LED vs CMH vs HPS: Which Grow Light is Right?

Why Your Choice of Grow Light Matters More Than You Think

Light is food for your plants. Get it wrong and everything else you do (nutrients, pH, airflow) gets held back. Get it right and your plants grow faster, produce more, and stay healthier from start to finish.

We’ve been selling and testing grow lights at our Sunshine Coast shop since 1990. Back then, HPS was about the only real option. Now you’ve got LED, CMH (also called LEC), and HPS all fighting for your attention. Each one has genuine strengths. Each one has real downsides. None of them is “the best” for every grower in every situation.

This guide breaks down all three so you can pick the right light for your space, your budget, and the way you actually grow. No hype. Just what we’ve learned over 35 years of helping people set up grow rooms on the Sunshine Coast and across Australia.

If you’re brand new to indoor growing, read our beginner’s guide to hydroponics first. It’ll give you the full picture before you get into lighting details.

HPS (High Pressure Sodium)

What It Is

HPS lights use a gas-filled tube that produces a warm, orange-yellow glow when electricity passes through it. They’ve been the standard for indoor growing since the 1970s. If you’ve ever walked past an older street light with that warm amber colour, that’s HPS technology.

A typical HPS setup has three parts: the bulb, a reflector (hood), and a ballast that regulates power. You’ll usually see them in 250W, 400W, 600W, and 1000W sizes.

Pros

• Proven track record. Decades of results. Growers have dialled in HPS growing to an exact science.
• Lowest upfront cost. A quality 600W HPS kit costs significantly less than a comparable LED.
• Excellent flower production. That warm orange-red spectrum is exactly what plants want during bloom. Heavy flowers, dense fruit.
• Simple to use. Plug it in, hang it up, set your timer. Not much to configure.
• Easy to find replacement bulbs. Available everywhere, including our shop in Kunda Park.

Cons

• Runs hot. A 600W HPS puts out serious heat. In Queensland summers, that means bigger fans, more ducting, and higher cooling costs.
• Higher power bills. HPS draws more electricity per unit of usable light than LED or CMH. Over a year, the difference adds up.
• Bulb replacement. HPS bulbs lose intensity over time. Plan to swap them every 9 to 12 months for best results.
• Limited spectrum. Mostly red/orange. Plants in veg stage prefer more blue light, so some growers add a metal halide (MH) bulb for veg and switch to HPS for bloom.
• Shorter lifespan. Bulbs last around 10,000 to 15,000 hours before they need replacing.

Best For

Growers on a tight startup budget who want proven bloom performance. Also a solid pick if you’re in a cooler climate where the extra heat actually helps keep your grow room warm during winter.

CMH / LEC (Ceramic Metal Halide)

What It Is

CMH stands for Ceramic Metal Halide. You’ll also see it called LEC (Light Emitting Ceramic). Same technology, different brand name.

CMH uses a ceramic arc tube instead of the quartz tube found in regular metal halide or HPS bulbs. That ceramic tube handles higher temperatures, which lets the bulb produce a wider, more natural light spectrum. The light looks closer to sunlight than either HPS or standard MH.

They come in 315W and 630W (double-ended) sizes. The 315W is the most popular for hobby growers.

Pros

• Full spectrum. CMH produces light across a wide range, including UV-A and UV-B. This gives plants a more complete light diet without needing separate veg and bloom bulbs.
• Better efficiency than HPS. A 315W CMH produces results similar to a 400W to 600W HPS while using less power.
• Less heat than HPS. Still warm, but noticeably cooler watt-for-watt. Easier to manage in a tent, especially on the Sunshine Coast where ambient temps are already high.
• Great colour rendering. The light looks natural and white, which makes it easy to spot pests, deficiencies, or discolouration on your plants. No more guessing under orange HPS glow.
• Longer bulb life than HPS. CMH bulbs hold their intensity well for around 20,000 hours.
• UV output. The small amount of UV that CMH produces can increase essential oil production and improve plant quality.

Cons

• Higher upfront cost than HPS. A 315W CMH fixture costs more than an equivalent HPS kit, though less than most LEDs.
• Limited wattage options. You’re mostly looking at 315W or 630W. No 1000W option like HPS.
• Still produces heat. Less than HPS, but more than LED. You’ll still need good ventilation.
• Bulb replacement still needed. Not as often as HPS, but CMH bulbs do degrade over time.
• UV safety. That UV output is great for plants but you should avoid staring directly at a CMH bulb. Use UV-rated glasses if you spend time in the grow room with them on.

Best For

Growers who want better light quality than HPS without the high price of LED. Great middle-ground option. Particularly good if you value being able to see your plants in natural-looking light.

LED (Light Emitting Diode)

What It Is

LED grow lights use semiconductor chips to produce light. Modern full-spectrum LED panels use a mix of diodes tuned to different wavelengths, giving plants exactly the light colours they need. The technology has improved massively in the last five to eight years. The cheap purple/blurple panels from 2015 are nothing like today’s Samsung-diode, full-spectrum bars.

LEDs come in all shapes: quantum boards, light bars, COB (chip on board), and bar-style fixtures. Wattages range from 100W for small tents to 800W+ for large grow rooms.

Pros

• Most energy efficient. LEDs convert more electricity into usable plant light than HPS or CMH. That means lower power bills, month after month. Over a two to three year period, the energy savings often pay for the higher upfront cost.
• Least heat output. LEDs run significantly cooler than HPS and CMH. In Queensland, this is a big deal. Less heat means smaller fans, less ducting, lower cooling costs, and happier plants in summer.
• Long lifespan. Quality LEDs last 50,000 to 100,000 hours. No bulb swaps. You buy it once and it keeps going for years.
• Full spectrum options. Top-tier LEDs offer tuneable spectrum with separate channels for veg, bloom, and UV/IR. One light covers every stage of growth.
• Dimmable. Most quality LEDs let you dial down the intensity for seedlings and ramp up for bloom. HPS and CMH are typically full power or off.
• Even light spread. Bar-style LEDs distribute light more evenly across your canopy than a single-point HPS or CMH reflector.
• Less frequent replacements. No bulbs to swap. No reflectors to clean. Less maintenance overall.

