How much does it really cost to run a grow light? Electrical costs are one feature of growing your own that can be surprising to many new growers.

This chart examines the costs of purchasing grow lights as well as maintaining and powering them for 5 years. Electricity costs were calculated for 12 hours of grow light use per day. Electricity price data gathered from NPR’s breakdown of US electricity costs (data from Energy Information Administration) and the European Commision’s Eurostat (table 1). XE was used to convert Euros into US Dollars for the chart, at the time 1 Euro rounded to USD $1.29. Initial costs of grow lights are about average and may vary significantly depending on model, especially for LEDs. Wattage will also vary for each LED grow light, so this chart includes values that are about average.

I used to tell people that LED grow lights were for those that could afford them, but looking at the data I see that it’s much cheaper to shell out for a nice LED than it is to run an HID for a long period of time. If you grow short plants, you should definitely try LEDs. For tall plants, there is still no LED (in my opinion) that emits intense enough light to compete with a 1,000 watt HID.

The first series of costs on the chart represents an electricity cost of $0.12/kwH, or 12 cents per kilowatt hour (a kilowatt hour is 1,000 watts being used for one hour). $0.12/kwH was the US national average cost for electricity in 2011. At this price, LED lights become more cost-effective than their HID counterparts after 3 (for the 180 watt) or 4 years of use. The second series of costs on the chart represents an electricity cost of $0.18/kwH, which was the 2011 average cost for both New York state and the UK. At this price, LED lights become more cost-effective than their HID counterparts after 2 (180 watt) or 3 years of use. The third series of costs on the chart represents an electricity cost of $0.23/kwH, which was the 2011 average cost for the EU, converted to USD for comparison. At this price, LED lights become more cost-effective than their HID counterparts after 2 years of use.

When you see an LED grow light with a $500 – $1,500 price tag, it’s hard to believe that the savings in energy can really offset the initial cost, but it does.

Depending on your electricity prices, a 400 watt HID will cost $200 – $400 each year of use, plus the cost of replacement bulbs. LEDs meant to replace 400w HIDs average around 180 watts. A 180 watt LED will cost $90 – $180 each year of use, saving $110 – $220 over a 400 watt HID in annual electric costs with no need for replacement bulbs. Replacing a 400 watt HID with a 180 watt LED will pay off after 2 or 3 years, assuming the initial cost of the LED is around $650. Prices on high quality 180 watt LED grow lights range from under $300 – $900.

Depending on your electricity prices, a 600 watt HID will cost $300 – $600 each year of use, plus the cost of replacement bulbs. LEDs meant to replace 600w HIDs average around 300 watts. A 300 watt LED will cost $150 – $300 each year of use, saving $150 – $300 over a 600 watt HID in annual electric costs with no need for replacement bulbs. Replacing a 600 watt HID with a 300 watt LED will pay off after 2 to 4 years, assuming the initial cost of the LED is around $950. Prices on high quality 300 watt LED grow lights range from $600 – $1,300.

Depending on your electricity prices, a 1,000 watt HID will cost $500 – $1,000 each year of use, plus the cost of replacement bulbs. I still do not believe that any current LED can really replace a 1000w HID when it comes to penetration, which is necessary if growing tall (5′ and taller) plants. The LEDs that claim to replace 1000w lamps average around 500 watts. A 500 watt LED will cost $250 – $500 each year of use, saving $250 – $500 in annual electric costs with no need for replacement bulbs. Replacing a 1,000 watt HID with a 500 watt LED would pay off after 2 to 4 years, assuming the initial cost of the LED is around $1,500. Prices on high quality 500 watt LED grow lights range from $1,150 – $2,000 .

I’ve been a big fan of LED grow lights since they began using 3-watt diodes, but after seeing how much cheaper they are to run than a comparable HID grow light I’m just blown away.

Again, I do not believe that any LED grow light can really replace a 1,000 watt HID for growing really large plants. If you have a personal garden or even a large Sea of Green setup, try replacing an HID with an LED. You’ll save money in the long run, and your garden will run cooler. Just make sure to do a little research, get high-quality 3-watt diodes, a good warranty and a 90-day money-back guarantee.

There are two brand new models (130 and 330 watts) from Advanced LED Lights (a long-time manufacturer with a great reputation) that feature 10 watt white diodes between clusters of the 3 watt, 11 band diodes. I haven’t had the pleasure of trying them out, but I’m sure they’re fantastic.