LED grow lighting

How to choose LED lighting for plants

LED lights are used in home and commercial grow rooms. Compared with less efficient discharge lamps, efficient models deliver more photosynthetically active photons per watt of power. At a comparable light output, they can therefore reduce energy consumption and heat load; at the same power, less heat cannot automatically be expected. For the whole cycle, choose a model with a spectrum designed for use from seedlings to harvest. The main factors in choosing are the size of the area, the light's efficiency and the evenness of the light across the entire crop.

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Watts, PPF, efficiency and PPFD

• Power (W) indicates the rate of electrical energy consumption. It does not tell you how much light the plants receive.
• PPF (µmol/s) is photosynthetic photon flux: the quantity of photons in the PAR range (400–700 nm) emitted by a light per second.
• Efficiency (µmol/J) is the ratio of PPF to the light's electrical power. Selected models in our range are listed at approximately 2.5–3.1 µmol/J, for example Maxibright Daylight PRO 300W at 2.5 µmol/J or LAZERLITE PRO 720W at 3.1 µmol/J.
• PPFD (µmol/m2/s) is the density of photosynthetic photon flux reaching a unit area per second. It depends, among other things, on the hanging height, optics, light distribution and reflections; measure it at several points above the crop.

Output according to tent size

The table gives indicative examples from our range, not a universal recommended power. It takes the specifications and areas from the e-shop product descriptions; some could not be independently confirmed with the manufacturer. Check suitability for a specific crop against the PPFD map, lighting duration and instructions for the model in question.

Examples of light levels with 16 hours of lighting per day

The values are rounded examples converted from Virginia Cooperative Extension recommendations: seedlings and cuttings DLI 5–10, lettuce 12–17 and tomatoes 20–30 mol/m2/day. They apply to an approximately constant intensity over 16 hours per day and total light including daylight. DLI = PPFD × number of hours × 0.0036. Needs vary according to species, variety and conditions; 16 hours is an example for the calculation, not a universal day length. Read more in the article The most important criteria for choosing grow lighting.

Main lighting or supplementary lighting

A main light above the crop can be supplemented with under-canopy lighting: under-canopy panels illuminate leaves that the main light cannot reach. Bars with a far-red component (around 730 nm) are added to the main light to supplement the spectrum, not replace it. The article Supplementary lighting for lower levels: under-canopy and inter-canopy explains how to choose them.

Smaller lights can also be used for smaller areas with seedlings, cuttings or microgreens, provided there is sufficient PPFD and lighting duration: TLED tubular LEDs or smaller lights from the Supplementary lighting category. Find tips in the article Choosing lighting for growing microgreens.

Which LED brands you can find here

• Maxibright: Daylight and Varidrive ranges; check the specific model for dimming options.
• SANlight and Lumatek: premium lights (SANlight EVO and STIXX, Lumatek ZEUS and ATTIS) for demanding and commercial grow rooms.
• AC Infinity: LED panels and bars; connection to AC Infinity controllers depends on the compatibility of the specific model and interface. They can be combined with their tents and ventilation.
• SunPro: full-spectrum LEDs, SUNBOARD, SUNDOCAN, MAMASUN and HITTER ranges. For example, according to the e-shop product description, HITTER 720W has an efficiency of 2.9 µmol/J.
• FAVEN: under-canopy lights; according to the manufacturer, the Chroma range offers an adjustable spectrum and separate far-red control.
• TLED: energy-saving tubular LEDs for supplementary lighting for propagators, seedlings and cuttings.
• VIVOSUN: LED lights for VIVOSUN grow tents.

More brands and selections: 720W LED lighting, Lazerlite, Secret Jardin, Mars Hydro, ViparSpectra, Vanguard Hydroponics, LUMii Black, ThinkGrow, Adjust-A-Wings, Dimlux, Powerplant, Trafika, other LED lights. Find a light with accessories in one pack in the LED kits category.

Controls and dimming

High-output LEDs can be controlled externally. Use control units and timers to set the lighting duration. Dimming, temperature response and joint control of multiple lights require compatible control units and lights; a timer alone cannot provide these functions. Dimming helps adjust PPFD to the needs of seedlings and mature plants.

Frequently asked questions

How many watts of LED lighting do I need for a tent?

The examples in the table can help with an initial choice, but the area alone does not determine the wattage needed. The crop, target PPFD, lighting duration, efficiency and evenness of light all matter. Check the documentation for the specific model for PPF, coverage and actual power; the model name may not exactly match its power.

Are LEDs better than discharge lamps?

Efficient LEDs can reduce energy consumption and heat load compared with less efficient discharge lamps at a comparable light output. A light with a spectrum for the whole cycle does not require the light source to be changed between vegetative growth and flowering. Compare the purchase price of specific setups. Find a detailed comparison in the article HPS vs. LED.

What does µmol/J mean and why does it matter?

It is a measure of efficiency: how much photosynthetically active light a light produces from one joule of electricity. At the same power, a light rated at 3.0 µmol/J produces 20% higher PPF than one rated at 2.5 µmol/J, if both figures are measured for the complete light in the same PAR range. This does not automatically mean the same difference in PPFD across the crop.

How high should I hang the light?

It depends on the light's power and the growth stage. Follow the instructions for the specific model and measure PPFD. For example, the e-shop product description for LAZERLITE PRO 720W gives an indicative distance of 20–60 cm above the tops; check the instructions for the supplied version. If the light is too close, leaves may scorch; if it is too high, intensity is lost. Guide: How high to hang grow lights.

What are under-canopy and far-red?

Under-canopy refers to panels or bars placed in the lower level of the crop. Far-red is long-wavelength red light around 730 nm, which manufacturers add as a separate channel or supplementary bars. Both supplement the main light; neither replaces it.

Are LEDs suitable for herbs, chillies or microgreens?

Yes. For a small area, you can use a smaller panel or a suitable TLED tube, provided it delivers the required PPFD and daily light integral. Find specific tips in the articles What is the best light for growing chillies? and Lighting for microgreens.

Guides from our blog

• The most important criteria for choosing grow lighting
• Growing under artificial lighting: HPS vs. LED
• The light spectrum and its effect on plant growth
• How high to hang grow lights
• How to choose LEDs for under-canopy and inter-canopy
• Lighting for plants: what and how to use for supplementary lighting

Not sure which one to choose? Write to us at info@higarden.eu and we will recommend a light for your area and budget.