What Is Daylight Harvesting?
Definition, standards, typical values, applications and the procurement checks for Daylight Harvesting.
🕒 Updated 2026-09-17 · 🧾 Verified by the CompareDeals lighting team
Definition
Daylight Harvesting is one of the specifications that decides whether a lighting project is accepted at handover or argued about for a year.
Daylight Harvesting is the sensing device that turns presence, absence or ambient light into a switching or dimming command.
Its value is not the hardware price: it is the energy saved minus the cost of false triggers and the complaints they generate.
How Does It Work — Daylight Harvesting
The detection principle decides the application: PIR for lateral movement in corridors, microwave where penetration and micro-movement matter, ultrasonic for partitioned spaces.
Time delay and sensitivity must be set on site; factory defaults reliably produce either early switch-off or false triggers.
Daylight sensing needs a correct open-loop or closed-loop strategy, otherwise the fixture oscillates on a bright cloudy day.
Key Data: Specifications & Standards
| Parameter | Value / level | Explanation |
|---|
Reference standard: IEC / EN / IES series
Applications: Where It Fits
Daylight Harvesting 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 | PIR | Microwave | Ultrasonic |
|---|---|---|---|
| Detects | Lateral infrared movement | Movement, including through non-metallic surfaces | Air disturbance in enclosed space |
| Best space | Corridors, open offices, warehouses | Car parks, stairwells, cold stores | Partitioned restrooms and cubicles |
| Weakness | Heat sources and glass partitions | Detects through walls, false triggers | Airflow and draughts |
| Typical range | 8-12 m at 3 m mounting | 10-16 m adjustable | 6-9 m omnidirectional |
Common Pitfalls and Specification Rules
Check the detection pattern against the mounting height rather than a single "8 m diameter" claim.
- Confirm the adjustable delay and sensitivity range and whether the sensor dims rather than only switches.
- Ask for the assumptions behind the claimed energy saving.
Conclusion & Procurement Recommendation
Writing the target value and tolerance for Daylight Harvesting into the purchase document, then requiring the matching report, is the most direct way to control this risk.
When the specification is loose, the factory optimises for cost and the difference only appears after installation.
🔑 Key Takeaways
- Daylight Harvesting 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 Daylight Harvesting?
Write the target value for Daylight Harvesting into the purchase document, then require the matching test report. 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 the IEC / EN / IES standard and check that the model on the report matches the model being shipped.
How much does Daylight Harvesting 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 |
|---|---|
| IEC / EN / IES standard | 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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