LED vs HPS vs CMH for Cannabis in 2026: An Honest Comparison From a Shop That Stocks All Three

LED won most cannabis grows in 2026, but four scenarios still favor HPS or CMH. A retailer's honest three-way comparison with PPFD numbers and 2026 buying picks.

Last winter a customer drove an hour to the shop carrying a $1,800 LED bar fixture in the box and a question: why was his harvest worse than the one he got with the old 600W HPS the LED replaced? The plants slowed in week 3 of flower, the buds came out airy, and his electric bill barely moved. He had read four "LED is better than HPS" articles before buying. Not one had told him that his unheated detached garage was running 12 degrees colder without the HPS heat load, that his VPD had crashed, and that LEDs require a different feed and watering rhythm than HPS. He returned the LED and went back to the HPS for the rest of winter.

LED has won most cannabis grows in 2026. This article is about the cases where it hasn't, why almost every comparison guide online is selling you the wrong light, and how to know which technology fits your specific grow.

We sell HPS, CMH, and LED at Modern Farms. We have no contractual reason to push one technology over the others, and we've watched hundreds of customers make this decision over the past five years. The honest answer is that LED is the right choice for roughly 80 percent of growers, but four specific scenarios still favor HPS, and one specific scenario still favors CMH. The pages currently ranking on Google won't tell you any of this clearly, partly because most of them are written by people who only sell one of the three technologies.

What follows is the comparison we'd give a customer face to face, with the actual numbers (PPE, PPFD, gram-per-watt) and the cases where each technology genuinely earns its place.

The Three-Way Verdict in One Paragraph

LED for roughly 80 percent of cannabis growers, full stop. The technology is now efficient enough (PPE 2.7 µmol/J or higher in good fixtures), affordable enough (a quality 4x4 LED runs $300 to $700), and durable enough (50,000+ hour life) that it makes sense for most home grows and almost all serious commercial operations. HPS is still the right choice for four specific cases: cold-climate growers who use HPS heat as supplemental heating, large-room commercial growers where per-fixture cost matters more than long-term electricity savings, growers on extreme budgets who need a working flower light for under $150, and growers running CO2 supplementation at high room temperatures. CMH is still the right choice for one specific case: boutique terpene-focused growers in 3x3 to 4x4 footprints who care more about flavor than maximum yield. Outside those scenarios, LED wins.

The numbers behind those claims, the specific products that deliver on them, and the operational changes nobody warns you about are below.

How Cannabis Grow Lights Actually Work (PPFD, PPE, and Why Wattage Equivalence Is a Lie)

Most online comparisons of cannabis grow lights bury the technical metrics or skip them entirely. That's a problem because the metrics are the only honest way to compare three different lighting technologies. Lumens are useless for plants. Wattage is misleading. The numbers that matter are PAR, PPFD, and PPE.

PAR (Photosynthetically Active Radiation)

PAR is the range of light wavelengths plants actually use for photosynthesis: 400 to 700 nanometers. Light outside this range still costs you electricity but doesn't grow plants. The first thing to know about HPS is that it produces a lot of light outside the PAR range (mostly infrared heat). The first thing to know about LED is that it can be tuned to produce almost exclusively PAR-range light. CMH falls between the two. This is the foundational reason LED has overtaken HPS on efficiency: more of every watt becomes useful light.

PPFD (Photosynthetic Photon Flux Density)

PPFD measures how many photons of usable light actually land on a square meter of canopy per second, expressed in micromoles per square meter per second (µmol/m²/s). For cannabis, the targets are well-established: 200 to 400 PPFD for seedlings and clones, 400 to 600 for vegetative growth, and 600 to 1000 for flowering. Anything below 400 PPFD in flower wastes electricity by underfeeding the plants. Anything above 1000 PPFD without CO2 supplementation wastes electricity by exceeding what the plant can use. The sweet spot for most non-CO2 home grows is 700 to 900 PPFD at canopy in flower.

PPFD is the metric that exposes "1000W equivalent" marketing claims. A cheap LED labeled as "1000W equivalent" might draw 100 watts from the wall and produce 400 PPFD at 18 inches above canopy. A real 600W HPS produces around 800 PPFD at the same height. The "equivalence" number means nothing. PPFD at canopy is the only number that means anything.

PPE (Photosynthetic Photon Efficacy)

PPE is the efficiency rating of the fixture: how many micromoles of PAR light it produces per joule of electricity consumed. A higher PPE means more light per dollar of electricity, period. The numbers for the three technologies in 2026 are clear:

• HPS: 1.5 to 1.7 µmol/J for double-ended (DE) fixtures, 1.0 to 1.3 for older single-ended.
• CMH: 1.7 to 1.9 µmol/J for 315W fixtures, 1.9 to 2.1 for 630W.
• LED (budget): 2.0 to 2.5 µmol/J for sub-$200 fixtures.
• LED (quality): 2.7 to 3.0 µmol/J for HLG, Photontek, AC Infinity, Spider Farmer flagship products.
• LED (commercial): 3.0 to 3.4 µmol/J for top-tier Fohse, Gavita Pro, Iluminar fixtures.

