1 kilo per light - or why gm/watt suck!

Growroom Design
16

Time can be taken into equation easily. I remember that on old OG, so called “Garden Efficiency Index / GE index” was used to compare gardens. It reflected how much yield was produced by 1 kWh of light energy.

Hypothetical example with 2 pieces of HPS 600 W and 1kg yield.

  1. You need to find out how many kWh your light consumes. Take your watt draw and divide by 1000.
    2 * 600 / 1000 = 1.2 kWh
  1. How much energy did you spend on vegging and flowering?

  • Vegging: 18/6 cycle for three weeks, that is
    18 hours * 21 days = 378 hours

  • Flowering: 12/12 cycle for 60 days
    12 * 60 = 720 hours

  • Total: 378 hours + 720 hours = 1098 hours

  1. Multiply number of hours by kWh your lamp consumes.
    1098 hours * 1.2 kWh = 1317.6 kWh

  2. Take total yield in grams and divide it by kWh: (Hypothetical 1kg yield)
    1000 grams / 1317.6 kWh = 0.76

  • Resulting GE index = 0.76

Grams per Watt can work when comparing standard grows with average veg and flower times. For unusual techniques (really short or really long veg times), GE index (grams per kiloWattHour) is much better.

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