Most important criteria for choosing grow lighting

Grow lights are the centrepiece of every grow box or indoor growing room, and it is worth paying them plenty of attention when choosing them. This is by no means only about electricity consumption – more important are parameters such as the light spectrum, efficiency and even coverage of the growing area. Modern LED technology offers higher efficiency than older HPS discharge lamps, as well as the option to adjust light conditions. In this article, you will learn how to choose the right LED grow light from a wide range of options for your exact needs.

Consumption is not everything

In the past, growers focused primarily on input power expressed in watts (W) when choosing lighting. From this figure, you can easily calculate consumption and at the same time obtain a rough estimate of how much light energy plants will have available for photosynthesis. Contrary to general belief, however, the input power of a light is not the best measure for assessing how much light from grow lighting reaches the plants. The true measure of a light’s performance lies in the amount of light energy it delivers to plants in exchange for the electricity consumed.

PAR (photosynthetically active radiation) is an abbreviation for photosynthetically active radiation, that is, light of such wavelengths that plants use during photosynthesis. The photosynthetically active light spectrum roughly corresponds to that visible to the human eye (400-700 nanometres). The most efficient grow lights are those that most effectively convert the supplied electrical energy in watts (W) into the greatest number of photons in the PAR spectrum, measured in micromoles (µmol). While the most efficient HPS grow lights emit approximately 1.4 to 1.8 µmol/W, the best LED lamps achieve almost double the efficiency, up to 2.8 µmol/W. To produce the same amount of photons in PAR, the most modern LED diodes require almost half as much electricity as HPS discharge lamps.

Each wavelength in the PAR spectrum (light colour) has a different effect on plants. Light in the red and blue parts of the spectrum has the most pronounced effect on plant growth. Blue light stimulates plants to grow quickly and form new leaves and stems, which is important for them during the vegetative growth phase. Red light supports flowering and ripening and encourages them to grow taller. However, plants use all colours of the light spectrum, including those outside PAR. For example, exposure to infrared and ultraviolet light leads to increased production of resin and secondary metabolites. In general, most LED lights emit light in the PAR spectrum, but you can also find specific models with UV and infrared wavelengths.

Consider the quality of the LED diodes

Manufacturers of LED grow lighting like to talk about the quality of the LED diodes they install in their lights. LED diodes are small semiconductor chips that convert electrical energy into light and at the same time determine its wavelength. High-quality LED lights use diodes with an output of at least 3 W. The lower the diode output, the lower the intensity of the emitted light will be. The standard for measuring light efficiency is micromoles per joule (μmol/J).

PPF (photosynthetic photon flux) is an abbreviation for photosynthetic photon flux, that is, the amount of photosynthetically active photons that a light source emits per joule of consumed electrical energy. Some manufacturers also express PPF in micromoles per second (μmol/s). PPF in cheap LED grow lamps ranges from 0.8 to 1.5 μmol/J, while quality lights achieve up to twice the efficiency.

In addition to (PPF), the efficiency of a grow light can also be expressed by photon flux density (PPFD). This metric tracks the amount of photosynthetically active photons falling on a given surface per second (μmol/m²/s). The older the plants are, the more light they are able to tolerate and use effectively during photosynthesis.

• PPFD for seedlings: 200 to 400 μmol/m²/s
• PPFD for plants in the vegetative growth phase: 400 to 600 μmol/m²/s
• PPFD for the flowering phase: 600 to 1000 μmol/m²/s
• If you use CO₂: up to 1,000 μmol/m²/s during the growth period and up to 1,500 μmol/m²/s during the flowering period.

What else not to forget when choosing LED grow lighting

In addition to technical parameters, other factors also play a role when choosing the right lighting for your grow room. Ideally, the light intensity should be the same across the entire growing area available to you. For example, Maxibright Daylight PRO Full Spectrum LED with an input power of 300 W covers a growing area measuring 1x1 metre. The SANlight EVO 3-60 grow light with an input power of 200 W covers only an area of 0.6x0.6 metre, and for medium-sized tents it is better to use two models of this type at once.

Another aspect is the angle at which light from the LED diodes falls on the plants. The wider the angle, the larger the area the LED diode illuminates, but at the same time the light intensity and penetration decrease. The standard for most grow lights is LED diodes with a beam angle of 120°. Additional functions such as dimming, external control or the option to adjust the spectrum are not essential, but they can make life easier for the grower.

Our final point is that before buying grow lights, you should always take the price-to-quality ratio into account. Although the cheapest equipment may seem like a major saving, it often offers a shorter lifespan and outdated technology, and in the long term it does not pay off.

Are you unsure when choosing equipment for indoor growing? At Higarden, we have you covered! Visit our growing blog or contact our expert sales staff.