Electronic ballasts operate fluorescent lamps more efficiently at frequencies greater than 20,000 Hz. The increase in lamp efficacy, combined with reduced ballast losses boosts fluorescent efficacy by up to 30 percent. Normal-output electronic ballasts are generally rated with a ballast factor of .90. Ballast factor is simply the percentage of the lamps rated lumens produced by the specified lamp-ballast combination. This approach, called tandem wiring, requires fewer ballasts and is more efficient.
Electronic ballasts are available in a wide range of ballast factors.
Partial-output electronic ballasts can reduce electricity consumption where reduced illumination is acceptable. The following are typical ranges of THD for each ballast type. THD Harmonic distortion is also caused by many other types of electronic devices such as fax machines, printers, computers, and copy machines.