How much does it cost to run my plant lights?
Growing plants under light? Find out how much it’s really costing you and whether it’s worth it or not.
December 17, 2012 - Author: Gary Heilig, Michigan State University Extension
Growing plants indoors is fun and therapeutic, especially during Michigan’s dark, winter days. Forcing bulbs, starting seedlings, blooming African violets or orchids, or just growing foliage plants that clean the air is a welcomed alternative to staring out a window viewing the magnificent desolation of the season.
In order to produce and keep good quality plants, supplemental lighting is usually required. Utility costs are really up and some people might be a bit concerned about the extra expense that plant lights will add to the monthly bill. Michigan State University Extension will share with you how to calculate those costs and help you to determine whether or not it is worth it.
The first thing that we will look at is the rate paid for electricity. This can be found on your bill and is expressed in cents per kWhr (kilowatt hour). For example, my basic energy charge is $0.079797/kWhr, but there is more. Added to the basic rate is a PSCR renewable energy, system access distribution, energy efficiency and securization charges plus a securization tax, which brings the rate up to $0.122109/kWhr.
The next thing I need to know is some information on the light fixtures, specifically the wattage of the bulbs. Let’s say that I am using two, 4-foot fluorescent fixtures that contain two 40 watt grow lights each. The total wattage is 160 (four bulbs x 40 watts). Since we are charged using kilowatts, divide 160 by 1,000 and multiple by the rate, which for me would be $0.122109/kWhr = $0.0195374. The result is the cost to run the lights for one hour. Multiply $0.0195374 by the number of hours you plan to run the lights (14 hours). The cost to run the lights per day is $0.2735236 or $8.20 per month.
If I have an HID (high intensity discharge) light with a 600 watt bulb in it, using the same method of calculation, it would cost me $30.90 per month. Of course, with a metal halide HID light I could grow my own tomatoes and other vegetables indoors. Is it worth it? You decide!