Cons

• Highest upfront cost. A quality LED fixture costs significantly more than HPS or CMH. Budget LEDs exist, but they usually perform like budget LEDs.
• Quality varies wildly. The LED market is flooded with cheap imports that overstate their specs. Stick with reputable brands and buy from somewhere that can actually advise you (like us).
• Less radiant heat for cold climates. If you grow in a cold garage during winter, you might actually miss the warmth from an HPS. LEDs won’t heat your space the same way.
• Light burn risk. Because LEDs run cool, growers sometimes hang them too close to plants. The light intensity can still burn leaves even without heat stress.

Best For

Growers who plan to run their setup for more than a year or two and want the lowest ongoing costs. Also the best option for warm climates (hello, Queensland) where managing tent temperature is already a challenge. Perfect if you want one light that handles veg and bloom without swapping bulbs.

Head-to-Head Comparison

Here’s how the three stack up side by side. These figures are based on mid-range, quality fixtures in each category.

Factor	HPS	CMH / LEC	LED
Energy Efficiency (umol/J)	1.0 to 1.7	1.4 to 1.9	2.0 to 3.0+
Heat Output	High	Medium	Low
Spectrum	Narrow (red/orange)	Wide (close to sunlight)	Full (tuneable on some models)
Lifespan	10,000 to 15,000 hrs	~20,000 hrs	50,000 to 100,000 hrs
Upfront Cost (hobby setup)	$150 to $350	$300 to $550	$400 to $1,200+
Running Cost (per year, est.)	Highest	Medium	Lowest
Bulb Replacement	Every 9 to 12 months	Every 18 to 24 months	None needed
Dimmable	With digital ballast only	Some models	Most quality models
Best Stage	Bloom	Veg and bloom	Veg and bloom

Which Light is Best for Beginners?

If you’re setting up your first grow tent, we usually point people toward one of two options:

LED if your budget allows it. A quality 200W to 300W LED panel in a 1.2m x 1.2m tent is about as close to “set and forget” as lighting gets. Less heat to manage. No bulbs to swap. Lower power bills from day one. And the even light spread is forgiving for new growers who are still learning plant placement.

CMH if you want great light quality at a lower price. A 315W CMH in a 1.2m tent does a brilliant job. You get that natural white light that makes it easy to spot problems early. And the upfront cost sits comfortably between HPS and LED.

HPS is still a solid starter option if budget is the main concern. Just factor in the extra heat management, especially if you’re growing through a Sunshine Coast summer.

For a full walkthrough on tent setup (including how to match your light to your ventilation), check our grow tent setup guide.

Which Light is Best for Experienced Growers?

If you’ve been growing for a while and you know your way around a tent, here’s what we see experienced growers choosing:

LED for efficiency and control. Serious growers love the ability to dim, tune spectrum, and run cooler rooms. When you’re dialling in every variable, the control that LED offers is hard to beat. The upfront cost stops being an issue when you’re committed to growing long-term.

CMH for quality and natural light. Some experienced growers swear by CMH for the UV output and the way plants respond to that broader spectrum. A 630W double-ended CMH in a larger space produces outstanding results.

HPS for proven bloom weight. Plenty of experienced growers still run HPS in bloom specifically for the heavy yields. Some run a hybrid setup: LED or CMH for veg, HPS for bloom. That combo gives you the best of both worlds.

What We Recommend (Honest Take From 35 Years)

Here’s what we tell people who walk into our Kunda Park shop and ask “which light should I buy?”

For most growers in 2026, LED is the smartest long-term investment. The technology has caught up. The efficiency is genuinely better. The heat reduction matters, especially in Queensland. And you don’t have to think about bulb swaps or degrading output.

But we’re not going to pretend HPS and CMH are dead. They’re not. A quality HPS or CMH setup in the right hands still produces fantastic results. We sell all three types for a reason.

The “right” light depends on your grow space, your climate, your budget, and how long you plan to keep growing. If you’re going to be at this for years, invest in LED. If you want to try things out without spending a fortune upfront, HPS or CMH will get you growing today.

We stock all the major brands and can match a light to your exact setup. Browse our lighting range or come in and chat with us. We’ll steer you right.

Matching Lights to Tent Size

One of the most common mistakes we see is putting the wrong size light in a tent. Too much light wastes power and stresses plants. Too little and you get stretched, weak growth. Here’s a rough guide:

• 0.6m x 0.6m tent: 100W to 150W LED, or a 250W HPS
• 0.9m x 0.9m tent: 150W to 250W LED, or a 315W CMH
• 1.2m x 1.2m tent: 200W to 350W LED, 315W CMH, or a 400W to 600W HPS
• 1.5m x 1.5m tent: 350W to 500W LED, 630W CMH, or a 600W to 1000W HPS
• 2.4m x 1.2m tent: 400W to 650W LED (bar style works great here), dual 315W CMH, or a 1000W HPS

These are starting points, not hard rules. The height of your tent, the reflectivity of your walls, and the type of plants you’re growing all affect how much light you actually need. If you’re not sure, bring your tent dimensions into the shop and we’ll work it out with you.

Want the full tent setup breakdown? Our grow tent setup guide covers ventilation, fans, filters, and how everything fits together.