What Is CCT?
Definition, standards, typical values, applications and the procurement checks for CCT.
🕒 Updated 2026-09-17 · 🧾 Verified by the CompareDeals lighting team
Definition
CCT is one of the specifications that decides whether a lighting project is accepted at handover or argued about for a year.
CCT is a measured performance figure that lets a buyer place different suppliers on one ruler.
The number is only meaningful together with its test condition: ambient temperature, drive current, optical system and the standard used.
How Does It Work — CCT
The value is measured in an integrating sphere or goniophotometer after 30 minutes of stabilisation at 25 ± 1 °C.
Every layer between the bare emitter and the finished luminaire changes the figure: optics cost roughly 10-20%, the driver 8-12%.
Batch consistency depends on staying in one emitter bin and one driver platform; changing either requires a new sample round.
Key Data: Specifications & Standards
MacAdam 5-step (SDCM ≤ 5) between fixtures on one project; 3-step for retail displays
| Parameter | Value / level | Explanation |
|---|---|---|
| 2700K | Warm white | Hospitality, residential, evening retail |
| 3000K | Warm white | Hotel, restaurant, premium retail |
| 3500K | Neutral | Office, healthcare, mixed-use |
| 4000K | Cool white | Warehouse, factory, supermarket, exterior |
| 5000K | Daylight | Inspection, sports, cold storage |
| 5700-6500K | Daylight plus | Horticulture, industrial inspection |
Reference standard: ANSI C78.377
Applications: Where It Fits
CCT appears in the design document, the purchase order and the acceptance test; all three must quote the same figure with the same condition.
When the three documents disagree, the usual outcome is a compliant fixture inside a project that fails inspection.
Comparison to Alternatives
| Criterion | This metric | The metric buyers confuse with it | Whole-system view |
|---|---|---|---|
| What it measures | One photometric or electrical property | A neighbouring property | Performance delivered in the room |
| Typical tolerance | ±5% at the rated condition | Often quoted with no condition | ±10% after optics and dirt depreciation |
| Fails when | The test condition is missing | It is used as a substitute for the real requirement | Uniformity or glare is ignored |
| How to specify it | Value + standard + condition | Value + why it matters | Simulation at the real mounting height |
Common Pitfalls and Specification Rules
Request the LM-79 / LM-80 report and the raw sphere data, not the marketing figure.
Two 4000K luminaires from different bins can read 500K apart on a white wall. Lock the SDCM and state the bin on the PO.
- Check that the model in the report matches the model being shipped.
- Sample-test the first shipment at a third-party lab and put the tolerance into the quality agreement.
Conclusion & Procurement Recommendation
4000K is the default for industrial space; 3000K for hospitality; keep one CCT per continuous view.
When the specification is loose, the factory optimises for cost and the difference only appears after installation.
🔑 Key Takeaways
- CCT is only meaningful together with its test condition.
- Put the value, the standard and the tolerance into the purchase order and the quality agreement.
- Sample-test the first shipment at a third party: it costs far less than rework.
- Keep one emitter bin and one driver platform across the whole project.
Frequently Asked Questions
What is a normal compliant value for CCT?
4000K is the default for industrial space; 3000K for hospitality; keep one CCT per continuous view. Most commercial projects sit in the standard tier; only a stated requirement justifies moving up.
How can I verify the figure a supplier quotes?
Ask for the report against ANSI C78.377 and check that the model on the report matches the model being shipped.
How much does CCT vary between batches?
Batch consistency depends on keeping one emitter bin and one driver platform. Change either and you must re-sample.
How should this be written into the purchase order?
Value + standard + test condition + tolerance band. Miss any one of the four and the supplier has room to interpret.
What if the project is already under construction?
Test on site, quantify the deviation, then decide between rework, adjustment or acceptance and record the decision.
📋 Sources & Verification
| Manufacturer datasheet | Nominal values and installation conditions |
|---|---|
| ANSI C78.377 | Test method and pass criteria |
| Third-party laboratory report | Measured performance and deviation |
| Platform verification record | Certificate number cross-checked with the issuer |
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