General service candelabra base lamps use a screw base commonly designated as E11 or E12 according to ANSI designation. The designation refers to the diameter of the base, in millimeters. Candelabra bases are smaller than conventional A-lamps which use a medium base (E26 or E27). Candelabra base lamps are frequently used in chandeliers, ceiling fans, and small table lamps. Intermediate base lamps, E17, are far less common than candelabra and can be found in small table lamps, novelty fixtures, and ceiling fans.
Current DOE standards, set by Congress in 2007, establish different baselines for the two lamp types with different standard levels for each.
Each intermediate base incandescent lamp shall not exceed 40 rated watts.
A DOE rulemaking is underway to update standards for these lamps. According to DOE's proposed rule, by January 1, 2020, candelabra and incandescent base incandescent lamps will need to meet a standard of 45 lumens/watts. They will likely be replaced by LEDs or CFLs.
Annual shipments are 280 million for candelabra and 29 million for intermediate base lamps.