against the two columns below. If you mostly fall on the "worth it" side, payback is typically in the 4-6 year range and it's worth running a real ROI. If several "not yet" conditions apply, fix those first — or consider a PPA instead of self-investment.

Worth it — when your factory meets these

: Daytime-dominant load (daytime / 2-3 shifts) that aligns with solar generation
: Monthly electricity bill of roughly 50,000 THB or more
: Usable roof area of roughly 500 m² or more
: Self-consumption of ~70% or higher (you use most generation on-site, little export)
: Plan to occupy the building / site for at least 8 years
: TOU on-peak hours overlap with the midday solar generation window

Not yet — when these conditions still apply

: Mostly night-shift load — solar generates by day, so self-consumption is low
: Leased roof with less than 5 years remaining on the lease
: Structurally weak roof needing heavy reinforcement before installation
: Very low monthly bill (savings won't justify install cost)
: Imminent relocation or site closure planned
: More than ~40% of energy exported to the grid at a low feed-in rate

Mostly on the "worth it" side? Calculate your real payback / IRR / NPV below.

Frequently Asked Questions

Written by Frank Lee · Founder, CapSolar

Frank Lee is the founder of CapSolar, a BOI-certified solar EPC firm (founded 2023) serving factories across Thailand. Frank manages a 80+ MWp portfolio across 150+ commercial projects in Bangkok / EEC / northern provinces. This guide was reviewed by CapSolar's Chief Engineer for engineering and financial accuracy.

Published 2026-04-23 · Last updated 2026-04-23

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Factory Solar ROI — How Fast Is Payback? Calculate ROI for 5 Sizes · 4.0-4.8 Year Payback (2026)

How Factory Solar ROI Differs from Residential

3 ROI Mistakes Factory CFOs Routinely Make

The 7 Variables of Factory Solar ROI

1. CAPEX (Upfront Investment)

2. Tariff Savings (revenue)

3. Tariff Escalation Rate

4. Degradation Rate

5. O&M + Insurance

6. Discount Rate (WACC)

7. BOI Tax Impact

5 Real Factory Sizes — Worked Payback / IRR / NPV

1 MW

Shift-Based ROI Adjustments — 24/7 vs 3-shift vs 2-shift (What Competitors Miss)

A) Continuous 24/7 (cold-storage, semiconductor, data center, petrochemical)

B) 3-shift 24h weekdays (electronics, auto-parts 3-shift, large textile)

C) 2-shift 08:00-22:00 (food-processing, SME, fab shop)

Calculate Your Factory's ROI — 5 Minutes

3 Financing Options — Cash / Loan / PPA

BOI Section 30/31 — Cuts Payback by 1.5 Years on Average

4 Risks to Model Explicitly

How to Calculate Your Factory Solar ROI — 5 Steps

1) Pull 12-month electricity bills

2) Measure daytime load

3) Get 3 EPC quotes

4) Build 25-year cash flow model

5) Run sensitivity analysis

Industry-Specific Solar ROI

Back to the Master Guide

Is Factory Solar Worth It? — A Decision Checklist

Worth it — when your factory meets these

Not yet — when these conditions still apply

Frequently Asked Questions

Written by Frank Lee · Founder, CapSolar

Ready for Your Factory's Real ROI?

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Solar ROI by Industry

Dental Clinic

Dry Cleaning & Commercial Laundry

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Solar Panel Recycling & Disposal

Telecom Tower & Base Station

Theme Park & Amusement

University & School

Veterinary & Animal Hospital

Wedding & Banquet Hall

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