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Excerpt: Choosing the right solar system size for your Thai factory? Compare costs, savings, and ROI for 50kW, 200kW, and 1MW+ systems with real Thailand electricity rate data and case studies.
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Here’s a problem we see almost every week at Red Solar: a factory owner calls us, excited about going solar, and asks the same question — “What size system do I need?”
It sounds simple. But get it wrong, and you either leave money on the table or tie up capital in panels you don’t need. Get it right, and you set up a system that pays for itself in three to four years and prints savings for the next two decades.
This guide breaks down the three most common solar system sizes we install for Thai factories — 50kW, 200kW, and 1MW+ — with real numbers based on Thailand’s current electricity rates, typical commercial TOU tariffs, and actual project experience across Rayong, Chonburi, Bangkok, and the Eastern Economic Corridor.
If you’re a factory owner, facility manager, or operations director in Thailand trying to figure out what makes sense for your situation, this is the article for you.
Why System Size Matters More Than You Think
Solar isn’t one-size-fits-all. A 50kW system on a small workshop in Samut Prakan behaves very differently from a 1MW installation on a food processing plant in Amata City. The differences aren’t just about scale — they affect your payback timeline, the financing options available to you, the rooftop space you’ll consume, and even the business model that works best.
At Red Solar, we’ve completed over 200 projects across Thailand, and the single biggest mistake we see is mismatched sizing. Some factories install systems that are too small to meaningfully offset their electricity bills. Others go too big, generate excess power they can’t use (remember, Thailand doesn’t have widespread net metering for commercial users yet), and end up with a lower effective return.
The right system size is the one that closely matches your actual daytime electricity consumption pattern, fits your available rooftop space, and aligns with your capital availability. Let’s look at each size tier in detail.
50kW Solar System: The Small Factory Starter
Who Is This For?
A 50kW solar system is the entry-level sweet spot for small manufacturing operations in Thailand. Typical customers include:
These businesses typically have monthly electricity bills between THB 80,000 and THB 200,000 under the MEA (Metropolitan Electricity Authority) or PEA (Provincial Electricity Authority) tariff structures. Their daytime load profile shows consistent consumption between 40kW and 60kW during business hours, making a 50kW solar system a near-perfect match.
Rooftop Space Requirements
A 50kW system using modern 550W monocrystalline panels requires approximately 92 panels. With proper spacing for maintenance access and row-to-row shading avoidance (critical in Thailand’s latitude of 13-15°N), you’ll need roughly 300-350 square meters of clear rooftop area.
Most small factory buildings in Thailand — typical dimensions of 20m × 30m or similar — easily accommodate this. A single warehouse bay or even a large office building rooftop can host a 50kW system without major structural modifications.
Installation Cost in Thailand (2026)
Based on current market pricing from Red Solar’s own factory-direct supply chain in Rayong:
Cost Component | Amount (THB)
—|—
Solar panels (92 × 550W monocrystalline, factory-direct) | 460,000 – 550,000
Inverters (hybrid or string inverter) | 80,000 – 120,000
Mounting structure (aluminum, corrosion-resistant for Thai climate) | 60,000 – 80,000
Electrical components, cabling, protection devices | 40,000 – 60,000
Installation labor and commissioning | 80,000 – 120,000
Permits, MEA/PEA interconnection approval | 15,000 – 25,000
Total | 735,000 – 955,000
For budgeting purposes, expect THB 750,000 to THB 1,000,000 for a complete, turnkey 50kW installation in Thailand. The variation depends on rooftop complexity, distance from the Rayong factory to the installation site, and whether structural reinforcement is needed.
Annual Energy Production
Thailand’s solar resource is genuinely excellent. Using PVsyst simulations with actual meteorological data from the Meteorological Department of Thailand:
Location | Annual Production (kWh) | Performance Ratio
—|—|—
Rayong (Eastern seaboard) | 73,000 – 76,000 | 80-82%
Bangkok (Central) | 70,000 – 73,000 | 78-80%
Chiang Mai (Northern) | 72,000 – 75,000 | 79-81%
Hat Yai (Southern) | 68,000 – 71,000 | 77-79%
The eastern seaboard — where most of Thailand’s manufacturing is concentrated — benefits from the highest irradiation levels in the country, averaging 5.2-5.5 kWh/m²/day annually.
