While all traditional incandescent light bulbs have the ability to dim, not all energy efficient bulbs are rated for use with a dimmer switch. ENERGY STAR requires testing on how the bulb dims to ensure it will dim if it is labeled as a dimmable bulb. CFLs labeled as dimmable only dim between 10 and 20 percent of initial light output, but LEDs generally dim very well. Look on the package to see which bulbs have this feature.
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