This is why retailers and content shops obscure PPE numbers. A budget LED at 2.2 µmol/J is more efficient than a CMH at 1.9, but it isn't more efficient than a quality LED at 2.9. The PPE gap between cheap LEDs and quality LEDs is bigger than the PPE gap between quality LEDs and HPS. If you're shopping a $150 LED against a $400 LED, the $400 model is producing about 40 percent more light per watt. That's the math the cheap-LED marketing doesn't want you to do.

The honest gram-per-watt math

Every grow light brand makes yield claims. Most are inflated. Here's the honest 2026 math from what we see in our customers' grows:

• HPS at 1000W DE: 0.5 to 0.6 grams per watt with experienced growers and good genetics. The "1 gram per watt" HPS claim was true in optimal commercial conditions a decade ago and is repeated as folklore now. In real home grows, 0.5 g/W is the honest number.
• CMH at 315W or 630W: 0.6 to 0.8 grams per watt. CMH gets less yield per watt than HPS but the buds are denser and more terpene-rich, which means weight isn't the only metric.
• Modern LED (quality): 1.0 to 1.5 grams per watt with experienced growers. The 2 g/W claims you see in marketing materials are achievable in commercial conditions with CO2 supplementation and perfect genetics, but they're not what most home growers will see.

Anyone telling you they consistently get 2 grams per watt at home with no CO2 is either using a single cherry-picked grow or counting wet weight. Plan for 1.0 to 1.2 g/W with quality LEDs and good technique. That's still roughly twice the yield-per-watt of HPS, which is the actual reason LED won.

HPS in 2026: Still Right For These Four Cases

High-pressure sodium has been the cannabis industry's default light for thirty years. The technology is mature, the bulbs are cheap, and the spectrum (heavy in the red and orange wavelengths between 580 and 650 nanometers) is genuinely well-suited to flowering. HPS lost ground to LED because the efficiency gap got too large to ignore, but it didn't lose every battle. Four scenarios still favor HPS over LED in 2026.

Case 1: Cold-climate growers using HPS heat as supplemental room heating

This is the case the SERP refuses to discuss. A 600W HPS produces roughly 2,000 BTU of radiant heat per hour. In an unheated detached garage in Minnesota during January, that heat is not waste: it's holding the room temperature in the 70 to 80 degree range that flowering cannabis wants. Replace the HPS with a high-efficiency LED that produces almost no radiant heat, and the room temperature crashes by 10 to 15 degrees. Now you need a space heater, which costs more electricity than the HPS was using, and the dry heat from a space heater drops your relative humidity into VPD danger territory.

If you grow in a cold space and you've been told to switch to LED for "efficiency," do the heat math first. Add the wattage of the supplemental heater you'll need to the LED's draw. Compare that total to the HPS's draw. In genuinely cold spaces, HPS often wins on total electricity used. The "efficiency" advantage of LED is real but it doesn't survive the addition of heating costs.

Case 2: Large-room commercial growers where per-fixture cost matters

A commercial cannabis facility running a 5,000 square foot flower room needs roughly 50 fixtures at 1000W each. The math at this scale is brutal. A 1000W double-ended HPS fixture costs $300 to $500. A commercial-grade LED with equivalent canopy coverage costs $1,200 to $2,000. For 50 fixtures, that's a $45,000 to $75,000 upfront difference. The LED's lower electricity bill recoups the difference within roughly 3 to 4 years, but at that scale, capital availability often matters more than five-year operating costs.

This is why you still see new commercial cannabis facilities specing HPS in 2026, especially at the lower-budget end of the licensed market. The total cost of ownership favors LED. The cash flow math sometimes still favors HPS.

Case 3: Growers on extreme budget who need a working flower light for under $150

You can buy a complete 600W HPS setup (ballast, bulb, reflector hood) for $80 to $150 in 2026. There is no LED at that price point that will produce real flowering yields in a 4x4 tent. The cheapest LEDs that actually produce decent flowering yields start at around $200 to $250 (Mars Hydro TS3000, Spider Farmer SF2000), and the quality jump happens at $300 to $400. If you have $100 to spend and you're flowering cannabis in a 3x3 or 4x4 tent, HPS is genuinely your best option.