Financial Returns: The Numbers That Matter
Let’s use Rayong as an example, with a mid-range installation cost of THB 850,000 and annual production of 74,500 kWh:
Self-consumption savings: Assuming 90% self-consumption (67,050 kWh used directly during daytime), at an effective rate of THB 4.20/kWh (blended TOU rate for medium-sized TOU customers under PEA):
Payback period: THB 850,000 ÷ THB 300,980 = 2.8 years
25-year lifetime savings: THB 300,980 × 25 years = THB 7,524,500, minus THB 850,000 investment = THB 6,674,500 net savings
That’s a lifetime ROI of nearly 785%. Not bad for a system that fits on a single small warehouse rooftop.
Best Business Model for 50kW Systems
For a 50kW system, the self-investment (EPC turnkey) model usually works best. The capital requirement is manageable for most small factory owners — and some Thai banks like KBank and SCB offer green energy loans with rates as low as 3.5-5% per annum, which we covered in our recent solar financing guide.
EMC (energy management contract) is also viable for 50kW systems, but many EMC developers prefer larger projects because the due diligence, legal, and administrative overhead is similar regardless of system size. If you want zero upfront cost, Red Solar does offer EMC for 50kW — just expect a slightly higher minimum contract duration.
200kW Solar System: The Mid-Range Workhorse
Who Is This For?
The 200kW system is, in our experience, the most popular size tier for medium-sized factories in Thailand. Typical customers include:
These businesses typically have monthly electricity bills between THB 300,000 and THB 800,000. They operate on high-voltage TOU tariffs (33kV or higher) with peak rates reaching THB 5.50-6.00/kWh during weekday daytime hours — exactly when solar panels produce their maximum output.
Rooftop Space Requirements
A 200kW system requires approximately 364 panels at 550W each. You’ll need roughly 1,100-1,300 square meters of clear rooftop area.
This fits comfortably on most medium factory buildings. A typical manufacturing facility of 40m × 50m (2,000 m²) can accommodate a 200kW system on roughly half the rooftop, leaving the other half available for future expansion, skylights, or HVAC equipment.
Structural assessment is more important at this scale. Most Thai factory roofs — typically metal deck with steel frame construction — can support the additional 12-15 kg/m² load from solar panels and mounting hardware, but a professional structural engineer should verify this before proceeding.
Installation Cost in Thailand (2026)
Economies of scale start kicking in at the 200kW level:
Cost Component | Amount (THB)
—|—
Solar panels (364 × 550W monocrystalline) | 1,820,000 – 2,200,000
Inverters (multiple string inverters or central inverter) | 280,000 – 380,000
Mounting structure | 220,000 – 300,000
Electrical components, cabling, protection devices | 150,000 – 220,000
Installation labor and commissioning | 250,000 – 350,000
Permits, MEA/PEA interconnection, engineering studies | 50,000 – 80,000
Total | 2,770,000 – 3,530,000
Budget THB 2.8 million to THB 3.5 million for a complete turnkey 200kW installation. The cost per watt drops from approximately THB 17/watt at 50kW to around THB 14-17/watt at 200kW — a meaningful saving driven by volume pricing on panels and more efficient installation workflows.
Annual Energy Production
For a 200kW system in Rayong:
Location | Annual Production (kWh) | Capacity Factor
—|—|—
Rayong | 292,000 – 304,000 | 16.7-17.4%
Bangkok | 280,000 – 292,000 | 16.0-16.7%
Chonburi (EEC) | 290,000 – 302,000 | 16.6-17.3%
Nakhon Ratchasima | 285,000 – 298,000 | 16.3-17.0%
Financial Returns
Using Rayong figures with a mid-range cost of THB 3,150,000 and annual production of 298,000 kWh:
Self-consumption savings: At 85% self-consumption (253,300 kWh), with a medium-voltage TOU peak rate of THB 5.20/kWh:
Payback period: THB 3,150,000 ÷ THB 1,433,380 = 2.2 years
Notice the payback is faster than the 50kW system — not just because of lower per-watt costs, but because 200kW systems typically serve higher-voltage customers with more expensive peak-time electricity rates. Every kWh you offset at THB 5.20 saves more than every kWh offset at THB 4.20.
25-year lifetime savings: THB 1,433,380 × 25 = THB 35,834,500, minus THB 3,150,000 = THB 32,684,500 net savings
That’s over THB 32 million in net savings from a single rooftop installation.
Real Case: Chonburi Electronics Assembly Plant
Last year, Red Solar installed a 200kW system on an electronics assembly facility in the Amata Nakorn Industrial Estate, Chonburi. The factory had a monthly electricity bill of approximately THB 520,000 under the PEA high-voltage TOU tariff.
