# LED vs HPS

> LED vs HPS is the debate over whether LED or high-pressure sodium lights grow better cannabis; LEDs are clearly more efficient, while final-quality differences remain an open question.

- Canonical: https://genetixbay.com/knowledge/glossary/led-vs-hps.html
- Also written: LED versus HPS, HPS vs LED, LED or HPS, LED vs HID
- Glossary category: Environment and light · Evidence: Contested
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

"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](https://genetixbay.com/knowledge/glossary/led.md) deliver about 2.5–3 [µmol/J](https://genetixbay.com/knowledge/glossary/photon-efficacy.md) against roughly 1.7–2.1 for [HPS](https://genetixbay.com/knowledge/glossary/hps.md), 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](https://genetixbay.com/knowledge/glossary/leaf-temperature.md) 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](https://genetixbay.com/knowledge/glossary/vpd.md). Irrigation needs also change because [transpiration](https://genetixbay.com/knowledge/glossary/transpiration.md) 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](https://genetixbay.com/knowledge/glossary/bay-trials.md)**. The plan is a proper controlled study (same cultivar and clone source, matched [PPFD](https://genetixbay.com/knowledge/glossary/ppfd.md) and leaf VPD, blind evaluation) to settle it. Until then it is *Contested*. Follow the trial in [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md).

## Related terms

[LED](https://genetixbay.com/knowledge/glossary/led.md), [HPS](https://genetixbay.com/knowledge/glossary/hps.md), [Photon efficacy](https://genetixbay.com/knowledge/glossary/photon-efficacy.md), [Leaf temperature](https://genetixbay.com/knowledge/glossary/leaf-temperature.md)

## Read more

- [Light spectrum: blue, red, far-red and UV, what's real](https://genetixbay.com/knowledge/environment/light-spectrum.md)
- [Heat and light stress: taco leaves, bleaching and foxtails](https://genetixbay.com/knowledge/environment/heat-light-stress.md)

## Sources

1. Kusuma P, Pattison PM, Bugbee B, 2020. From physics to fixtures to food: current and potential LED efficacy. Horticulture Research 7:56. https://doi.org/10.1038/s41438-020-0283-7
2. Nelson JA, Bugbee B, 2015. Analysis of environmental effects on leaf temperature under sunlight, high pressure sodium and light emitting diodes. PLoS ONE 10(10): e0138930. https://pmc.ncbi.nlm.nih.gov/articles/PMC4598144/
3. Westmoreland FM, Kusuma P, Bugbee B, 2021. Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids. PLoS ONE 16(3): e0248988. https://doi.org/10.1371/journal.pone.0248988