HOW MANY WATTS OF LED POWER DO I NEED COMPARED TO HID LIGHTING?
Generally, a 1:2 ratio is best --- 1 watt of LED to 2 watts of HID. Remember, that this is actual LED wattage, not the advertised LED wattage. For example, a 3 watt LED, may only draw 1.7 watts, so the actual output is less than the advertised wattage.
ADVERTISED LED WATTAGE
Another way to look at this is to plan for 40 watts of advertised wattage per square foot of grow space. For example, a light may have 90 x 3 watt diodes. The advertised wattage would be 270 watts (90 x 3 = 270). 270 watts / 40 watts per square foot = 6.75 square feet. Therefore, a 270 watt light will cover 6.75 square feet of grow space.
ACTUAL LED WATTAGE
You may also use the actual LED wattage to calculate the amount of watts you need for your grow space. In this case, you will want 25 watts of actual wattage per square foot of grow space. For example, the 270 watt light described above may only draw 157 actual watts. Say, your grow space is 6 square feet. 6 square feet x 25 actual LED watts = 150 required LED watts. 150 required LED watts is less than the manufacturers suggested wattage for this amount of grow space, therefore this would be the correct LED light for your grow. Yet, it is best to follow the manufacturer's recommendation because all LED units are designed differently.
PPFD
Targeted spectrums, in addition to LEDs efficient design, allow better plant growth while cutting energy costs by about 50%. Home-growers, greenhouse managers, or research scientists can save a lot of money and grow better plants with LED grow lights.