Ind. Admin. Code tit. 170, r. 4-1-8 – Average accuracy of watthour meters; tests

Sec. 8. (a) The accuracy at light load shall be determined at a load of approximately ten percent (10%) of the rated test amperes of the meter. The accuracy at full load shall be determined at a load of one hundred percent (100%) of the rated test amperes of the meter. For meters used with current transformers:

(1) full load shall be approximately one hundred percent (100%) of either the meter test amperes or the secondary current rating of the current transformers; and
(2) light load shall be approximately ten percent (10%) of the selected full load current.

Average percentage registration is the average of the percentage registration at light load (LL) and at full load (FL). Thus, average percentage accuracy = (FL + LL) ÷ 2.

(b) The accuracy at light load shall be determined by taking the average of at least two (2) tests, which tests must agree within one-half of one percent (.5%) unless the meter has been tested by an automated device in which case one (1) test will be sufficient. The accuracy at full load shall be determined in a like manner. The average accuracy of the meter shall be determined by taking an average of the accuracy at light load and of the accuracy at full load. However, the average "as found" accuracy of a meter may be determined from one (1) light load test and one (1) full load test if:

(1) such average accuracy is less than one hundred three percent (103%); and
(2) if such meter is to be adjusted.

(c) After any meter has been adjusted, the "as left" accuracy of the meter shall be determined by tests at each load as outlined in subsection (b).

(Indiana Utility Regulatory Commission; No. 33629: Standards of Service For Electrical Utilities Rule 8; filed Mar 10, 1976, 9:10 a.m.: Rules and Regs. 1977, p. 340; filed Feb 23, 1998, 11:30 a.m.: 21 IR 2323; readopted filed Jul 11, 2001, 4:30 p.m.: 24 IR 4233; readopted filed Apr 24, 2007, 8:21 a.m.: 20070509-IR-170070147RFA; readopted filed Aug 2, 2013, 2:16 p.m.: 20130828-IR-170130227RFA; readopted filed Apr 11, 2019, 9:04 a.m.: 20190508-IR-170190136RFA; readopted filed Sep 12, 2025, 11:43 a.m.: 20251001-IR-170240381RFA)