The Cannabis Grow Bible
by Greg Green
Wattage and Lumens
HID Lights can range anywhere between 75W and 4000W. In general the stronger the wattage v we must also consider another factor and that factor is called Lumens. Lumens are the correct way of measuring how much light per square foot a bulb emits. Lumens and wattage do go hand in hand but can vary a large amount between systems. The better the lighting kit, the better the lumens it will cast. Lumens have more to do with the design of the light than the wattage of the light itself. Some 600W lights may give the same lumens as a 400W light.
This is interesting because we have two types of HPS lights using the same bulb wattage and one of the types is casting more Lumens than the other. The reason for this is that the higher lumens kit is better quality than the other. So we now know that some lighting kits produce better Lumens than others. Check through HID lighting kits and look at how many lumens they cast. This is a good indicator of how professional that light is. Also a 4000W HID is too much for one single plant. A 1K bulb is the maximum limit per light you should use. Use several 1K bulbs if you need more light. A 4K bulb will bleach Cannabis and is very hot.