The LED-evangelism crowd will tell you to save up for a quality LED. That's not always realistic. A working HPS now is better than a quality LED in six months. We sell HPS to first-time growers on tight budgets without apology, because the alternative is them giving up before they finish their first cycle.

Case 4: Growers running CO2 supplementation in well-ventilated rooms

CO2 supplementation lets cannabis plants tolerate higher temperatures (85 to 90 degrees instead of the usual 75 to 80) and process more light per minute. Both of those favor HPS. The higher temperature ceiling means the radiant heat from HPS is no longer a problem; the higher light tolerance means the raw photon output of a 1000W HPS at the canopy can be exploited fully. Commercial CO2 grows historically ran HPS for this reason, and many still do, especially in grows over 10x10 feet where LED bar fixtures struggle to deliver sufficient PPFD at canopy across the whole footprint.

This case has narrowed in 2026 because top-tier commercial LEDs (Fohse A3i, Gavita Pro 1700e LED, Iluminar iL5) now produce enough intensity to handle CO2 grows. But for any commercial grow not buying $1,500-plus fixtures, HPS plus CO2 is still a defensible setup.

What HPS gets wrong

The criticisms of HPS are real and worth stating bluntly. The bulbs degrade fast (replace every 10,000 to 18,000 hours, sooner if you want consistent performance). The heat is a problem in confined spaces, especially small grow tents in summer. The spectrum is red-heavy, which is great for flowering and weak for vegetative growth (most HPS growers run metal halide for veg and switch to HPS for flower, which means buying two bulb types). The terpene-quality ceiling is real: side-by-side grow journals consistently report that HPS-grown cannabis has slightly less terpene complexity than CMH-grown or quality-LED-grown cannabis. And over a 5-year grow timeline, the electricity cost difference between HPS and quality LED runs into the thousands of dollars for a serious home grow.

HPS pricing reality in 2026

A complete double-ended 1000W HPS setup (Gavita-style or equivalent) costs $300 to $500. A complete 600W single-ended HPS setup (Apollo, iPower, Vivosun) costs $80 to $200. Replacement bulbs cost $20 to $60 and last roughly 12 to 18 months at full duty. Ballasts and reflector hoods are durable; expect 5 to 10 years of use from quality models.

CMH (Ceramic Metal Halide) in 2026: The Quality Niche Nobody Talks About

CMH is the technology the 2026 SERPs are trying to bury. Most articles either skip it entirely or treat it as a footnote. That's a real disservice to the grower who values terpene quality over pure yield, because CMH still produces the highest-quality cannabis flower of any technology in this comparison. The reason isn't mysterious: CMH (also called LEC, for Light Emitting Ceramic) produces the closest spectrum to natural sunlight of any artificial grow light, and it's the only technology in this comparison that emits meaningful UV-A and UV-B in its native output.

Why CMH still matters

Cannabis evolved under sunlight, which is full-spectrum white light with significant UV content. UV is what triggers the plant's defensive trichome production, which is the same biology that produces the cannabinoids and terpenes in flower. HPS doesn't emit UV. Most LEDs don't emit UV either, or they emit it through dedicated UV diodes that are expensive, fragile, and often poorly integrated. CMH emits UV as a natural part of the bulb's light output. The result: CMH-grown cannabis tends to have higher terpene density, more pronounced aroma, and a more "natural" flavor profile than cannabis grown under HPS or non-UV LED.

This isn't just retailer folklore. Side-by-side grow journals comparing CMH and LED in identical environments consistently find that CMH produces slightly less weight per watt but significantly better flavor. One commonly cited grow journal from 2020 ran a 315W CMH against a comparable LED; the LED won on weight (12 oz vs 9 oz) but the CMH won on terpene quality, with reviewers preferring the CMH-grown bud unanimously on smoke quality. Anecdote stacked on anecdote, but the anecdotes converge.

The CMH spec realities

CMH fixtures come in two dominant sizes: 315W and 630W (which is essentially two 315W bulbs in one fixture). The 315W is the size most home growers consider; it covers a 3x3 footprint at full intensity or a 4x4 footprint at reduced intensity. The 630W covers a 4x4 to 5x5 footprint and is used in slightly larger home grows or small commercial setups. Both come in two color temperatures: 3100K (warmer, better for flowering) and 4200K (cooler, better for vegetative growth). Many growers buy both and swap bulbs at the veg-to-flower transition, which is annoying but produces excellent results.

CMH efficiency runs 1.7 to 2.1 µmol/J, which is better than HPS but well below quality LED. The bulbs cost $80 to $130 and last about 10,000 hours of useful life, though spectrum degradation starts noticeably around 7,000 hours, which is roughly two years of daily use. Fixtures cost $300 to $700 for 315W complete setups (Sun System, Phantom, Iluminar) and $700 to $1,200 for 630W double-bulb fixtures.

