For years, growers have used the gram-per-watt scale to measure their blooming room’s efficiency. For example, Gardener A was using 2000 watts and harvested 1000 grams. Gardener A would have an efficiency rating of .5 grams per watt of energy consumed. This is a good basic scale, but I always had a problem with the time factor. Let’s say Gardener B uses the same wattage and produced the same yields as Gardener A but can do it in 20 days less. Under the old grams per watt rating Gardener A and Gardener B would have the same efficiency rating. Obviously this is inaccurate because the ability to harvest in less time allows Gardener B to have more harvests per year and is, thus, a more efficient gardener. This is why measuring the gram per watt alone isn’t sufficient for calculating efficiency.
The most accurate way to measure efficiency for a medical marijuana garden is to measure the amount of grams produced per kilowatt hour. Let’s compare Gardener A and Gardener B with time factored into the equation. Gardener A uses 2000 watts and produces 1000 grams in 80 days. Gardener B uses the same wattage and produces the same yield in 60 days. Here is how their efficiency should be measured:
Step 1. Divide total wattage used by 1000 to determine the kilowatts.
Gardener A: 2000/1000 = 2 kW
Gardener B: 2000/1000 = 2 kW
Step 2. Multiply the kilowatts by hours in the light cycle (blooming is usually 12 hour light cycles) to find the kilowatt hours per day.
Gardener A: 2 kW x 12 h = 24 kWh per day
Gardener B: 2 kW x 12 h = 24 kWh per day
Step 3. Multiply the kWh per day by the total number of days in the blooming cycle.
Gardener A: 24 kWh per day x 80 days = 1920 (total kW hours per blooming cycle)
Gardener B: 24 kWh per day x 60 days = 1440 (total kW hours per blooming cycle)
Step 4. Divide grams by total kilowatt hours to find the grams per kilowatt hours of the blooming cycle.
Gardener A: 1000g/1920 total kilowatt hours = .52
Gardener B: 1000g/1440 total kilowatt hours = .69
Gardener A has an efficiency rating of .52 grams per kilowatt hour. Gardener B has a better efficiency rating of .69 grams per kilowatt hour. As you can see, this method is a much more accurate measure of efficiency. Use this equation to compare harvests on your quest to maximize your room’s potential.