What is the difference between EPC and PPA?

EPC means you invest in and own the entire solar system, getting free electricity after payback (4-7 years). PPA means the provider invests and owns the system — you pay monthly electricity at a discounted rate (10-30% savings) for the 15-25 year contract. EPC has higher ROI but requires capital; PPA needs no investment but saves less.

How much does a 1 MW system cost?

A 1 MW system costs approximately 25-35M THB (22-26 THB/Wp) depending on panel tier, inverter quality, and installation complexity. Tier-1 Premium costs more but delivers better performance and warranty. BOI incentives reduce the net cost by 15-25%.

What is the EPC payback period?

On average, 4-7 years depending on system size, electricity rate, sunshine hours, and BOI benefits. Factories with high daytime consumption (high self-consumption) pay back faster. BOI incentives can reduce payback by 1-2 years.

What permits are required for solar EPC?

Three main groups: (1) ERC notification for systems up to 1 MW (2) PEA or MEA interconnection approval (3) Local building modification permit (อ.6). For systems > 1 MW, a power generation license is needed. CapSolar handles all documentation for clients.

How long does a solar EPC system last?

Solar panels last 25-30+ years with only 0.5%/year degradation (87.5% output after 25 years). Inverters last 10-15 years and may need 1-2 replacements over the system lifetime. Cables and mounting systems last the full panel lifespan.

How to apply for BOI solar incentives?

Apply for a BOI promotion certificate under Activity 5.4: (1) Prepare documents — investment plan, factory license (2) Submit online via e-Investment (3) BOI reviews in 30-60 days (4) Receive promotion certificate. CapSolar helps prepare and submit for clients.

Which solar panel brand should I choose?

Choose Tier-1 brands listed on the Bloomberg BNEF Tier-1 list such as Longi, JA Solar, Trina, Canadian Solar, or Jinko. Tier-1 panels have long warranties, consistent performance, and Thai-based after-sales service. For inverters, consider Huawei, Sungrow, or SMA.

Does the system work on cloudy/rainy days?

It works but produces less. Cloudy days yield 20-40% of sunny day output, heavy rain may drop to 10-20%. Our ROI calculations use year-round averages (including 4-5 months of rainy season) so the figures reflect reality, not just sunny-day projections.

Can a factory on rented land install solar EPC?

Yes, but you need the building owner's permission and a long enough lease to justify the investment (at least 10 years). If your lease is shorter than 7 years, PPA may be a better choice since no investment is required.

What does CapSolar's EPC service cover?

CapSolar provides full-cycle EPC: site survey, system design, Tier-1 equipment procurement, installation, PEA/MEA/BOI permit handling, testing, handover, and lifetime O&M. Licensed electrical engineers, 16.5 MWp across 8 projects in Thailand, trilingual support (TH/EN/ZH).

Pillar Guide

Solar EPC Thailand Factory Guide 2026

Name: CapSolar
Address: 429/44 Sukhonthasawat Rd, Lat Phrao, Bangkok, 10230, TH
Telephone: +66 2 124 5414
Price range: $$$$

EPC (Engineering-Procurement-Construction) lets you own your solar system outright — this guide covers everything Thai factory owners need to decide

4-7yr Payback30-60% SavingsBOI 8yr Tax Free

Published 2026-05-14 · Last updated 2026-05-14 · Reviewed by the CapSolar Team

18 min read

What Is EPC? Understanding Engineering-Procurement-Construction

EPC stands for Engineering, Procurement, and Construction. It is a solar installation model where you invest in and own the entire system from day one. The EPC contractor handles everything from system design and equipment sourcing to installation and commissioning — like building a turnkey solar power plant on your factory roof.

What clearly sets EPC apart from other models is ownership — you own the system, and you get free electricity from sunlight for 25-30 years (after the 4-7 year payback period). With a PPA (Power Purchase Agreement), you pay monthly electricity fees to the investor for the entire 15-25 year contract without ever owning the system.

EPC = You invest, you own it, you get free power for 25 years

Why Should Thai Factories Choose EPC in 2026?

Thai industrial electricity sits at 3.95 THB/kWh (May-Aug 2026, Ft 0.1623 THB) with a persistent upward trend. The higher the rate climbs, the faster EPC pays back — because every kWh your solar system generates is money you do not pay to the utility.

Rising Rates: 3.95 THB/kWh

The Ft surcharge has risen three consecutive periods. Industrial rates hit 3.95 THB/kWh (May-Aug 2026). EPC locks your electricity cost at zero after payback, compared to PPA where you still pay the provider throughout the contract.

BOI 8-Year Tax Exemption

Activity 5.4 (Solar Power) gets 8-year corporate income tax exemption + 0% import duty on equipment. Factories in EEC zones get an additional +50% cap on exemptions — these benefits can cut payback by 1-2 years.

25+ Year Asset Ownership

Solar panels last 25-30 years (0.5% annual degradation). After 4-7 year payback, you get free electricity for another 18-26 years — total value 3-5x your initial investment. The system is also a balance-sheet asset.

