Cannabis Grow Lights LED HPS CMH: Full 2026 Compare

Cannabis grow lights LED HPS CMH is a category of home cultivation equipment that lets indoor growers convert electricity into usable photosynthetic light for every stage of a tent grow. Pick a light source and you've picked your electricity bill, your tent temperature, your spectrum quality, and — honestly — half your yield ceiling. These three serious contenders for home tents each have real strengths, real trade-offs, and real growers who swear by them. Here's how they actually compare when you buy a fixture for a home setup.

LED vs HPS vs CMH at a glance

LED leads on efficacy, HPS wins on upfront cost, and CMH sits in the middle with the broadest spectrum. The table below summarises the key dimensions.

AZARIUS · LED vs HPS vs CMH at a glance

The metrics that actually matter

PPFD and DLI are the only light numbers worth tracking — lumens are for human eyes, not plants. Published cannabis research converges on roughly 400–600 PPFD in vegetative growth and 600–1,000 PPFD in flower, with the upper end only useful if you're running CO₂ supplementation (Chandra et al., 2008). Push past ~1,500 PPFD without CO₂ and photosynthesis plateaus while your plants cook.

AZARIUS · The metrics that actually matter

Efficacy — how many micromoles of photosynthetically active light a fixture produces per joule of electricity — is where LEDs have pulled ahead. A Fluence or equivalent bar-style LED at 2.7 μmol/J delivers roughly 50% more usable light per watt than a 600W HPS at 1.8 μmol/J. That's not marketing; it's a DLC-listed spec you can check on any reputable fixture's datasheet before you order.

LED: the current default for home tents

LED is the right first choice for most new home tents in 2026 because it combines class-leading efficacy with manageable heat. Modern horticultural LEDs — quantum board and bar-style fixtures using Samsung LM301H or LM301B diodes, or equivalents from Seoul Semiconductor and Osram — cover both veg and flower with full spectrum plus dedicated 660nm red diodes, and the efficacy numbers are genuinely class-leading.

AZARIUS · LED: the current default for home tents

The trade-offs are real though. Upfront cost is the highest of the three. Cheap Amazon "1000W" LEDs (which actually draw 100W) are a waste of money — look at the actual wall draw, diode brand, and driver (Meanwell or Sosen are the standards) before you buy. And LEDs don't throw much radiant heat downward, which means in a cold Dutch attic in January you'll need a heater where an HPS would have handled it. Some growers also report looser buds under pure LED compared to HPS in the same genetics, though this seems to resolve with proper intensity and end-of-flower UV supplementation.

HPS: the old champion, still swinging

HPS remains the cheapest reliable way to flower cannabis indoors, and the gram-per-watt numbers are still competitive with all but the best LEDs. High-pressure sodium has been the flowering standard since the 1980s and there's a reason it hung on so long: a Lumatek or Gavita 600W digital ballast plus a bulb and reflector is a small purchase compared to top-tier LED. The spectrum is heavy in the 580–620nm orange-red range, which photoperiod plants in flower genuinely respond to.

AZARIUS · HPS: the old champion, still swinging

The problems are heat and efficiency. A 600W HPS dumps around 2,000 BTU/hour into your tent. In a 1.2×1.2m tent in a warm room, you're fighting canopy temps above 30°C before you've even started. Bulbs also lose ~10% output per year and should be replaced annually if you're serious. And the spectrum is narrow — great for fattening flower, mediocre for vegging dense, short plants (which is why the classic pro setup runs MH or CMH in veg, HPS in flower).

CMH: the terpene nerd's choice

CMH is the fixture to get if resin quality and aroma matter more to you than raw yield. Ceramic metal halide (sometimes branded LEC, light-emitting ceramic) sits between HPS and LED on most axes. A 315W Philips CDM-T Elite or Sunmaster ceramic bulb produces a broad white spectrum with genuine UV-A output and trace UV-B — the wavelengths plants use to produce protective secondary metabolites, which includes trichome and terpene production.

