Deep-Dimming Fluorescent Ballasts


Deep dimming fluorescent ballasts allow lamps to be dimmed below 50% of output. They apply to ballasts that operate T5 and T8 four-foot linear and u-shape fluorescent lamps


Though there are national standards for dimming fluorescent ballasts, there are none for deep-dimming fluorescent ballasts. In 2015, the California Energy Commission (CEC) adopted the following standards for deep-dimming fluorescent ballasts:

(1)   Shall not consume more than 1 watt in standby mode;
(2)   Shall have a power factor of 0.9 or greater; and
(3)   Shall have a weighted ballast luminous efficacy greater than or equal to the threshold described in the following equation:

ballast efficiency formula

CEC also modified the national test procedure by adding criteria with which to test ballasts dimmed more than 50%.

The CEC standards took effect July 1, 2016.


CEC estimates lifetime savings of $22 per ballast over the 13-year lifetime. In California, the net present value is estimated at $38 million the first year and $505 million per year once the stock turns over.


Federal Date States
2016 CA Standard Effective
2015 CA Standard Adopted

Timeline reflects state standards from 2001 to present; federal standards from inception to present.