Regulatory rules specify the required accuracy of meters, procedures for testing meters and procedures for the replacement of inaccurate meters. For example, most electric induction meters are typically accurate to plus or minus 0.5% over a 20-year period. All meter installations are recorded in a database so that the utility always knows the age and type of any of its meters as well as when it was last tested.
Because utilities have so many meters in the field, not all can be tested regularly. Instead, a selected sample of meters of the same type and age are periodically tested, and statistical methods are used to estimate the accuracy of the remaining meters in the field. However, if a meter read is disputed by a customer, the customer can typically request that a meter be tested by the utility.
Meter testing procedures are well-defined by meter standards organizations. Meters can be tested either in the field or in the meter shop. Testing in the field is less accurate due to wide variations in field conditions. When tested, the meter is compared to a calibrated meter known as a “standard.” If the meter being tested gives results outside of tolerances when compared to the standard, then the meter must be replaced.
All gas and electric companies require accurate meter data so that customer bills can be rendered. Diversion refers to the unauthorized use of gas or electricity; tampering refers to altering the meter so that it reads usage inaccurately. All utilities must have well-crafted procedures to identify diversion or tampering when it occurs. One advantage of using manual reads by meter readers rather than AMR is that each meter is inspected monthly when the meter reader collects the data. When a utility moves to AMR, it will typically implement a statistical review of all meter data to identify anything that appears abnormal. When such data is identified, an employee can be dispatched to inspect the customer’s meter and service conductor to determine whether diversion or tampering has occurred.