Cost of Operating a Fluorescent Light Fixture

Comparing Costs

• You measure the amount of electricity a light bulb uses in watts and the amount of light it produces in lumens. You measure the efficacy of a light, sometimes called lumens per watt, by dividing lumens by watts. The exact cost per watt depends on the electricity rates in your area, but you can compare the efficacy of different lights to determine which is more efficient.

Calculating Costs

• If you know the kilowatt-hour price of electricity, you can calculate the exact cost of operating a fluorescent light. Determine the watts used per day by multiplying the watts of a light by the average number of hours the light is on per day. Then multiply by 365 and divide by 1,000 to find the yearly kilowatt usage. Multiply by the cost per kilowatt-hour to determine your annual cost of operating a bulb. For example, suppose you use a 28-watt light for five hours a day. That equals 140 watts per day and 51,100 watts per year, which is equivalent to 51.1 kilowatts. If a kilowatt-hour costs 12 cents, the light costs about $6.13 annually.

Additional Costs

• Fluorescent lights cost more than incandescent lights to purchase, although the saving in electricity costs usually more than makes up for this extra cost. In addition, because fluorescent lights contain small amounts of mercury, you must recycle fluorescent lights instead of throwing them away; this may take extra time. Finally, incandescent lights have slightly better color rendition than fluorescent lights, which may decrease the value of fluorescent lights for some people.

Additional Savings

• Fluorescent lights last about 10 times longer than incandescent lights, so you won't have to spend time and money installing and buying new lights. Fluorescent lights also give off much less heat than incandescent lights, which produce more than 90 percent of energy as heat, so using fluorescent lights lowers your air conditioning bill. Finally, using less electricity also reduces your burden on the environment.