These ballasts have an average life of 45,000-50,000 hours. When the bulb needs to be replaced, the entire unit must be replaced. However, these bulbs last about 10 time longer than standard incandescent bulbs.
Circline bulbs are fluorescent tubes in the shape of a circle.
They can be screwed in to replace incandescent bulbs, and can be plugged into a reusable ballast or purchased as a one-piece unit. The following table lists several standard incandescent bulbs and the compact fluorescents that can replace them. This comparison is an approximation. The actual lumens or light output may vary from bulb to bulb. Although compact fluorescent bulbs initially cost more than incandescent bulbs, they can use less energy and last longer.