GrowShop editorial guide
What are grow LEDs, PPFD, and DLI?
Watts describe electricity use, not the light a plant receives. Distribution, distance, photoperiod, and growing area must be considered together.
Published: Updated:
Core terms
| Term | What it describes | Sufficient on its own? |
|---|---|---|
| Watt | Fixture electricity use | No |
| PPFD | Photosynthetic photon density reaching a surface each second | Needs a map and test conditions |
| Photoperiod | Daily time the light is on | Assess with plant type and growth stage |
| DLI | Accumulated photosynthetic light over a day | Requires PPFD and duration |
When comparing products
One centre-point PPFD value does not describe distribution across the whole growing area.
- Is measurement height and coverage stated?
- Was the PPFD map made under comparable conditions?
- Are heat management and safety documents provided?
- Are hanging distance and photoperiod recommendations separated by plant type?
- Are warranty and driver details written down?
Distance and uniformity
Moving a fixture closer can increase intensity at some points while changing coverage and uniformity. Treat the manufacturer's distance guidance as a starting point and check plant response with an appropriate light measurement.
Sources
Technical explanations on this page are independent summaries based on the institutional sources below.
Editorial method
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