Ind. Admin. Code tit. 170, r. 4-1-9 – Accuracy of meters

Sec. 9. (a) No watthour meter that registers at no load (the moving element making more than one (1) complete revolution when at "no load"), when the applied voltage is less than one hundred ten percent (110%) of standard service voltage, shall be placed in service or allowed to remain in service in such condition.

(b) No meter shall be placed in service or allowed to remain in service that is in any way mechanically defective, has incorrect constants, or has not been tested for accuracy of measurements and adjusted, if necessary, to meet the following requirements:

(1) For watthour meters, the following:
1. (A) Average error not over two percent (2%), plus or minus.
2. (B) Error at full load not over one percent (1%), plus or minus.
3. (C) Error at light load not over three percent (3%), plus or minus.
(2) For curve drawing instruments, the electrical element error shall not exceed two percent (2%), plus or minus, of full scale indication.
(3) For integrating demand meters, the following:
1. (A) Electric element errors shall not exceed the limits specified for watthour meters.
2. (B) For timing element, a cumulative error shall not be in excess of plus or minus two percent (2%) for the entire billing period. If the time of day is a factor in the rate schedule, the timing element, when operating under normal conditions of service, shall not indicate a difference of more than ten (10) minutes from correct time, and any incorrect indication of time caused by the temporary loss of utility service shall be corrected by the utility by the end of the following work day.
(4) For lagged demand meters, the following:
1. (A) For electromagnetic type, the error shall not exceed two percent (2%), plus or minus, of full scale indication.
2. (B) For thermal type, the error shall not exceed four percent (4%), plus or minus, of full scale indication.
(5) Watthour meters, except self-contained meters, which are to be used on circuits supplying inductive load, shall also be tested before installation at one hundred percent (100%) of manufacturer's rated test current at fifty percent (50%) lagging power factor, and, if necessary, adjusted so that the error under such conditions will not be more than two percent (2%), plus or minus. All new meters may be tested by a meter manufacturer if certified tests are supplied.

(c) Where instrument transformers are used for metering, the ratio of transformation and phase angle error of the transformers must be determined before installation, such information being on file in the office of the public utility.

(Indiana Utility Regulatory Commission; No. 33629: Standards of Service For Electrical Utilities Rule 9; filed Mar 10, 1976, 9:10 a.m.: Rules and Regs. 1977, p. 341; 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)