Here’s what the system delivered in its first 12 months of operation:
The factory manager told us the most surprising part wasn’t the savings — it was how little disruption the installation caused. Our crew worked around their production schedule, and the entire 200kW system was installed and commissioned in just five weeks.
For this customer, the EMC model was the financing path they chose — zero upfront cost, immediate 15% discount on solar electricity from day one. If you want to understand how EMC compares to self-investment at this scale, our business models guide breaks down all four options with real numbers.
Best Business Model for 200kW Systems
At 200kW, both self-investment and EMC make excellent sense. Self-investment gives you the fastest payback and highest lifetime return. EMC gives you zero upfront cost and immediate savings from month one. The right choice depends on your capital situation and risk tolerance.
Many Chinese-owned factories in Thailand prefer the self-investment model because the decision chain is short — the owner sees the numbers, approves the budget, and construction starts within weeks. Thai-owned factories sometimes prefer EMC because it avoids the capital expenditure approval process and board-level sign-off.
1MW+ Solar System: The Industrial-Scale Investment
Who Is This For?
A 1MW (megawatt) or larger solar system is for serious industrial operations. Typical customers include:
These facilities typically have monthly electricity bills exceeding THB 1 million, and many operate under the very large user (VLU) tariff category with demand charges that can add THB 200,000-500,000 per month on top of energy charges.
Rooftop Space Requirements
A 1MW system requires approximately 1,820 panels at 550W each. You’ll need 5,500-6,500 square meters of clear rooftop area.
This is where rooftop availability becomes a genuine constraint. Many large Thai factories have expansive roofs, but they’re often partially occupied by skylights, HVAC equipment, exhaust systems, and crane structures. We frequently find that a factory with a 10,000 m² roof can practically accommodate 800kW-1.2MW of solar panels after accounting for these obstructions and maintaining required fire egress pathways.
For facilities with insufficient single-roof space, we sometimes design systems across multiple buildings — the main production hall, warehouse, and administrative building — connected through a shared inverter and electrical distribution system.
Installation Cost in Thailand (2026)
At the 1MW scale, economies of scale are significant:
Cost Component | Amount (THB)
—|—
Solar panels (1,820 × 550W monocrystalline) | 9,100,000 – 11,000,000
Inverters (central inverters or large string arrays) | 1,200,000 – 1,600,000
Mounting structure | 1,000,000 – 1,400,000
Electrical components, cabling, protection devices, transformers | 700,000 – 1,000,000
Installation labor and commissioning | 1,000,000 – 1,500,000
Engineering studies, permits, PEA/MEA interconnection, structural analysis | 200,000 – 350,000
Total | 13,200,000 – 16,850,000
Budget THB 13 million to THB 17 million for a complete turnkey 1MW installation. The cost per watt drops further to approximately THB 13-17/watt at this scale.
For systems above 1MW (we regularly install 1.5MW, 2MW, and even 3MW systems), the per-watt cost continues to decrease, but structural reinforcement and electrical infrastructure upgrades may add costs that partially offset the volume savings.
Annual Energy Production
For a 1MW system in Rayong:
Location | Annual Production (kWh) | Capacity Factor
—|—|—
Rayong | 1,460,000 – 1,520,000 | 16.7-17.4%
Bangkok | 1,400,000 – 1,460,000 | 16.0-16.7%
Chonburi (EEC) | 1,450,000 – 1,510,000 | 16.5-17.2%
Lam Chabang (port area) | 1,470,000 – 1,530,000 | 16.8-17.5%
Financial Returns
Using Rayong figures with a mid-range cost of THB 15,000,000 and annual production of 1,490,000 kWh:
Self-consumption savings: At 80% self-consumption (1,192,000 kWh), with a large-user TOU peak rate of THB 5.50/kWh:
Payback period: THB 15,000,000 ÷ THB 7,330,800 = 2.0 years
The payback at 1MW is the fastest of all three tiers, driven by the combination of lowest per-watt installation costs and highest applicable electricity rates (large users pay the most per kWh, so every offset kWh saves the most).
25-year lifetime savings: THB 7,330,800 × 25 = THB 183,270,000, minus THB 15,000,000 = THB 168,270,000 net savings
That’s THB 168 million in net savings — from one rooftop.
Real Case: Rayong Food Processing Plant (1.2MW)
Our largest single-rooftop installation to date is a 1.2MW system on a food processing plant in the Rayong Industrial Estate. This case is detailed in our full case study, but the key numbers are worth repeating:
The factory processes frozen seafood for export, meaning they run refrigeration compressors 24/7. Their daytime load consistently exceeds 1MW, making a 1.2MW solar system an almost perfect match for their consumption profile. The system offset 78% of their daytime electricity consumption in the first year of operation.
