### How to use our Grow Light Efficiency Calculation Tool to size your grow light

This is a simple and accurate grow light efficiency calculation tool. You can use the grow light efficiency calculation tool for most grow light systems such as CFL, HPS, MH, CMH and LED.

The first step is to use the known PPF/Watt (Photosynthetic Photon Flux/Watt, the measure of light used by plants per unit of energy consumed) of the most common grow light technologies. This information is available from manufacturers data sheets.

Next we estimate the efficiency of the reflector or lens being used in the grow light system. The figures here are likely to range 10% higher or lower for high quality and low quality components respectively. We have used an average in the calculation sheet.

The walls of the grow area are the next critical factor. No walls will result in a lot of lost light. Low quality reflective walls such as matt white or budget tent lining will also result in relatively high light loss. The top tip is to use silver mylar to minimise reflective light losses to only 10%. MIGRO uses a hanging system and lenses to focus 95% the emitted PAR light onto the plant canopy.

The last component is the LED driver or ballast for the HID and CFL technology. The lower quality systems efficiency may be as low as 70% and the best 95%.

To do your own calculation follow these steps:

Select your grow light technology. Example: HPS SE – 1.9umol/watt

Select your ‘Optics’ type. Example: Reflector – 85%

Select your grow room walls. Example: Silver Mylar – 90%

Select your power supply efficiency. Example – Digital ballast – 95%

Multiply the above together to get the system efficiency. Example: 1.9 x 0.85 x 0.9 x 0.95 = 1.38umol/watt

We have tested many different grow light systems and cross checked the actual results with the calculator and the outcomes are very close.

You can use this calculator to accurately size your grow light for your grow area.

Calculate how big a grow light you need for your grow space here

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I’ve never seen anyone provide this info before. Impressive stuff. Many thanks.

I’ve got a question: for CFL bulbs, they often quote two wattage numbers. For example, they quote a CFL bulb of 23 Watts, which is equivalent to 100W incandescent bulbs.

In your formula, the CFL “watt” corresponds to which ? 23 Watts or the 100W incandescent equivalent?

Thanks,

Hi Tony, the calculator tool uses the power consumed by the bulb, not the equivalent incandescent bulb number. You still have to be careful though as many of the large CFL bulbs of 100W and greater are badged as a certain wattage but draw much less. For example the Electrox 250W CFL I used recently in a test drew only 200W from the wall. That’s 20% less than the rated wattage.

I’m working on one hectar corn grow cultivar with high seed density. I need a strip led lamps the most hard wording and waterproof ones.

My proyect is to lay down the strip directly on the ground at the open air cultivar (no greenhouse) Why? A high level developed cultivar means normaly plants with wide leaves and dense canopy. But it happens sometimes that this kind of plant development does not let the solar light get through the lower leaves and that causes low productivity because the lack of a total photosynthesis. And at least you have another solution, given your notorious led grow knowlege, I arrived to the conclution I have no choice but to use a hard work waterproof strip, trying to give light only to the posible maximun of lower leaves. In a such situation of a high leaves density I have not room for a ligth spectrum and that is the reason I am planing to install the strips at one meter interlines of 100 hundred meters long. In that sense, please help me by giving the equivalence of the he blue wave length 450nm and red wave length 660nm in terms of lux, lumens or mols. Given my special agronomical circunstance ¿ could you recomend to me the ideal strip?

Thanks Again. Antonio

K

Can anyone help me with this led light i have for grow tent space of 1.2m 1.2m 1.8m heigh all reflected i side the tent just not sure on this ligh i have time to send back and buy a braned one i know more about all info i have on tbe light is…. specifications

1200W LED Grow light

Model: 200W

LED Quantity: 120PCS exclusive 10W Double Chips LED

Actual Power: about 120W±10% power, much better than the same product in market

Spectrum: 410-475nm , 620-660nm ,3000K 6000K

LED Brand: High Intensity Epistar Chip

Input voltage: AC 85-265V 50/60Hz

Lumen: about 1600 lumens

Coverage Area: 2.5*2ft for Veg, 2*1.5ft for flower

Decibel of the light: About 56DB

View Angle of LED: 90/120 degree Mixed

Lifespan: ≥50000hours

Size: approx.310*210*60 cm

Its a 1200w light but says actual power 200w so is that the actual power output of the light lost wish i just bought a more common used light for the plants dont want to start with a wrong light or not enough light.. thanks for any help..

Hi Andy, unfortunately many grow lights are advertised with misleading wattage and coverage figures. You should only buy a grow light with published output in PPFD and with a PAR intensity map showing the PPFD readings across the recommended grow area.

Hello Andy, the light you have bought probable delivers about 1umol of PAR light to the plant canopy (PPFD). At 120watts x 1umol = 120 umols of PAR light (PPFD). A flowering plant needs a minimum of 500umols per metre squared of PPFD. Your light will cover 120/500 = about 0.25 metres squared. Thats about 50cm x 50cm or one small plant. You would need at least four of those lights to get reasonable growth in a 1.2m x 1.2m tent. You would need 6 or 7 of them to equate to our MIGRO 400 (thats what we recommend for a 4×4).

What is the life expectancy of the LED’s? Do they lose efficiency over time and if so how much? I know spectrum king LEDs advertise 10% loss after three years but not much info beyond that.

Hello Brad, The lifespan of LED’s is dependent on the LED and the temperature it being run at. Run at lower temperature and the lifespan will be longer. Our LED’s will maintain 80% of their initial output after 50,000 hours (about 8 years growing). The output declines linearly so at about 2.5% per year of growing

Hi Shane,my tent is 2 m x2m x1.8 h can u tell me will the 600 migro be enough for the tent , thanks Danny

Hi Danny. a 2m x 2m tent is 4m2 total area. You need about 600umols PAR light per m2 (PPFD) so you need 4 x 600 = 2,400 umols PAR light (PPFD). The 600w HPS will output about 700umols (PPFD)so you would need at least three of them, ideally four. Its a very big grow area to cover so needs lots of light!

Can a LUX Meter accurately measure light output of “white led”? Thank you.

Hi, yes they can and you can setup successfully with a lux meter as you can map out the hot spots and weak areas with a lux meter.

Thank you Shane for sharing your knowledge!

Hey Shane , I bought the original Array 2 without red enhancement when they first came out. I also bought the A881E lux meter. The plants love the light but I haven’t used the meter because I’m a dummy. Could you please tell me the formula to use with my particular light and how to convert The Lux into PPFD into DLI. Much appreciated Mitch

Thank you for this information, it helps especially umol/watt numbers. However I disagree with formula and some efficiency numbers provided. Only reflected light is affected by the walls, not the direct one. Also when using lens focus, formula wants to multiply 95% and 95% which results in total 10% losses. However, absorption rate in clear glass lenses is 2% (depends on wavelength but accepted average is 2%), so in such setup 98% of emitted light hits the plant canopy, not 95%x95%=90.25%.