For 40 years, High Pressure Sodium (HPS) was the workhorse of commercial horticultural lighting. Then Ceramic Metal Halide (CMH) gave HPS its first serious challenger. Then LED arrived and changed the math entirely. As of 2026, all three are still sold and still installed — but each makes sense in different situations.
This guide compares them honestly: where each technology wins, where each falls short, and how to choose between them based on your specific room, crop, and budget.
The Three Technologies at a Glance
| HPS | CMH / LEC | LED | |
|---|---|---|---|
| Typical efficacy (2026) | 1.7 μmol/J | 1.9 μmol/J | 2.5 – 3.2 μmol/J |
| Spectrum | Yellow-red-heavy, deficient in blue | Full-spectrum, UV-rich | Engineered — anything from veg-blue to flower-red to full spectrum |
| Heat output | Very high (radiant + IR) | High | Lower (mostly conductive) |
| Bulb/diode life | 10,000-12,000 hrs | 15,000-20,000 hrs | 50,000+ hrs (L70) |
| Upfront cost per μmol/s | Lowest | Mid | Highest (but falling) |
| Operating cost (electricity + bulbs) | Highest | Mid | Lowest |
| Dimmability | Limited | Limited | Native, 0-100% |
| Best for | Tight budget, supplemental greenhouse | Vegetative growth, UV-loving crops | Most use cases, especially sealed rooms |
HPS — The Legacy Standard
What it is: High Pressure Sodium. Gas discharge bulbs filled with sodium vapor. The light is produced by an electrical arc passing through ionized sodium gas, which emits a strong yellow-orange wavelength signature.
Where it still wins:
- Greenhouse supplemental lighting. Greenhouses already have sunlight providing the full spectrum and the cool-temperature wavelengths. HPS fills in the yellow-red end that drives flowering, and growers don’t have to pay for spectral wavelengths the sun already supplies.
- Lowest upfront cost. A 1,000 W double-ended HPS fixture costs a fraction of a comparable LED. For growers expanding fast and managing capex tightly, HPS still wins on day-one cost.
- Heat as a feature, not a bug. In a cold climate or a winter greenhouse, the heat from HPS reduces or eliminates the need for supplemental heating. LED operators in cold climates often have to add heaters — that’s a real cost LED is shifting onto them.
Where it loses:
- Lowest efficacy of the three. You’re paying for 60-70% of input watts as heat, not light. Over a 5-year run, the electricity cost difference vs. LED dwarfs the upfront price gap.
- Spectrum is poor for vegetative growth — blue-deficient. Most HPS growers run a separate metal halide bulb during veg.
- Bulbs degrade quickly. Even properly maintained, an HPS bulb loses ~15% of PPF in the first year. Most commercial growers replace bulbs every 9-12 months.
- Heat is also a liability in sealed rooms — you need bigger HVAC to remove it.
CMH / LEC — The Spectrum Specialist
What it is: Ceramic Metal Halide (sometimes branded LEC, Light Emitting Ceramic). A metal halide variant that uses a ceramic arc tube instead of quartz. Produces a much broader spectrum than HPS, including significant UV-A and UV-B output.
Where it still wins:
- Vegetative growth. The blue-rich, broad spectrum of CMH is excellent for veg. Tight internode spacing, robust stem growth, strong leaf development.
- UV exposure for terpene/cannabinoid production. Some research suggests UV-B exposure during late flower increases secondary metabolite production in cannabis. CMH delivers this natively; most LED fixtures require add-on UV bars.
- Color rendering. CMH’s full-spectrum white light is excellent for visual inspection — you can see actual plant color, which matters for diagnosing deficiencies and disease.
- Lower heat than HPS. A 315 W or 630 W CMH runs cooler than a comparable 600 W or 1,000 W HPS.
Where it loses:
- Efficacy is between HPS and LED — better than HPS, but not as good as modern LED.
- UV-B exposure requires safety protocols (UV-blocking glasses, no skin exposure during operation).
