Quick answer: Match the light's coverage to your tent's floor area, not just its wattage. As a rough guide from the lights we sell: a 0.6m tent suits a compact 200W to 300W LED, a 0.8m tent suits around 300W to 360W, a 1m tent suits a 300W to 360W light run near full power, a 1.2m tent suits a 660W to 720W bar-style LED, and a 1.5m tent needs a 720W light rated for that area or more. Always check the coverage the manufacturer quotes for that model.
Why wattage alone does not tell you enough
Wattage is how much electricity a light draws, not how much useful light it gives your plants. Two 720W LEDs can perform quite differently depending on the quality of the diodes and how the light is spread.
Two figures are more useful when comparing lights:
- PPF (µmol/s): the total amount of plant-usable light the fixture puts out.
- Efficacy (µmol/J): how much of that light you get for each unit of electricity. Higher means cheaper to run for the same output.
For example, the Photon 720W LED is listed at a PPF of 2304 µmol/s and an efficacy of 3.2 µmol/J, and the Maxibright Varidrive 3.0 720W at 2160 µmol/s and 3.0 µmol/J. Both are 720W, but the numbers tell you more than the wattage does.
The other thing that matters is coverage: how evenly the light reaches the corners of your tent. A powerful light with a hot spot in the middle and dim edges will give you uneven plants.
LED size guide by tent size
These are general starting points based on the coverage our suppliers quote for the lights we stock. If a particular light's manual says something different, follow the manual.
0.6m x 0.6m tent
A small tent like this is ideal for herbs, salad leaves, a couple of chilli plants, or as a dedicated space for young plants. A compact LED of around 200W to 300W is plenty. The Omega Infinity Pro 200W is designed for smaller tents, and the 300W version is listed for tents from 60cm x 60cm up to 100cm x 100cm.
Avoid putting a big 720W light in a small tent. It will not fit properly, it will be hard to hang at the right height, and you will be paying for light that lands on the walls.
0.8m x 0.8m tent
This is a nice size for a handful of pepper or tomato plants. Look at lights in the 300W to 360W range. The Maxibright Varidrive 360W is quoted for tents from 0.8m x 0.8m up to 1.2m x 1.2m and has a slim 570mm x 590mm footprint, so it sits comfortably in an 80cm tent.
1m x 1m tent
A 1m tent sits between sizes. A 300W to 360W LED run near full power works well here, and the Omega Infinity Pro 300W is listed for tents up to 100cm x 100cm. Some growers prefer a larger light dimmed down, which gives more headroom later. Just check the fixture's physical size fits inside the tent with room to adjust it.
1.2m x 1.2m tent
This is the most popular tent size in the UK, and it is where 720W bar-style LEDs come into their own (more on why below). Good options include the Omega Black 720W, the Gorilla GEN-III 720W and the Photon 720W. The Maxibright Daylight 660W is also made with a 1.2m x 1.2m tent in mind.
1.5m x 1.5m tent
A 1.5m tent has over 50% more floor area than a 1.2m tent, so a light that is perfect at 1.2m can leave the corners short. Choose a light whose maker specifically quotes 1.5m coverage, such as the Maxibright Varidrive 3.0 720W, which is listed as suitable for 1.2m x 1.2m to 1.5m x 1.5m areas, or step up to a higher output fixture. Ask us if you are unsure, as this is where getting it right makes the biggest difference.
Why 720W bar lights suit a 1.2m tent so well
- The footprint fits. Most folding 720W bar lights are just over a metre square. The Photon 720W measures 1043mm x 1083mm and the Varidrive 3.0 720W measures 1080mm x 1050mm. In a 1.2m tent that leaves a little space around the edges to hang and adjust it without catching the walls.
- Even spread. Six or more bars spread the light across the whole canopy instead of one bright central spot, so plants at the edges grow at a similar rate to those in the middle.
- Low heat. Bar LEDs run passively cooled with no fans on many models, which keeps tent temperatures easier to manage than an HPS lamp.
- Built-in drivers and dimmers. Many have the driver built in and an onboard dimmer, so you can turn them down for seedlings and up as the plants grow.
How high to hang your LED
Every light is different, so the manual comes first. As an example, the Omega Black 720W guidance is around 30 to 60cm above the canopy for seedlings and leafy growth, and 45 to 90cm for flowering, adjusting by how the plants respond. If leaves start to bleach or curl upwards at the top, raise or dim the light. If plants are stretching with long gaps between leaves, they probably want more light.
Lights for young plants and the lower canopy
Seedlings and cuttings need far less light than mature plants. A small propagation light such as the Omega 18W Clone LED twin pack over a propagator is cheaper to run and gentler than a full-size LED. For tall plants like tomatoes, an under-canopy bar can help lower leaves and fruit get light.
FAQs
Can I use a bigger light and just dim it down?
Yes, as long as it physically fits the tent with room to move. A dimmable light gives you flexibility, but a fixture that is wider than the tent will waste light on the walls and be awkward to hang.
Is a 600W HPS the same as a 720W LED?
No. They work differently. A good LED will usually give similar or better results while using less electricity and producing less heat. Compare PPF and efficacy rather than wattage.
Do I need a separate light for flowering?
Not with a full-spectrum LED. The lights we sell are designed for the whole cycle, from young plants through to flowering and fruiting.
Which is best for a 1.2m tent on a budget?
Our Bay6 1.2m kit with a Photon 720W LED includes the tent, light, fan, filter and ducting for less than buying everything separately.
Not sure which light to choose?
Bring your tent measurements into our shop at Unit 2 BlackLake, West Bromwich, B70 0PJ, call 0121 553 7872, or WhatsApp us. We will tell you honestly which light suits your space. Free UK delivery over £99, and we price match. You can also browse all our LED grow lights.