What Is RE100 — Understand in 40 Seconds
RE100 is an organization's commitment to source 100% of its electricity from renewables, proven through Renewable Energy Certificates (REC/IREC). For a Thai factory there are four main paths you can mix: your own rooftop solar, a Direct PPA, UGT2 (buying green power through the utility), and buying unbundled IRECs. The most cost-effective strategy is to start with rooftop solar (cheapest), then top up the rest with the other mechanisms until you reach 100%.
RE100 = 100% renewable electricity + provable with RECs → Strategy: rooftop first, then top up in layers
RE100 is a global initiative (led by the Climate Group with CDP) under which companies commit to 100% renewable electricity. The key to counting it correctly is that every unit of green power must carry a certificate (REC/IREC) to prevent double-counting, and it must sit within the same market boundary (for Thailand, that means I-REC). What confuses factory managers is not RE100 itself but where to source the green power, because each mechanism differs in cost, speed, and whether you get physical electricity or only a certificate. So this page lays them out as a decision sequence, not an either/or menu — in practice most factories use a mix of mechanisms.
Note: RE100 technical criteria (e.g. market boundary, vintage, additionality) are updated periodically — confirm the current RE100 / Climate Group criteria before finalizing your reporting plan.
The 4 Green-Power Options in Thailand — Overview
Before the table and the decision tree, here is a quick intro to all four mechanisms. Each has its own dedicated page with deeper detail (linked inside each card).
1. On-site Rooftop Solar (Your Own)
Install solar panels on your own factory roof. Lowest cost (LCOE ~2 THB/kWh), fast payback, and the power you generate counts as renewable immediately (RECs can be issued). Limits: daytime generation only, capped by available roof area — so it rarely reaches 100% on its own.
Full factory solar guide2. Direct PPA (Direct Power Purchase)
Negotiate to buy renewable power directly from a private generator, delivered over the grid (Third-Party Access) for a wheeling charge. Price is negotiable and often below grid. Best for large loads without enough roof — but it is more complex and takes time to negotiate.
Direct PPA factory guide3. UGT2 (Utility Green Tariff)
Buy renewable power directly through the MEA/PEA utility, with the REC bundled on one bill, on a 10-year contract. No negotiation, no roof needed. Rate ~4.55–4.56 THB/kWh (as reported 2026) — a premium. Best as the simplest way to green the grid-import you have left.
UGT2 factory guide4. Unbundled IRECs
Buy only the renewable-energy 'certificate' (I-REC) without receiving any physical power — you pay just the certificate fee. Use it to close the final paper gap to RE100. Cheapest per unit on a fee basis, but it does not cut your actual electricity bill or add new generation.
What is an IRECComparison Table — Cost, Roof, REC, Contract
The table below compares all four mechanisms on the dimensions buyers actually care about: capex needed, roof needed, physical power vs certificate only, RE100 validity, contract length, and best-fit scenario (figures are approximate as reported — see each mechanism's own page for detail and sources).
| Dimension | Rooftop solar | Direct PPA | UGT2 | IREC-only |
|---|---|---|---|---|
| Capex required | High (or 0 with rooftop PPA) | None (developer-owned) or low | None | None |
| Roof / land needed | Yes | Depends | No | No |
| Indicative cost | ~2 THB/kWh (LCOE) | Negotiated, often below grid | ~4.55–4.56 THB/kWh (reported) | Certificate fee only (no power) |
| Physical green power | Yes | Yes | Yes (bundled REC) | No — certificate only |
| RE100 / CDP valid | Yes (with REC) | Yes | Yes | Yes |
| Contract term | Asset life ~25 yr | Typically 10–25 yr | 10 yr | Per purchase |
| Best for (sequence) | Always do first — cheapest | Large load roof can't cover | Simplest top-up for grid-import | Closing the final paper gap |
Rates approximate, as reported 2026; UGT2 is set by the ERC — verify the current period. Solar/PPA cost depends on system size and site.
The Decision Tree — Layer Up Until You Reach RE100
This is the most important part of the page. Don't think of it as picking one mechanism — layer them, from the cheapest and highest-return to the more expensive. Most Thai factories end up mixing 2–3 mechanisms.
Layer 1 — Maximize rooftop solar first
Ask: 'How many kWp can my factory roof hold, and how much of my daytime load does it cover?' Because ~2 THB/kWh is the cheapest with the fastest payback, every self-generated unit cuts both your bill and your carbon. This should always be the first step.
Layer 2 — Still short with a big load? Consider Direct PPA
If the roof isn't enough and you have a load big enough to negotiate, a Direct PPA adds renewable power, often below the grid rate. Good if you have extra space (ground-mount/floating) or buy from a private solar farm over the grid — but be ready for contract complexity and a wheeling charge.
Layer 3 — Want it simple and fast? Use UGT2 for the rest
For the kWh still on the grid — especially night-time load or what rooftop/PPA can't reach — UGT2 converts it into verified green power through the utility bill, with no negotiation. The 10-year contract locks price and hedges fuel volatility. It's the 'easiest to deploy' way to close a real-power gap.
Layer 4 — A small remainder? Close it with IRECs
If after the three layers a small slice of grid-import still can't be greened (e.g. contract or site constraints), buy unbundled I-RECs to close the paper gap. Cheapest per unit on a fee basis, but remember it is a certificate — not physical power and it does not cut your bill — so it should be the last resort, not the first move.
Outcome: rooftop + (Direct PPA and/or UGT2) + IRECs to finish = RE100 at the lowest blended cost, because you've used the cheapest path as much as possible first.
Worked Example: How One Factory Reaches 100% RE
Suppose a factory uses 100 units of electricity per year (a proportion, for illustration). Here's how the layers stack up:
Total: 100% RE with 40% from the cheapest power (~2 THB) and only 5% bought as IRECs — a far lower blended cost than relying on UGT2 or IRECs alone. Your real split depends on your roof, load and site — CapSolar can model it for you.
How CapSolar Can Help
CapSolar designs and installs factory rooftop solar, backed by 80+ MWp / 150+ projects in Thailand, 100+ clients, and 85,000+ tons of CO₂ avoided. We don't just sell panels — we help you plan the whole road to RE100: maximize the roof first, then assess whether the remainder is best topped up with a Direct PPA, UGT2, or IRECs for your factory. Not sure where to start? Let us assess your roof and remaining grid-import for free.
Plan Your Factory's Road to RE100 — Start a Free Assessment
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