Lowest LCOE: 1.2 THB/kWh

The Levelized Cost of Energy (LCOE) for EPC solar is 1.20-1.35 THB/kWh compared to grid electricity at 3.95 THB/kWh — 65-70% cheaper. As grid rates rise, the gap only widens.

Current industrial electricity rate (May-Aug 2026)

3.95 THB/kWh

Solar EPC Process — 6 Steps From Start to Power-On

The full EPC process takes roughly 3-6 months depending on system size. A good EPC contractor manages every step for you — from site assessment to handing over a ready-to-use system.

01Site Assessment

1-2 weeks

Engineers survey the roof, check structural integrity, measure area, assess sunlight exposure, analyze 12 months of electricity bills, and determine the optimal system size.

02System Design (Engineering)

2-3 weeks

Design panel layout, select inverters, calculate string configuration, run shadow analysis, simulate production with software, prepare financial plan with ROI, IRR, and NPV projections.

03Equipment Procurement

2-4 weeks

Procure solar panels, inverters, mounting systems, cables, and electrical equipment. Select Tier-1 brands with long warranties. Verify specifications before ordering.

04Installation (Construction)

4-8 weeks

Install mounting rails, place solar panels, run cables, install inverters and distribution boards. Work is mostly on the roof — minimal disruption to factory operations.

05Testing & Commissioning

2-4 weeks

Test the entire system, submit PEA/MEA interconnection permits, connect to grid, verify meters, test safety systems. The system must pass standards before going live.

06Handover & O&M

Ongoing 25+ years

Hand over the system with complete documentation, user manual, warranties, and O&M contract. Real-time monitoring lets you track production 24/7.

Total timeline: 3-6 months

Solar EPC Cost & ROI for Factories

Real numbers for a 1 MW rooftop system — the sweet spot for medium-to-large factories with 3,000-5,000 sqm of roof area.

System Size

1 MW

EPC Investment

25-35M THB

Annual Savings

4-6M THB

Payback Period

4-7 years

IRR

15-25%

25-Year Net Profit

60-100M THB

Payback Period: 4-7 years25-Year Net Profit: 60-100M THB

Calculate ROI for Your Factory

BOI Benefits for Solar EPC — 8-Year Tax Exemption

The Board of Investment (BOI) classifies solar under Activity 5.4 (Solar Power), which receives the highest level of benefits. For factories investing in EPC systems, these incentives can reduce the payback period by 1-2 years.

8-Year CIT Exemption

Corporate income tax (CIT) exemption for 8 years — uncapped for projects > 1 MW, or capped proportionally for smaller projects. Profits from electricity savings are tax-free for the first 8 years.

0% Import Duty on Equipment

Solar equipment (panels, inverters, mounting systems) imported under BOI gets duty-free treatment, reducing equipment costs by 5-10%.

EEC +50% Bonus Cap

Factories in EEC zones (Chonburi, Rayong, Chachoengsao) receive an additional +50% investment-to-cap ratio on tax exemptions, making the tax benefits even more valuable.

1.5x Depreciation

You can claim 1.5x accelerated depreciation on the solar system in year one, significantly reducing your tax base in the year of investment.

Read the full 2026 BOI solar incentives guide

EPC vs PPA vs Lease — 3-Way Comparison

Each model has its own strengths. There is no single "best" option — it depends on your factory's financial position, goals, and risk tolerance.

Dimension	EPC (Buy)	PPA (Buy Power)	Lease
Upfront Investment	25-35M THB (1MW)	0 THB	0 THB
Ownership	100% yours	Provider owns	Lessor owns
Electricity Savings	30-60% (more after payback)	10-30%	15-35%
Payback	4-7 years	N/A (no investment)	N/A (monthly rental)
Risk	Owner bears risk	Provider bears risk	Shared
Best For	Have budget, want max ROI	No budget, want instant savings	Want flexibility, shorter terms

PPA vs EPC 12-dimension comparison EPC vs Lease vs PPA 15-dimension

How to Choose a Reliable Solar EPC Provider

An EPC provider is not just building a solar system — they are building an asset that must perform for 25+ years. Choosing the wrong provider can mean underperforming output, frequent issues, or expensive repairs.

Track Record: MWp + Real Case Studies

Check actual MWp installed, ask for completed project references, visit live installations if possible, and speak with past clients.

Warranty + O&M Contract

Panels must have >=12yr product + >=25yr performance warranty. Inverters >=5yr. Ask about O&M: cleaning frequency, response time for issues, monitoring system.

Licenses & Certifications

Verify electrical contractor license, ISO certification, licensed electrical engineers, experience with PEA/MEA/BOI processes. CapSolar has licensed electrical engineers and handles BOI applications for clients.

Price Transparency

A good provider breaks down the BOM (Bill of Materials) clearly — separating panel, inverter, mounting, labor, and other costs. No hidden fees bundled into a lump sum.

Compare 10 factory solar companies in Thailand

FAQ

Written and Reviewed by the CapSolar Team

Written by CapSolar's in-house engineering and advisory team — 16.5 MWp installed across 8 sites in Thailand, 15+ years combined team experience. Specializing in industrial rooftop EPC design, BOI application support, and C&I PPA structuring.

Technical review: CapSolar Engineering Lead (licensed electrical engineer, Thailand).

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