To Start with, we need to understand that grow lights are often all drastically different from each other. even if they look the same from the outside.

To try to compare different types of lights many people will use total electric watts per $$ or electric watts per square metre.
While this may have worked in the past, it is no longer an accurate way to measure grow lights.
This is because thankfully electricity doesn’t grow plants Photosynthetically Active Radiation, or PAR does.

PAR Rating

PAR is the useful range of light wavelengths that a plant uses to grow. This is measured in uMol.
Grow lights are special types of lights which emit the right type of light (As well as being really, really bright).
That’s why you can’t just get any old high wattage floodlight to stick in your grow tent – you’ll be wasting energy needlessly because the majority of the light probably falls outside of the PAR spectrum.

UV-A & Infrared Light

One exception to this is UV-A and Infrared lights, which have shown to have specific benefits to plant growth.
Most quality LED fixtures will include UV and infra red lighting within their fixtures.

Watts aren’t accurate

It all sounds pretty simple, but the majority of Grow light manufacturers still advertise grow light intensity as a Watts figure, since it’s easier to make a claim based on how bright the light appears. It is very hard to design an energy efficient grow light (within the PAR range). It is very cheap and easy to build a light which delivers high light levels and also uses a lot of electricity since energy efficient components such as drivers, LED Boards, and Reflectors are very expensive. Most manufacturers will choose to save costs and will fit cheaper components while still claiming a high wattage figure.

LED boards come in all shapes and sizes, and it’s important to take note of the PAR graph of your grow light to see how much light your fitting produces in each part of your grow tent and at multiple heights. It would be easy for a manufacturer to take the highest uMol reading directly under the light and advertise this as the output.

Light Spectrum

It’s also very important to consider the light spectrum of the product you are buying.
To compare some of the main LED Quantum board brands The Mars Hydro utilizes a combination of 3000K-3200K & 6000K-6500K. Spider Farmer has 3000K and 5000K, HLG uses only 4000K.
Generally we are trying our best to replicate sunlight, so the broader the spectrum the better.

Quantum Board & Driver Compatibility

It’s also difficult to know, even with some of the later generation Quantum board LED’s whether you are buying a quality fixture or not.
The LED’s themselves, the drivers, the shade, and the cables and plugs will all be purchased from seperate suppliers.
Some companies will deliberately ‘overdrive’ their units, which means running the LED’s and drivers close to maximum load constantly. This may mean cost savings on lesser components, but the light could overheat and may fail much sooner than it should.

It is also very important to consider the energy efficiency of your grow light for instance, The Mars Hydro TS3000 has a PAR reading equivalent to a 1000W HPS Bulb and Pulls 450 watts from the wall. The light intensity does not decrease much as you move away from the center of the fitting.

Since this is a very efficient fitting it produces relatively low levels of heat. You can also remove the driver and place it outside the tent to reduce heat inside the tent further.