LED vs HPS Grow Lights — 2026 Cost & Yield Math
LED won. Modern Samsung LM301H quantum boards beat HPS on PAR/W, run cooler, last 5× longer — and the price gap is closed. Complete comparison with full numbers.
BY ROOTLESS FARM
The thirty-second answer
LED grow lights have won. Modern quantum boards (Samsung LM301H+, Osram diodes) deliver 2.7–3.0 μmol/J vs HPS at 1.6–1.8 μmol/J — almost double the usable photons per watt. They run cooler, last 5× longer, and the price gap that justified HPS in 2018 has closed. For new builds and replacements in 2026, LED is the only reasonable choice.
Side-by-side numbers
| Factor | Modern LED (LM301H+) | HPS double-ended |
|---|---|---|
| PAR efficacy | 2.7-3.0 μmol/J | 1.6-1.8 μmol/J |
| Heat output | low | very high |
| Spectrum | full white + red supplemental | yellow-orange (no blue, no far-red) |
| Lifespan | 50,000 h | 10,000 h |
| Bulb replacement cost (5 yr) | $0 (still works) | $400-600 |
| Upfront (1m² flowering) | $350-500 | $150-200 |
| Annual electricity (600 PPFD) | $90 | $150 |
| Heat management cost | minimal | $50-100 in HVAC |
| Total 5-yr cost | $500-700 | $1100-1500 |
| Indoor safety (skin/eye burn) | safer (lower IR) | dangerous touch hazard |
| Dimming capability | smooth 0-100% | step or none |
Why LED won the efficacy race
The PAR-per-watt advantage comes from physics:
- HPS generates light by ionizing sodium vapor. Most input energy becomes heat (60%+ as IR + UV-side losses).
- LED generates light by electrons crossing a semiconductor bandgap. ~50% of input energy becomes usable photons; rest is heat.
A 600W HPS produces ~1000 μmol/s of PAR. A 400W modern LED produces the same. The LED uses 33% less electricity for the same plant-usable light.
Over 5 years at 12 hours/day, that's:
- HPS: 600W × 12h × 365 × 5 = 13,140 kWh
- LED: 400W × 12h × 365 × 5 = 8,760 kWh
- Savings: 4,380 kWh × $0.15/kWh = $657
Plus HVAC savings (less heat to remove) of another $200-400 over 5 years.
What changes if you switch from HPS to LED
AC requirement drops 30-40%
HPS dumps most of its energy as heat. Removing that heat requires AC. Switching to LED reduces both the heat load and the AC sizing.
VPD targets shift slightly
LED leaves run 1-3 °C cooler than HPS leaves (less IR). VPD targets calculated on air temperature alone may overestimate water demand. Adjust irrigation slightly downward in the first month after switching.
DLI stays the same
Plants don't care about the source — they care about photons. If your HPS delivered 600 PPFD at 30 cm and you replace with an LED delivering 600 PPFD at 30 cm, the plant sees identical DLI. Hit your target μmol with less wattage.
Spectrum control becomes possible
HPS has one spectrum (yellow-orange). LED can be dialed to crop and stage:
- Seedling/veg: 5000-6500K white-dominant with extra blue.
- Flower: 3000K warm white + 660 nm red + optional 730 nm far-red.
- Mother plants: cool white with high blue.
See light spectrum explained and photoperiod and flowering.
Where HPS might still make sense (the edge cases)
Cold winter greenhouse
HPS's heat is a feature in a cold greenhouse. The 600W of "wasted" heat keeps the air warm enough for tropical crops. LED in the same setup requires supplemental heating.
For a small commercial cold-region operation, HPS may still be cheaper net once heat-credit is factored.
Tight upfront budget
A used 600W HPS + ballast + reflector costs $80-120 on the secondhand market. An equivalent LED is $300-400 new. For a single-cycle test grow or short-term setup, used HPS is cheaper to start.
Specialized far-red supplementation
Some HPS bulbs (and most HPS systems) include high red and far-red output that benefits late-flower fruiting crops. Modern LEDs match this if you buy with far-red supplementation.
Buying recommendations for LED in 2026
Premium (~$500-700)
- HLG (Horticulture Lighting Group) — Samsung LM301H boards, MeanWell drivers.
- California Light Works SolarSystem — commercial-grade, dimmable, multi-channel spectrum.
- Gavita Pro 1700e — high-output professional fixture.
Mid-range (~$200-400)
- Spider Farmer SE/SF series — best value, decent efficacy (~2.5-2.7 µmol/J).
- Mars Hydro TS/SP series — popular, reliable.
- ViparSpectra XS series — good efficacy, dimmable.
Budget (~$100-200)
- Shop-LED 4-foot linkables for seedlings and microgreens (~$25 each).
- AC Infinity Ionboard for veg-stage lettuce/herbs.
Avoid: "blurple" LEDs and any LED without published PPF and µmol/J specs. See choosing a grow light and watts per plant.
The transition timing
If you have HPS fixtures running:
- Don't replace mid-cycle — plants adjust to spectrum shifts over 2-3 weeks of growth.
- Replace at end of current cycle — clean transition.
- Sell the HPS while still functional ($30-80 on used market).
For new builds: LED only. The break-even on switching from HPS was 2020. The premium for waiting is electricity bills.
See also
FAQ
5 entries- Q01Is HPS ever still worth it?
- For a single 1m² flowering tent on a tight upfront budget where ambient temp is below 18°C, marginally. Otherwise LED wins on every metric in 2026 — efficacy, heat, lifespan, total cost.
- Q02Do LEDs really last 50,000 hours?
- At rated drive current, yes — but most cheap fixtures run their diodes hot. Buy MeanWell-driver fixtures with under-driven diodes. Premium LEDs (Spider Farmer, Mars Hydro, Gavita Pro) generally honor the 50,000h spec.
- Q03How much do I save by switching to LED?
- 30-40% on electricity and HVAC. A 600W HPS replaced by a 400W LED (delivering the same PPFD) saves 200W × photoperiod × 365 days = $80-150/year in electricity plus cooling cost.
- Q04What spectrum should I look for in LED?
- White-LED dominant (5000K base) + supplemental red (660 nm) and optional far-red (730 nm) for flowering. Avoid old "blurple" LEDs — narrow spectrum, hard to inspect plants, less canopy penetration.
- Q05Will my old HPS plants struggle under LED?
- Not if PPFD matches. Plants don't care about the source — they care about photons. Switch lamps at the start of a cycle for cleanest transition.