"LED vs HPS" is the long-running grower argument over which light type produces the best cannabis. Two questions get mixed together. Efficiency is settled: modern LEDs deliver about 2.5–3 µmol/J against roughly 1.7–2.1 for HPS, so they give the same photons for less power and heat (Kusuma, Pattison and Bugbee 2020). Established. Final quality (aroma, resin, density, taste) at the same light level is not settled.
In practice
Switching from HPS to LED is not a like-for-like swap. LED canopies receive less radiant heat, so leaf temperature runs lower at the same air temperature (Nelson and Bugbee 2015). Growers who keep their HPS room settings often see slower growth and blame the light. Raise air temperature 1–3 °C (2–5 °F) and re-check leaf VPD. Irrigation needs also change because transpiration falls.
Many reports of "HPS buds are better" come from comparisons that changed several things at once: intensity, temperature, cultivar or grower experience.
Don't confuse with
- Spectrum differences: part of the comparison, but intensity and leaf temperature usually matter more.
- Wattage: compare µmol/s and µmol/J, not watts.
Myth check
GenetixBay's house position: "perhaps". Quality differences between LED and HPS are an open Bay Trial. The plan is a proper controlled study (same cultivar and clone source, matched PPFD and leaf VPD, blind evaluation) to settle it. Until then it is Contested. Follow the trial in Mythbusters.
