With HPS, heat was the biggest limit, anything above ~1000 µmol/m²/s would overheat the room. LEDs changed that. Today, even hobby growers can use high light levels without heat stress, so the real question is no longer “How much can I run?” but “How much light is ideal?”
What influences the right light intensity?
Plant type
Leaf crops (like basil or lettuce) need much less light than fruiting crops.
Light duration
Short‑day plants flower at 12 h of light. Since less time = less total light, flowering usually requires a higher PPFD than veg to maintain the same daily amount of light.
Environment & plant health
More light only works if temperature, CO₂, nutrients, and humidity are in balance. Higher PPFD = faster metabolism = higher demand.
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