Where CMH wins

CMH is the right choice for one specific use case: boutique terpene-focused growers in 3x3 to 4x4 footprints who care more about flavor than maximum yield. This includes solo home growers who care about flavor, small breeders running phenotype hunts where flavor expression matters, and quality-focused dispensary suppliers in jurisdictions where flavor and terpene profile drive price more than weight. We sell CMH to perhaps 5 percent of our lighting customers. Almost all of them have run LED before, found the flavor lacking, and switched on purpose.

If you sampled bud from a CMH grow and a quality-LED grow side by side from the same genetics, most experienced smokers would pick the CMH on flavor. That's the honest sentence nobody on page one is saying.

What CMH gets wrong

CMH bulbs degrade faster than the spec sheets imply. The "10,000 hour" rating means the bulb still produces light at 10,000 hours, not that it produces useful spectrum for cannabis. Real-world spectrum degradation starts at 6,000 to 7,000 hours, and by 8,000 hours most CMH bulbs are visibly less effective at driving flowering. Replace your CMH bulbs every 18 to 24 months at full duty, regardless of what the manufacturer says.

The fixture selection in 2026 is shrinking. As LED took over the market, CMH manufacturers consolidated. Sun System (the dominant CMH brand) is still producing fixtures, as are Phantom and Iluminar. But you'll see fewer new CMH models released year over year, and some smaller brands have exited the category. Buying CMH in 2026 means buying mature, proven products rather than cutting-edge technology, which is fine for most growers but worth knowing.

CMH is weak for large rooms. A 630W CMH fixture covers maybe a 4x4 to 5x5 footprint at full intensity. To cover a 10x10 commercial flower room with CMH would require 4 to 6 fixtures at $800 to $1,200 each, plus replacement bulbs every 18 months. The economics don't work above the home-grow scale. CMH is for tents, not warehouses.

CMH pricing reality in 2026

A complete 315W CMH setup (fixture, ballast, bulb, reflector) costs $300 to $700. A 630W setup costs $700 to $1,200. Replacement bulbs cost $80 to $130. Plan to replace bulbs every 18 to 24 months. The total 5-year cost of ownership for a single 315W CMH is roughly $700 to $1,000 including bulb replacements and electricity.

LED in 2026: Why It Won and Where the Hype Is Still Wrong

LED won the cannabis lighting market because the technology genuinely is better for the average use case. Modern LED fixtures from quality brands deliver PPE of 2.7 to 3.0 µmol/J, run cool enough to mount inches above the canopy, last 50,000+ hours without bulb replacement, dim across the full 0 to 100 percent range, and offer spectrum tuning across vegetative and flowering phases. Compared to a 600W HPS that runs hot, draws 660 watts at the wall, produces maybe 1.5 µmol/J of useful light, and needs bulb replacements every 12 to 18 months, the value proposition is clear.

That doesn't mean every LED claim you read online is true. Three pieces of LED hype are still actively misleading buyers in 2026.

The LED hype that's still wrong

"1000W equivalent" wattage marketing. Cheap LEDs are still labeled "1000W equivalent" while drawing 100 to 150 watts from the wall. The "equivalence" comparison is to a hypothetical inefficient bulb and means nothing about actual photon output. Ignore wattage equivalence claims entirely. Look at actual wall draw (in watts), PPE (in µmol/J), and PPFD at canopy (in µmol/m²/s). Anyone selling you a light by referring to "wattage equivalent" is hiding the real metrics.

"2 grams per watt" yield claims. Yes, top-tier commercial LED setups under perfect conditions with CO2 supplementation can produce 2 g/W. No, your home grow will not. Plan for 1.0 to 1.2 g/W with quality LEDs and good technique. The 2 g/W marketing claim shows up on every LED product page and is achievable in maybe 5 percent of grows. Treat it as the exception, not the target.

"UV is essential for cannabis." This claim has gotten louder as LED brands try to differentiate themselves with UV-A and UV-B add-on diodes. The truth: UV is helpful for terpene and trichome development, but it's not essential and the implementation matters enormously. Cheap UV diodes burn out faster than the rest of the LED, can damage plant tissue if poorly implemented, and often add $100 to $200 to fixture cost. Unless you're growing for terpene quality at a level where the $200 matters, skip UV-supplemented LEDs and run a CMH instead if UV is what you actually want.

The honest 2026 LED landscape

Bar-style fixtures dominate quality LED in 2026. The design (multiple thin LED bars spread across the footprint instead of one central panel) gives you more uniform PPFD across the canopy, better heat dissipation through passive cooling, and fewer hotspots. Quantum boards (single-panel designs) still work for 2x2 and small 2x4 grows where uniform coverage is easier to achieve. COB (Chip-on-Board) fixtures, which were popular 2018 to 2022, are essentially obsolete in 2026 because the efficiency gap with bar fixtures got too large.

