A 500 watt LED grow light in a 4ft x 4ft space will cost about $450 in electricity per year. This is based on an electricity rate of 17c per kilowatt hour and 15 hour light schedule.
How to reduce grow light electricity consumption in your grow room
The cost of electricity is rising rapidly all over the world and increasing the cost of growing indoors. So how much does a LED grow light cost to run and what can you do to reduce the electricity costs?
The grow light consumes the most energy in the grow room
In your typical 4ft x 4ft or 1.2m x 1.2m tent the extract fan, circulatory fan and water or air pumps will consume between 15 to 30 watts each or about 70 watts in total.
The grow light wattage required to delivery a good yield will range from 400 to 650 watts, depending on the technology used. Therefore the power consumed by your grow light is about 80-90% of the total used in the grow room (excluding air conditioning).
The cost of electricity varies in different countries and states so we use the average in the US and Europe to calculate the running cost of grow light types. The energy consumed by each grow light technology is calculated based on delivering an average PAR of 800 µmols/m²/second over a 4 x 4 grow area.
Calculating the cost of running a grow light
It is easy to calculate the cost of running your grow light with the multiplication of three inputs.
Determine grow light wattage
The first task is to determine the consumed wattage of your grow light (this maybe different than the specified wattage which can refer to LED capacity rather than consumed watts). You should be able to get the approximate consumed wattage from the manufacturers data sheet or by using a power meter.
Divide the wattage by 1,000 to get Kilowatts (kw)
For example: Grow light is specified as 500 watts. Divide by 1,000 or 500/1,000 = 0.5 Kilowatt (kw)
Determine the running time and period
Calculate the amount of hours the grow light is operating in the month.
For example: 12 hours per day x 30 days = 360 hours per month
Use the cost per KW hours from your electricity supplier
Check your most recent bill or contact your supplier to determine the hourly rate per KW hour.
For example the average cost per Kw hour in the US is 16.8c or $0.0168
Cost of electricity to run the grow light for 1 month = 0.5 x 360 x 0.168 = $30.24 per month.
You can also use an online electricity calculator like this one: Electricity calculator
Comparison of the running costs for HID and LED grow lights in the US and EU
LED grow lights are the most efficient on the market. If you are not using modern LED grow lights produced since about 2020 than you can save running costs by upgrading to high efficiency modern LED fixtures. The cost of running grow lights of different technologies is compared below.
The most efficient grow light, the modern LED grow light is on the top row. The right hand column displays the extra money you have to spend each year on electricity at todays rate.
Grow Light Running Cost 4x4
US Average 17c/KW hour
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| Make | Watts | Fixture Price |
Usable PPF*/ Watt |
Usable PPF* output | 1 year** electricity cost/4x4 | Extra electricity cost |
| LED high efficiency | 500 | $500.00 | 2.3 | 1150 | $466.18 | $0.00 |
| Low efficiency LED (pre 2020) | 500 | N/A | 1.8 | 900 | $595.68 | $129.50 |
| Metal Halide Digital | 630 | $150.00 | 0.9 | 567 | $1,191.36 | $725.18 |
| DE HPS Digital | 630 | $150.00 | 1.4 | 882 | $765.87 | $299.69 |
| MH and HPS combined | 630 | $150.00 | 1.15 | 725 | $932.37 | $466.18 |
| CMH Digital 630W | 630 | $400.00 | 1.35 | 851 | $794.24 | $328.06 |
| * Usable PPF is the amount of PAR light reaching the plant canopy in a system test with reflective walls | ||||||
| ** 1 year electricity cost to deliver 800µmols/sec usable PPF over a 4x4 for 15 hours per day at 17c per Kw hour | ||||||
Grow Light Running Cost 4x4
Euro Average 25c/KW hour
|
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| Make | Watts | Price |
Usable PPF*/ Watt |
Usable PPF* output | 1 year** electricity cost/4x4 | Extra electricity cost |
| LED high efficiency | 500 | €500.00 | 2.3 | 1150 | €685.57 | €0.00 |
| Low efficiency LED (pre 2020) | 500 | N/A | 1.8 | 900 | €876.00 | €190.43 |
| Metal Halide Digital | 630 | €150.00 | 0.9 | 567 | €1,752.00 | €1,066.43 |
| DE HPS Digital | 630 | €150.00 | 1.3 | 819 | €1,212.92 | €527.36 |
| MH and HPS combined | 630 | €150.00 | 1.1 | 693 | €1,433.45 | €747.89 |
| CMH Digital 630W | 630 | €400.00 | 1.35 | 851 | €1,168.00 | €482.43 |
| * Usable PPF is the amount of PAR light reaching the plant canopy in a system test with reflective walls | ||||||
| ** 1 year electricity cost to deliver 800µmols/sec usable PPF over a 4x4 for 14 hours per day at 25c per Kw hour | ||||||
LED grow lights are much cheaper to run than HID grow lights
It now takes just 18 months to recover the cost of purchasing an efficient LED grow light compared to a Metal Halide and High Pressure Sodium system. The savings will be even greater if you count the replacement cost of bulbs and air conditioning of the additional heat produced by HID systems.
Guide to upgrading from HPS to LED grow lights
It takes longer to recover the money if you are upgrading from an LED grow light purchased in the last few years i.e. before about 2020 but it is still worth it.
Link to US electricity cost per state: https://www.bls.gov/regions/midwest/data/averageenergyprices_selectedareas_table.htm
Link to European electricity cost per state: https://ec.europa.eu/eurostat/cache/infographs/energy_prices/enprices.html?geos=&product=6000&consumer=HOUSEHOLD&consoms=4161903&unit=KWH&taxs=I_TAX,X_TAX,X_VAT&nrg_prc=NETC,NRG_SUP,OTH,TAX_CAP,TAX_ENV,TAX_NUC,TAX_RNW,VAT¤cy=EUR&language=EN&detail=0&component=0&order=DESC&dataset=nrg_pc_204&time=2021S2&modalOption=0&chartOption=0&precision=1&modalOpen=0&modal=0&modalLineOption=0