Best Business Model for 1MW+ Systems
At the 1MW+ scale, the choice of business model becomes a strategic financial decision, not just an operational one:
Side-by-Side Comparison: All Three Sizes at a Glance
Metric | 50kW System | 200kW System | 1MW System
—|—|—|—
Typical factory size | Small (10-30 employees) | Medium (50-200 employees) | Large (200-1,000+ employees)
Monthly electricity bill | THB 80,000-200,000 | THB 300,000-800,000 | THB 1,000,000+
Installation cost | THB 750K-1M | THB 2.8M-3.5M | THB 13M-17M
Cost per watt | ~THB 17/W | ~THB 14-17/W | ~THB 13-17/W
Rooftop area needed | 300-350 m² | 1,100-1,300 m² | 5,500-6,500 m²
Annual production (Rayong) | 73,000-76,000 kWh | 292,000-304,000 kWh | 1,460,000-1,520,000 kWh
Self-consumption rate | ~90% | ~85% | ~80%
Annual savings | ~THB 301,000 | ~THB 1,433,000 | ~THB 7,331,000
Payback period | 2.8 years | 2.2 years | 2.0 years
25-year net savings | THB 6.7M | THB 32.7M | THB 168.3M
CO₂ reduction/year | ~60 metric tons | ~237 metric tons | ~1,192 metric tons
Installation timeline | 2-3 weeks | 4-6 weeks | 8-12 weeks
How to Decide: A Practical Framework
So which size is right for your factory? Here’s the decision framework we use with every client:
Step 1: Analyze Your Electricity Bills
Pull your last 12 months of PEA or MEA bills. Look for three things:
1. Total monthly consumption (kWh) — this tells you how much electricity you use
2. Peak vs. off-peak split — under TOU tariffs, peak-time electricity (weekday 9:00-22:00) costs significantly more. Solar offsets peak-time consumption first, so the higher your peak usage percentage, the better solar works for you
3. Demand charges — if you’re on a tariff with demand charges (THB per kW of peak demand), solar can help reduce these too by lowering your peak grid draw
If you’re not sure how to read your Thai electricity bill for solar planning, our guide on Thailand TOU tariffs explains the rate structure in detail.
Step 2: Assess Your Rooftop
Walk your rooftop (or have your facilities manager do it) and measure the clear, unobstructed area. Subtract space needed for:
The remaining usable area, divided by approximately 3.2 m² per panel (including spacing), gives you your maximum panel count. Multiply by 0.55kW per panel for your maximum system size.
Step 3: Match Consumption to Production
This is the critical step. Your goal is to size the system so that it produces roughly 70-90% of your daytime electricity consumption. Why not 100%?
Because Thailand’s commercial net metering program is still limited. Any solar electricity you generate but can’t use during the day gets exported to the grid at the feed-in tariff rate (around THB 2.60/kWh), which is significantly lower than what you pay to buy electricity. Oversizing your system means you’re effectively selling electricity at a loss.
A well-sized system maximizes self-consumption and minimizes export — every panel works to directly offset your most expensive grid electricity.
Step 4: Choose Your Financing Path
Once you know the right system size, pick the business model that fits your situation:
Our complete guide to solar business models in Thailand covers all four options with detailed comparisons.
What About Future Expansion?
One question we hear constantly: “Can I start with 200kW and expand to 1MW later?”
The short answer is yes — but it requires planning from day one. If you think you might expand, tell your solar installer during the initial design phase. They can:
Adding 5-10% to the initial engineering and permitting cost to design for future expansion is almost always worth it. We’ve had multiple clients start with 200kW and expand to 500kW or 1MW within 2-3 years as their confidence in the system’s performance grew.
Ready to Find Your Right Size?
The best way to determine the optimal solar system size for your factory is with a professional site assessment and energy analysis. At Red Solar, we provide this assessment free of charge — our engineering team visits your facility, measures your rooftop, analyzes your electricity bills, and delivers a detailed proposal with system design, production estimates, financial projections, and recommended business model.
If your factory is located in one of Thailand’s major industrial estates — Amata, WHA, or any of the EEC zones — we likely have existing installations in the same area, which can simplify permitting and interconnection.
Contact Red Solar for a free solar assessment — or call us directly at +66 (0) 62-106-6696. We’re based in Rayong, right in the heart of Thailand’s industrial corridor, and we’re ready to help you make the right solar investment decision.