The brands that actually deliver in 2026: HLG (Horticulture Lighting Group) for hobby and prosumer fixtures with strong PPE and clean engineering. Photontek for premium bar lights with Osram diodes. AC Infinity for the prosumer market with the IONFRAME EVO series, which has aggressive PPE numbers and full app control. Spider Farmer at the budget end, with surprisingly capable fixtures (SF2000, G6000, G8600) that punch above their price. Mars Hydro for ultra-budget builds, with the TS series being functional if not premium. Fohse, Gavita Pro, and Iluminar at the commercial tier.

LED pricing reality in 2026

• 2x2 tent: $100 to $200 for a quality fixture (Spider Farmer SF1000, Mars Hydro TS1000, ViparSpectra XS1500 Pro).
• 2x4 tent: $200 to $400 for a quality fixture (Spider Farmer G4500, AC Infinity IONFRAME EVO3, HLG 350R).
• 4x4 tent: $300 to $700 for a quality fixture (HLG 600 Diablo, Photontek X600, AC Infinity IONFRAME EVO6, Spider Farmer G6000).
• 5x5 tent: $500 to $1,000 for a quality fixture (Photontek X800, Spider Farmer G8600, Mammoth Lighting Nova 8 Bar).
• Commercial: $1,000 to $2,000+ per fixture (Fohse A3i, Gavita Pro 1700e LED, Iluminar iL5).

Spend less than the budget bracket for your tent size and you'll get poor coverage, poor PPE, or both. Spend more than the budget bracket and you're paying for marginal improvements that don't pay back in yield. The sweet spot for most home growers is the middle of each bracket from a quality brand.

The Real Cost Comparison: Five-Year Total Cost of Ownership

Forum threads love to argue about price, but they rarely show the math past the upfront purchase. Here's the five-year total cost of ownership for a 4x4 cannabis flower tent running four cycles per year (twelve weeks each, 18 hours per day in veg, 12 hours per day in flower), at $0.16 per kWh average US residential electricity. Twenty grow cycles total. The numbers will surprise growers who only compare upfront sticker prices.

HPS: 600W single-ended setup

• Initial fixture, ballast, reflector: $150
• Bulb replacements (4 over 5 years at $35 each): $140
• Electricity (660W actual draw, average 14 hours per day, 5 years): $2,700
• Supplemental ventilation (booster fan to handle heat load): $80

Five-year total: roughly $3,070.

CMH: 315W fixture

• Initial fixture, ballast, reflector, two bulbs (3100K + 4200K): $500
• Bulb replacements (4 over 5 years at $100 each): $400
• Electricity (340W actual draw, average 14 hours per day, 5 years): $1,390
• Supplemental ventilation: $40

Five-year total: roughly $2,330.

Quality LED: 600W bar fixture (HLG 600 Diablo or equivalent)

• Initial fixture: $700
• Bulb replacements (none, 50,000+ hour rated): $0
• Electricity (630W actual draw, average 14 hours per day, 5 years): $2,580
• Supplemental ventilation (minimal, less heat): $0

Five-year total: roughly $3,280.

What this math actually shows

The five-year cost difference between HPS, CMH, and quality LED is much smaller than the upfront cost difference suggests. CMH actually wins on five-year cost in this scenario because the lower wattage produces meaningful electricity savings over time, and the upfront premium is moderate. LED's electricity efficiency advantage exists but doesn't dominate the math the way LED marketing implies.

The numbers shift in three real-world scenarios. In commercial settings running 24/7, LED's electricity efficiency compounds dramatically and LED wins by thousands of dollars per fixture over five years. In high-electricity-cost regions (California, Hawaii, parts of the Northeast at $0.30+ per kWh), LED also pulls ahead because the electricity savings scale with rate. In cold climates where HPS heat replaces space heating, HPS pulls ahead because you're not paying separately for room heat.

The takeaway: don't buy LED for the electricity savings. Buy LED for the durability, the heat management, the dimming control, and the spectrum quality. The electricity savings are real but they're not the dominant factor for most home grows.

The Decision Framework: How to Know Which One You Should Buy

The technology comparison above is necessary background. The decision is what actually matters. Here's the framework we use at the counter, organized by the situation the grower describes.

