Factory Solar Procurement Checklist Thailand: 20-Point RFP Guide Before Signing

Why Comparing Solar Quotes Is Harder Than It Looks

Most factories collect 2-5 quotes. The documents look similar but hide 3 critical traps: (1) System sizes differ — one quotes DC/AC ratio 1.1, another 1.3, producing different outputs at similar prices. (2) Scope varies — some include roof reinforcement, others exclude it, inflating real costs 15-20% above the quoted price. (3) Warranty terms diverge — a 25-year warranty can mean vastly different degradation guarantees. Before comparing prices, align the 'product' first — that is the purpose of this 20-point checklist. See current solar panel pricing for market ranges before you compare, and read how to vet a solar installer and avoid scams to catch quotes designed to mislead. For a worked example of a scope that names design, installation and long-term care in one document, see how our factory solar services are structured.

The 20-Point Solar Procurement Checklist

Use this checklist against every quote. If a vendor does not clearly specify an item, ask. If you spot a red flag, proceed with caution. (If you are not yet familiar with electricity bill structure, start with our factory bill anatomy guide.)

Deep-Dive: Technical Specification (Items 1-5)

Tier-1 panels (LONGi, JA Solar, Trina, Canadian Solar, Jinko) degrade at 0.4-0.55%/yr, producing ~87% of rated output at year 25. Off-list brands at 0.6-0.8%/yr drop to ~80% — a ~7% cumulative gap. Over 25 years for a 1 MW system, that equals ~700 MWh or ~2.8M THB (at 4 THB/kWh). DC/AC ratio 1.2 means a 1 MW AC inverter paired with 1.2 MWp DC panels — 20% panel oversizing to maximize morning/evening production. Below 1.1 = underbuilt, losing generation potential. Above 1.3 causes clipping loss (inverter curtails excess). For panel pricing per tier, see the pricing page. Roof structures must support 12-15 kg/sqm + wind load — typical factory roofs handle 30-50 kg/sqm, but roofs > 15 years old need structural engineer review. Realistic PR in Thailand (PVOUT 1,490 kWh/kWp, high temperatures, dust) is 78-82%. Vendors claiming > 85% may be using lab or first-year figures, not 25-year averages.

Deep-Dive: Financial Terms (Items 6-10)

PPA rates in Thailand 2026 sit at 2.50-3.50 THB/kWh vs a PEA all-class average grid tariff of ~3.86 THB/kWh — 9-35% day-1 savings. But the escalation clause is the biggest risk: a 15-year PPA at 3%/yr escalation totals 25-30% more than a fixed rate. See PPA vs EPC comparison across 12 dimensions. For EPC, 2026 market pricing is 14-25 THB/Wp depending on size. See installed price per tier. Hidden costs to ask about: roof reinforcement (500K-2M THB), transformer upgrade (300K-1.5M), permits (50K-200K), insurance (0.3-0.5%/yr of CAPEX), monitoring subscription (20K-50K/yr). Try calculating your factory ROI before deciding.

Deep-Dive: Warranty, Performance Guarantee & Insurance (Items 11-14)

Product warranty vs Performance warranty differ: product warranty covers physical defects (delamination, junction box failure, cracking). Performance warranty guarantees degradation rate — output drops no more than X%/yr. PR guarantee + LD clause is the buyer's key weapon: if the system underperforms the promised PR, the vendor pays liquidated damages. Example: PR guarantee 80%, 1 MW system at PVOUT 1,300 kWh/kWp, actual PR only 75% = 5% shortfall x 1,300 MWh = 65 MWh/yr at ~4 THB/kWh = ~260K THB/yr compensation. For PPA vs EPC comparison with full warranty dimension, see the 12-dimension analysis.

How to Write a Solar RFP (Request for Proposal)

A good RFP forces vendors to answer every item in the 20-point checklist — enabling apple-to-apple comparison from round one. Structure an RFP in 6 parts: (1) Factory info: load profile, 12-month bills, roof drawings. (2) Scope: EPC or PPA, target size, timeline. (3) Minimum specs: Tier-1 panels, inverter brand list, PR guarantee, degradation limit. (4) Financial terms: payment milestones, escalation cap, bond requirements. (5) Scoring criteria: weight per dimension. (6) Submission deadline + Q&A channel. Total RFP timeline: 4-6 weeks from issuance to contract signing. Before you decide, run shortlisted bidders through the EPC vetting checklist to separate credible contractors from the rest. After selecting a vendor, see EPC guide for 6 post-signing steps, and plan your schedule around the factory solar installation timeline (sign → COD).

After Signing: 5 Key Milestones

Signing is not the end — here are 5 milestones to track. A 500kW system takes 6-8 weeks, 1MW takes 8-12 weeks, 3MW+ takes 12-16 weeks. Note: monsoon season (May-Oct) may add 2-4 weeks.

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