When you are going to run a grow room, you must know how to calculate the electricity consumption, then you wouldn’t be shocked by monthly energy bill.
But how to calculate the electricity a LED grow light use? There are three important factors you must figure out.
-
Wattage of LED grow light
-
Working time of LED grow light per day
-
Electricity rate
What wattage LED grow light do your plants need?
Just like you must buy proper shoes size to your feet, you should choose correct LED grow light for your lovely plants.
A reasonable rule-of-thumb for you to calculate is that 25-40 watts LED grow light per square foot of growing space for large flowering plants.
For example, your grow tent is 4x4ft footprint for medical flowering, the suitable wattage should be 4feet x 4feet x 40 watts= 640 watts.
Of course you could choose higher wattage LED grow light and dim its light intensity for different stages. But too much light will hurt your plants. Because strong light and heat will destroy the chlorophyll in the leaf. The result comes to pale, bleached and faded areas on the leaf. And the leaf color finally becomes brown and dark.
Therefore, it is necessary to choose a suitable LED grow light for your plants.
How long should LED grow light work per day?
It depends on the crops you grow in your grow room. Cannabis needs 18 hours of light per day in the growth stage and 12 hours of light per day in the flowering stage. If you grow lettuce and other leafy greens, they usually need 14 hours of light per day. You can decide the working hours of the LED grow light based on your own experience. And the plants will respond to the light. Too little light will weaken the plants, and too much light will burn the plants.
If your grow room is built with a glass roof and transparent walls, the plants can grow in the sun during the day. Then the LED grow light only needs to work in the morning and evening. It can save a lot of energy consumption.
How much is electricity rate in your city?
If you are going to grow a few plants in a grow shed, you only need to use residential electricity. But if you have a large greenhouse, you should use commercial electricity. Usually commercial electricity is a little cheaper than residential electricity.
For example, the average New Jersey commercial rate is 14.2 ¢/kWh, but the average New Jersey residential electricity rate is 17 ¢/kWh.
In Australia, the price of electricity is 22.1 c/kWh for households and 18.5 c/kWh for businesses.
Before you build your own grow room, it is necessary to investigate the local electric rate, low electric rate will save you a lot of money.
How to calculate the electricity a LED grow light use?
After we make above three factors clear, things become quite easy to calculate the electricity cost now. Here is a calculation formula for your reference:
Monthly Electricity Cost(USD) = Power consumption(kWh) x working time(Hours) x Electricity Rate (USD/kWh)
For example, you have 3 units 1000w LED grow light in the grow tent in your house, the total power wattage is 3 x 1000 watts = 3 000 watts. It means the power consumption is 3000 watts / 1000 = 3 kWh. (In this example, power output 1000w is a theoretical data, as we know the LED grow light doesn’t always work with full output. But it doesn’t matter for us to use this maximum data to calculate the electricity cost.)
The LED grow lights work around 12 hours per day. Then their monthly working time is 12 x 30 = 360 hours
And if your house is located in New Jersey, the residential electric rate is 14.2 ¢/kWh.
All details is clear. Let’s put all above data into the calculation formula.
The monthly electricity cost is equal to 3 kWh x 360 hours x 14.2 ¢/kWh = 153.36 USD.
It means you have to pay 153.36USD per month for your grow lights.
Let's take another example, you have a greenhouse in Australia with a total of 20 800-watt LED grow lights. The plants can receive sunlight during the day, leaving the grow lights on only 6 hours after sunset. Let's calculate how much you will receive in electricity bills at the end of the month.
Total wattage is 50 x 800 = 40 000 watts. It means the power consumption is 40 000 / 1000 = 40 kWh.
And the LED grow lights monthly working time is 6 x 30 = 180 hours.
Also we know the Australia electricity rate is 18.5 c/kWh for businesses.
Then the monthly electricity cost is
40 kWh x 180 hours x 18.5 c/kWh = 1 332 USD.
It means you will receive a electricity bill with 1,332USD at every month.
Do grow lights take a lot of electricity?
At last, we can answer the question. And every growers care about the result. If you understand above calculation, you will say the result is pending.
The answer is probably yes. If you run a grow room, the electricity bill will be a big one. Especially if you need to run it every day. Although your greenhouse has sunlight during the day, the effect will also decline in the winter, and LED grow lights will play an important role in this period.
But the answer could also be no. LED grow light is widely used in grow rooms in now days, we could see it in vertical farming, container systems and many greenhouse projects. Comparing to traditional lamps, LED grow light can provide more efficient light than HID, HPS and other lamps. You can use same electricity but grow more plants with LED grow light. We believe you could get the maximum benefit by LED grow light working in your grow room.
Note: Reprinted from VANQ