"First-time grower, 2x2 or 2x4 tent, single setup"

Buy: a modern LED quantum board or compact bar fixture, $150 to $300. The Spider Farmer SF1000 ($100), Mars Hydro TS1000 ($120), or ViparSpectra XS1500 Pro ($140) for a 2x2; the Spider Farmer SF2000 ($210) or AC Infinity IONFRAME EVO3 ($300) for a 2x4. LED is unambiguously the right choice at this scale because heat dissipation in small tents is a real problem with HPS, the upfront-cost gap with HPS is small at this footprint, and you'll grow into the LED's longer lifespan. There is no honest case for HPS in a 2x2 tent.

"Hobby grower, 4x4 single tent, quality matters more than yield"

Buy: a CMH 315W fixture or a premium UV-supplemented LED. The Sun System LEC 315 ($350 to $500) or the Phantom Dual 315 ($450 to $600) are the standard CMH picks. If you'd rather stay LED, the HLG 600 Diablo ($700) with its V2 design is the closest LED match for terpene quality. If your priority is the densest, most flavorful flower from a single strain at a time, CMH is still genuinely the best choice in 2026, regardless of what most articles tell you.

"Hobby grower, 4x4 single tent, yield matters more than anything"

Buy: a premium LED bar fixture, $500 to $800. The HLG 600 Diablo ($700), Photontek X600 ($650), AC Infinity IONFRAME EVO6 ($600), or Spider Farmer G6000 ($550) are the four serious options. All four deliver PPE in the 2.7 to 2.9 µmol/J range, even PPFD coverage across the 4x4 footprint, and full dimming control. The differences between them are small enough that buying the cheapest of the four is rarely a mistake. Spider Farmer G6000 is the best value pick for first-time LED buyers; Photontek X600 has the best PPE for the watt; HLG and AC Infinity have stronger US support and warranty.

"Commercial-leaning grower running 5x5 or larger"

Buy: LED bar arrays, no exceptions. The economics at this scale are not even close. Photontek X800 ($900), Mammoth Lighting Nova 8 Bar ($800 to $1,000), or Spider Farmer G8600 ($750) for 5x5; multiple Fohse A3i ($1,800 each), Gavita Pro 1700e LED ($1,400), or Iluminar iL5 fixtures for serious commercial. Quality LED is the only technology that delivers the PPFD uniformity needed to flower a large room well. CMH covers too small a footprint per fixture; HPS produces too much heat to manage at scale unless you're running CO2 with industrial HVAC.

"Cold-climate grower in unheated space, winter-only or year-round"

Buy: HPS, or a hybrid HPS+LED setup. A 600W or 1000W HPS in winter; switch to or supplement with LED in summer if heat becomes the problem instead of cold. We have customers in Vermont, Montana, and northern Michigan running HPS year-round in unheated outbuildings because the heat is part of the system. The "switch to LED for efficiency" advice doesn't survive the addition of supplemental heating costs in genuinely cold spaces. Calculate total electricity (light + heater) before assuming LED wins on efficiency.

"Boutique terpene-focused breeder, single-strain testing"

Buy: CMH 315W. Sun System LEC 315, with both the 3100K and 4200K bulbs so you can swap for veg and flower. CMH gives you the closest-to-natural-sunlight spectrum, native UV output, and the terpene quality that breeders running phenotype hunts care about. Yield is secondary at this use case; quality of expression is everything. Plan to replace bulbs every 18 months at full duty.

"Beginner on tight budget, refuses to spend over $200"

Buy: HPS, no exceptions. A complete 600W HPS setup (ballast, bulb, reflector hood) costs $80 to $150 at any major retailer. A working LED that produces real flowering yields starts at $200 and the quality jumps at $300. If you have $100 to $150 to spend and you want to flower cannabis in a 4x4 tent, HPS is the answer. The LED-evangelism crowd will tell you to save up. That's not always realistic, and a working HPS now beats a quality LED in six months. Plan to replace the HPS bulb in 12 to 18 months ($30) and upgrade to LED when budget allows.

"Grower running CO2 supplementation"

Buy: 1000W double-ended HPS for budget builds, premium LED for premium builds. CO2 lets cannabis tolerate higher temperatures and process more light, both of which favor HPS at the budget end. A 1000W DE HPS (Gavita-style, $400 to $600) plus CO2 still beats a $600 LED in a CO2-supplemented room. At the premium end, a top-tier LED like the Fohse A3i ($1,800) or Gavita Pro 1700e LED ($1,400) produces enough intensity to fully exploit CO2 with much better PPE. For mid-range CO2 grows, HPS is still defensible.

The Operational Changes Nobody Warns You About

This is the section nobody else writes, and it's the reason that customer mentioned at the start of this article got worse results from his $1,800 LED. Switching from HPS to LED is not a one-for-one swap. The light technology change cascades into VPD changes, feed EC changes, watering frequency changes, and canopy distance changes. Ignore any of them and your grow gets worse, not better.

