A fluorescent light converts electrical energy into useful light much more efficiently than an incandescent light bulb. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with the comparable light output.
Fluorescent light fixtures are more costly than incandescent light bulbs because they require a ballast to regulate the current through the lamp, but the lower energy cost typically offsets the higher initial cost.
Because they contain mercury, most are classified as hazardous waste.