The old method of growing cannabis in a 4’ x 4’ square is outdated and should be reconsidered due to advances in bulb technology.
A 4’ x 4’ light footprint is great when growing with single-ended HPS bulbs. But the fact-of-the-matter is, there are better bulbs available that can save you money and increase your light footprint.
Double-ended (DE) bulbs have been shown to increase light output within PAR by up to 30%. This increase means that the light footprint of a DE bulb can be increased up to 5’ x 5’ without loss of light within PAR per square foot.
To illustrate this purpose, let’s calculate the micromoles per square foot of each bulb type. For reference:
- A single-ended HPS bulb from Philips produces 1550 micromoles
- A double-ended HPS bulb from Philips produces 2100 micromoles
- Typical ballasts have the option of running a 1000 watt bulb at 1150 watts, this would increase the micromoles of the DE bulb to 2415 micromoles (estimated).
4’ x 4’ equals 16 square feet. Using a single-ended bulb at 1000 watts results in about 97 micromoles per square feet.
4’ x 5’ equals 20 square feet. Using a double-ended bulb at 1000 watts, results in 105 micromoles per square feet.
5’ x 5’ equals 25 square feet. Using a double-ended bulb at 1150 watts, results in about 97 micromoles per square feet.
As you can see, by switching to DE bulbs, it is possible to get the same amount of micromoles per square foot when growing on a 4’ x 4’ light footprint as a 5’ x 5’ light footprint.
By increasing the light footprint in this manner, it is also possible to decrease the amount of equipment – ballasts, bulbs and reflectors – needed in the grow room. In a room with 1600 square feet of canopy, 100 reflectors would be needed if using a 4’ x 4’ configuration, while only 64 reflectors would be needed if using a 5’ x 5’ configuration.
This equals a 36% decrease in the amount of lighting equipment needed, which can result in huge up-front savings. Additionally, the 100 reflectors with single-ended bulbs needed for a 4’ x 4’ configuration would require a total of 100,000 watts. Whereas the 64 reflectors with double-ended bulbs needed for a 5’ x 5’ configuration would only require a total of 73,600 watts. The wattage difference alone will save you 26% of your lighting electricity costs each month.
As you can see, the larger a cultivation facility is, the more of an impact switching to 5’ x 5’ light footprint will have on equipment costs, installation costs and monthly electricity costs.