VPD shifts

VPD (Vapor Pressure Deficit) is the difference between the moisture in the air and the maximum moisture the air could hold at a given temperature. It drives transpiration, which drives nutrient uptake. HPS-grown plants prefer VPD in the 1.0 to 1.2 kPa range during flowering because the radiant heat from HPS keeps leaf temperature several degrees above ambient air temperature, which raises the effective VPD at the leaf surface even when the room VPD reading is lower. LEDs produce almost no radiant heat, so leaf temperature stays close to ambient, which means you need to dial room VPD higher (1.2 to 1.5 kPa during flower) to get the same transpiration response.

If you switch from HPS to LED and don't adjust VPD, your plants will transpire less, drink less, eat less, and grow more slowly. This is the most common complaint we hear from customers who switched lights and saw worse results.

Feed EC adjustments

Lower transpiration under LED means slower water uptake, which means EC creep in your reservoir gets worse. The plants are taking up water at a slower rate but the salts in the reservoir are still concentrating from evaporation. If you used to refresh your nutrient reservoir every 7 days under HPS, plan to refresh every 5 days under LED, or run a slightly lower starting EC (1.4 instead of 1.6 in flower) to give yourself more headroom before the EC climbs into burn territory.

Plants under LED also tend to need slightly less calcium and magnesium because the lower transpiration rate reduces the calcium-pump dynamics in the leaves. CalMag-heavy growers who switch from HPS to LED often find they're over-supplementing for the first few cycles. Cut your CalMag dose by 25 percent on the first LED cycle and adjust based on what the leaves tell you.

Watering frequency changes

Plants under LED transpire 15 to 25 percent less than plants under HPS at the same canopy PPFD. That means your watering frequency drops. A grower who waters every two days in coco under HPS will likely need to water every three to four days under LED. Overwatering is the single most common rookie mistake when switching from HPS to LED. The plants look thirsty (it's flower week 3, you're used to dry pots) but the medium is still wet because evaporation has slowed. Stick a finger in the medium, lift the pot to feel the weight, or use a moisture meter. Don't water on schedule when you switch lights; water when the plants actually need it.

Canopy distance differences

HPS needs to hang 24 to 36 inches above the canopy because of the heat. CMH can run 18 to 24 inches. Quality LED can run 12 to 18 inches. This matters when you're planning your tent height. A 7-foot grow tent is comfortable for HPS; a 5-foot tent is fine for LED. If you're upgrading your tent and your light at the same time, factor this in. LEDs let you grow taller plants in shorter tents because you reclaim the headspace the HPS needed for heat dissipation.

The flip side: LED's closer canopy distance means PPFD changes faster with small height adjustments. Move an HPS 2 inches closer and PPFD goes up maybe 10 percent. Move an LED 2 inches closer and PPFD can go up 25 percent or more. The intensity sensitivity is real. If you're not running a PPFD meter, hang your LED at the manufacturer's recommended distance and don't move it without good reason. If you are running a PPFD meter, dial in the height for your target PPFD and adjust as plants grow.

Spectrum and stretch

HPS's red-heavy spectrum encourages stretch (vertical growth) during early flower. LED's more balanced spectrum produces less stretch. Growers switching from HPS to LED often find their plants don't stretch as much in the first two weeks of flower as they're used to, which means the canopy is shorter than expected. Two responses: either compensate by training plants taller during late veg, or accept the shorter canopy and adjust expectations. Neither is wrong; both require planning.

2026 Specific Product Picks Across All Three Technologies

This is what we'd actually recommend if you walked in today and asked us to spec your room. Prices are 2026 retail averages and may differ at your local shop.

HPS picks

Premium 1000W double-ended: Gavita Pro 1000e DE Complete Fixture ($450 to $600). The benchmark commercial HPS in 2026. PPE around 1.7 µmol/J. Includes electronic ballast, reflector, and bulb. Used by serious commercial growers running CO2.

Mid-range 600W or 1000W: Sun System LEC 1000W or iPower Greenhouse Grow Light Kit ($150 to $300). Reliable, well-built, no surprises. Good for hobby growers who want HPS at a fair price.

Budget 600W setup: Vivosun 600W HPS Grow Light Kit or Apollo Horticulture 600W ($80 to $130). Budget-tier construction, but functional. The right choice for the under-$150 budget grower.

CMH picks

315W single-ended: Sun System LEC 315 ($350 to $500). The standard CMH fixture for a single 3x3 or 4x4 tent. Sun System is the dominant CMH brand and the bulb supply is reliable. Buy with both 3100K (flower) and 4200K (veg) bulbs.

315W premium: Phantom Dual 315 PHANTOM CMh ($450 to $600). Higher build quality, better thermal management, dimming control. Worth the upgrade if you're committing to CMH long-term.

