(1) Electric utilities must maintain in reasonable working order all portable indicating electrical instruments used to determine quality of electrical service, such as volt meters, ammeters, and watt meters, and all fixed-location meter testing equipment in use and, if in question, must check it against suitable reference standards. If suitable reference standards are not available within the utility, the utility must check its portable instruments at a standardizing laboratory meeting specifications recommended by the meter manufacturer.

(2) Electric utilities must adjust portable analog indicating instruments that are found appreciably in error at zero. If a portable analog indicating instrument is in error by more than one percent at commonly used scale deflections, the electric utility must adjust it, unless the instrument is accompanied by a calibration card.

(3) Electrical utilities must maintain in good working order, as specified by the manufacturer of such instruments, all portable indicating electrical instruments used for purposes other than determining the quality of electrical service, such as instruments primarily for the safety of workers.

(4) Electric utilities must keep history and calibration records for each portable indicating electrical instrument used to determine quality of electrical service as defined in subsection (1) of this section, as long as the instrument is in service.