HPS vs. CFL Grow Lights: The Key Differences for Cannabis

When it comes to lighting for growing plants, HPS and CFL are two popular cannabis grow lights with very different personalities. High-pressure sodium (HPS) bulbs are powerful, run hot and shine in the flowering stage, while compact fluorescent lights (CFLs) are cheap, cool-running and low-wattage, best suited to seedlings, clones and small spaces. Those differences shape your plants' growth, your power bill and plenty more.

In this guide we dig into the main differences between HPS and CFL bulbs so you can make an informed call on which one fits your grow.

What is an HPS grow light?

HPS lamps are a go-to in horticulture because they put out a yellow-orange light that's especially good for the flowering or fruiting stage.

Sodium lamp technology goes back to the 1930s and has come a long way since. Made by companies like Philips and Osram, high-pressure sodium lamps deliver an intense red-heavy spectrum that's ideal for pushing growth during bloom.

Their use has dropped in some places because their light is harsh on the human eye, but HPS lamps are still widely used in horticulture, especially in regions with little natural sunlight, like Northern Europe.

Why are HPS lights so popular?

Compared with other options like LED grow lights, HPS bulbs are still a popular pick, mainly because of how they perform in flower.

They come in a range of wattages, from 250 W to 1,000 W, and can carry a plant through the full grow and bloom cycle, depending on what your grow needs.

To get the most out of them, it's recommended to swap your HPS bulb roughly once a year, or after four full grow cycles. Bottom line: HPS lamps are still a reliable, effective option for growers chasing top results.

What are CFL grow lights?

If you're looking into CFLs (compact fluorescent lights) and how they fit into growing, you're in the right place. A CFL bulb is a popular indoor lighting option, known for its energy efficiency and its ability to deliver decent light at a low price.

These bulbs are a spin-off of industrial fluorescent tube technology, and they stand out for their compact size: the glass tube is folded or coiled to fit into a small bulb. With a screw-in base that carries the current and a built-in electronic ballast, CFLs bring plenty of perks, like low power draw and very little heat.

CFLs trace their roots to pioneers like Peter Cooper Hewitt, who invented the low-pressure mercury vapor lamp. Over time, advances led by people like Hans Spanner, Friedrich Meyer and Edmund Germer improved the efficiency and quality of these bulbs.

Why do so many growers look for CFL bulbs?

In growing, especially for seedlings and clones, CFLs are popular because they sip power and don't cost much. And since they barely put out any heat, they're great for small grow spaces.

That said, CFLs have their downsides, like relatively low yields and light intensity that drops off quickly with distance. To get the most out of them, you have to adjust your grow conditions, like how close the plants sit to the bulb and how much you water.

You'll find plenty of CFL models out there, from 25 W up to 300 W, including specific versions for vegetative growth and for flowering. It's recommended to replace CFL bulbs after roughly 18,000 hours of use to keep them performing.