630W double-bulb: Sun System LEC 630 or Iluminar 630W CMH ($700 to $1,200). For 4x4 to 5x5 tents at full intensity. Two 315W bulbs in one fixture.

LED picks by tent size

2x2 tent ($100 to $200): Spider Farmer SF1000 ($100), Mars Hydro TS1000 ($120), or ViparSpectra XS1500 Pro ($140). The SF1000 is the best value pick for first-time growers. The XS1500 Pro is the best balanced pick if you want slightly more intensity.

2x4 tent ($200 to $400): Spider Farmer SF2000 ($210), Spider Farmer G4500 ($380), or AC Infinity IONFRAME EVO3 ($300). The G4500 is the best in this bracket for serious flowering. The IONFRAME EVO3 wins if you value app control and integration with AC Infinity tent automation.

4x4 tent ($300 to $700): Spider Farmer G6000 ($550), Photontek X600 ($650), HLG 600 Diablo ($700), or AC Infinity IONFRAME EVO6 ($600). All four deliver PPE in the 2.7 to 2.9 µmol/J range. Pick by budget and ecosystem preference. The G6000 is the best value. The Photontek X600 has the best PPE per dollar. The HLG 600 Diablo has the strongest US-based service. The IONFRAME EVO6 wins for app integration.

5x5 tent ($500 to $1,000): Spider Farmer G8600 ($750), Photontek X800 ($900), or Mammoth Lighting Nova 8 Bar ($800 to $1,000). At this footprint, bar-style is essentially the only option. Single-board fixtures don't deliver uniform coverage at 5x5.

Commercial ($1,000 to $2,000+ per fixture): Fohse A3i ($1,800), Gavita Pro 1700e LED ($1,400), or Iluminar iL5 ($1,500). All three deliver PPE above 3.0 µmol/J and are built for 24/7 commercial duty cycles. The Fohse A3i is the boutique commercial pick; Gavita and Iluminar are the volume commercial picks.

Veg-specific lights (separate veg room or nursery)

If you run a separate veg room or propagation nursery, dedicated veg-spectrum LEDs cover more canopy per watt than dimmed flower lights. The HLG 100 V2 (4000K) at $130 covers a 2x4 veg footprint efficiently. The Spider Farmer SF1000D at $90 works for clones and seedlings in a 2x2.

Under-canopy lighting (advanced technique)

Under-canopy LEDs (red-heavy bar lights mounted below the canopy to light lower bud sites) are now standard in serious commercial grows and increasingly used in hobby grows. The Grower's Choice 120W Under Canopy ($200) and the ION LED 135W ($280) are the two main options. Adds 10 to 15 percent yield in tall canopies if installed correctly. Skip this for first-time grows; consider it after you've optimized the main lighting.

What We'd Tell You at the Counter

The honest summary, framed the way we'd say it to a customer face to face.

If you're new to indoor growing and you want a single recommendation that fits 80 percent of cases, buy a quality LED in the right size for your tent. Spider Farmer G6000 for a 4x4, Spider Farmer SF1000 for a 2x2. Add a basic PPFD meter (the Apogee MQ-50 at $290 is the budget standard, the MQ-500 at $470 is the better tool). Skip the additives, skip the UV add-ons, skip the under-canopy lighting until you've finished three cycles successfully. The boring setup wins.

If you're serious about flavor and you grow one or two strains at a time, run a CMH 315W. The yield will be lower than with a quality LED. The flower will be better. We sell CMH to a small minority of customers and almost all of them have run LED first and chosen CMH on purpose, knowing the tradeoff.

If you grow in an unheated space in a cold climate, run HPS. The advice you've read elsewhere about LED efficiency assumes a heated room. Your room isn't heated. The HPS heat is part of the system. Don't fight it.

If you're scaling up to commercial, run quality LED bar arrays from day one. The economics are not even close once you're past two or three fixtures.

And whatever you buy, buy a PPFD meter. The single biggest source of underperformance in cannabis grows is growers who don't measure light intensity at the canopy. A meter costs $290 and tells you the truth about your light fixture, your hanging height, and your canopy management. Without it, you're guessing.

Modern Farms stocks HPS, CMH, and LED grow lights from the brands mentioned in this article, plus PPFD meters, ballasts, replacement bulbs, and the climate control gear (fans, filters, controllers) that supports each lighting technology. We sell all three because all three still have legitimate use cases. If you have questions about your specific grow space, climate, or budget, we're happy to help in person or by phone. We don't upsell.

"This article is for informational and educational purposes only. Cannabis cultivation laws vary by state and locality. Grow only in accordance with the laws that apply to you, and where required, only as a licensed grower. Modern Farms sells equipment and supplies and does not provide legal advice."