- Bulb replacement costs are still a factor.
- The form factor is awkward for some grow tents — bulbs are vertical, requiring more vertical headroom.
LED — The Modern Default
What it is: Solid-state lighting using semiconductor diodes. Each diode emits a specific wavelength; the fixture combines many diodes to produce a target spectrum. Modern horticultural LEDs use binned diodes from manufacturers like Samsung (LM301H, LM301B), Osram, and Bridgelux.
Where it wins:
- Efficacy. Premium LED fixtures hit 2.7-3.2 μmol/J — nearly 2x the photon output per watt of HPS. Over a 5-10 year fixture life, this is a large operational cost difference.
- Spectrum engineering. Manufacturers can tune spectrum to the crop and growth stage. Quantum Board / quantum panel LEDs deliver well-balanced full spectrum. Dedicated veg or flower spectrums are available.
- Dimming. Native 0-100% dimming on most fixtures. This matters for managing crop intensity during transitions (seedling to veg, veg to flower) without changing fixtures.
- Heat profile. LED heat is conductive (carried away by heatsinks), not radiant. Plants receive less infrared, which means cooler canopy temperatures at the same PPFD — beneficial in sealed environments.
- Lifespan. Properly designed LED fixtures hold up to 50,000+ hours before reaching L70 (70% of original output). That’s 11+ years at 12-hour photoperiods.
- Form factor. Bar lights, panel lights, hybrid HPS-replacements — many shapes for different rooms.
Where it loses:
- Upfront cost. Premium LED still costs 2-3x what an HPS setup costs at equivalent PPF. The math works on a 3-5 year horizon, but it’s a real capital expense.
- Quality varies wildly. The LED space has many cheap fixtures using budget diodes (Epistar, no-name), poor drivers, and inadequate heatsinks. Efficacy figures from these brands are often “diode level” not “fixture level” — actual delivered output can be 30-40% lower than advertised.
- Heat as a missing benefit. Cold-climate growers may need supplemental heating that HPS operators don’t.
- UV/IR add-ons. Most LEDs don’t include UV-B; if you want it, you’re buying separate UV bars.
The premium-vs-budget LED problem: A $200 1,000 W “LED grow light” on a marketplace and a $1,500 commercial LED fixture both have “LED” on the label. They’re not the same. The premium fixture is using current-bin Samsung diodes, a 94%+ efficient Mean Well driver, and substantial aluminum heatsinking. The budget fixture is using older or downgraded diodes, a cheap driver, and minimal heatsink. The premium fixture delivers what it advertises; the budget one usually doesn’t.
How to Choose
The right answer depends on three factors: room type, crop, and time horizon.
If you’re a greenhouse grower with existing sunlight: HPS for supplemental lighting still pencils out for many operations. LED becomes more compelling when electricity rates are above ~$0.10/kWh.
If you’re a sealed indoor grower doing high-value crops: LED, almost always. The lower heat load, better efficacy, and spectrum control compound advantages in a sealed environment.
If you grow leafy greens, herbs, or microgreens: LED. The lower PPFD targets are perfectly served by modern LED, and the energy savings vs. HPS at these PPFD levels are significant.
If you want UV exposure for terpene/cannabinoid production: CMH for flower, or LED with dedicated UV bars.
If you’re capital-constrained: Used HPS rigs are still abundant on the resale market. Buy proven equipment from a closing operation rather than cheap unknown LED.
If electricity is expensive and you’re planning a 5+ year operation: LED. The math will work over the long term.
Bottom Line
LED is the default in 2026 for new commercial sealed-room operations. HPS retains a foothold in greenhouse supplemental lighting and tight-budget operations. CMH occupies a niche where its broad spectrum and UV output match the crop need.
Don’t pick a technology and then shop within it. Pick the metric that matters (PPF, efficacy, DLI you need to deliver) and let the technology fall out of that.
Browse the directory by light type to see filtered options across all three technologies.