AZARIUS · CMH: the terpene nerd's choice

One 315W CMH fixture covers roughly a 0.9×0.9m flowering footprint or a full 1.2×1.2m veg footprint. Two 315W units or a single 630W dual-bulb fixture handles a 1.2×1.2m flower tent nicely. Efficacy is better than HPS and worse than modern LED. Bulbs last around 20,000 hours before spectrum shift — longer than HPS, shorter than LED diodes.

Heat, electricity, and the Dutch attic problem

Heat is the single biggest reason EU home growers switch from HPS to LED. A 600W HPS in a 1.2×1.2m tent with a 150mm extraction fan can still hit canopy temps of 32°C on a warm summer day — well above the VPD sweet spot of 1.0–1.5 kPa for flowering. You can fight this with bigger fans, air-cooled reflectors, or moving to a cellar, but you're adding cost and noise.

AZARIUS · Heat, electricity, and the Dutch attic problem

Electricity-wise, on a typical Dutch 2026 tariff, a 600W HPS running 12 hours a day for a 9-week flower costs noticeably more to run than a 400W LED producing equivalent PPFD. Over two or three cycles a year, the LED upgrade pays back.

Which should you actually buy?

Most home growers should get a mid-range LED bar fixture from a reputable brand — it's the honest answer for small tents (60×60cm to 1.2×1.2m) running one or two cycles a year in a warm European apartment. Mars Hydro FC-series, Spider Farmer SF, Lumatek Zeus, or Fluence if budget allows all deliver efficacy, heat, lifespan, and full-cycle spectrum on the right side of the ledger.

AZARIUS · Which should you actually buy?

HPS still makes sense if you've got a cold room, a tight upfront budget, and you're only running the lamp in flower. The gram-per-watt numbers are still respectable, the tech is forgiving, and replacement bulbs are cheap. CMH is the move if you specifically care about terpene quality and UV exposure, or you want one fixture to handle both veg and flower with a white spectrum you can see your plants properly under. The Philips CDM-T Elite 315W in a dedicated CMH reflector is the reference setup.

One thing to note on comparing yields across these technologies: gram-per-watt figures depend heavily on genetics, medium, grower skill, and how well the canopy is trained. A SCROG under 400W of LED can out-yield an untrained plant under 600W of HPS. The light is one variable among many.

Electrical and fire safety

Every grow light in this guide draws serious current and all three have caused tent fires — wiring and ventilation matter as much as the fixture choice. Use an RCD-protected circuit (standard in most modern EU homes, but check — older Dutch and German wiring often isn't). Don't daisy-chain ballasts off a single cheap extension lead. HPS ballasts in particular run hot — mount them outside the tent with airflow around them. CMH fixtures need the bulb oriented correctly (horizontal vs vertical matters for bulb life and spectrum). LED drivers are generally the safest of the three but still need ventilation.

AZARIUS · Electrical and fire safety

Related products at Azarius

Azarius stocks cannabis grow lights for every tent size: LED fixtures from Mars Hydro and Lumatek, HPS ballast-and-bulb combos from Lumatek and Gavita, and CMH fixtures with Philips CDM-T bulbs — alongside the seeds from Royal Queen Seeds, Dutch Passion, Paradise Seeds, Sensi Seeds and Barney's Farm that go under them. Browse the grow shop category to order a full kit, or get individual replacement bulbs separately.

References and further reading

• Chandra, S., Lata, H., Khan, I. A., & ElSohly, M. A. (2008). Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO₂ conditions. Physiology and Molecular Biology of Plants, 14(4), 299–306.
• Rodriguez-Morrison, V., Llewellyn, D., & Zheng, Y. (2021). Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science, 12, 646020.
• Fluence Bioengineering (2023). PPFD and DLI targets for cannabis cultivation — technical application note.
• DesignLights Consortium (DLC) Horticultural Technical Requirements V3.0 (2024) — fixture efficacy testing standards.
• Trimbos Institute / Netherlands National Drug Monitor (MAPS-affiliated harm-reduction reporting) — Dutch home cultivation context and energy-use surveys.
• Beckley Foundation policy briefings on domestic cannabis cultivation in Europe.

This guide is educational information for adult home growers and does not constitute professional advice. Conditions, equipment specifications and best practice evolve — verify current manufacturer data and consult a qualified electrician for any mains wiring work.

Last updated: April 2026