(1) The rate schedule usage data for any cost of service study must come from the best available source: Advanced metering technology, including advanced metering infrastructure (AMI) and advanced meter reading (AMR); or, a load study.

(a) For utilities with AMI, the use of data from a load study must be explicitly justified.

(b) For utilities with AMR, data from AMR may be used if granularity of the data meets or exceeds hourly for electric and daily for natural gas. For utilities with AMR with the data granularity required by this subsection, the use of data from a load study must be explicitly justified.

(c) For utilities with other advanced metering technology, data from that metering technology may be used if granularity of the data meets or exceeds hourly for electric and daily for natural gas. For utilities with other advanced metering technology with the data granularity required by this subsection, the use of data from a load study must be explicitly justified.

(d) For utilities that do not have advanced metering technology described in subsection (1), (2), or (3) of this section, a load study must be used. Data from special contracts may be used in a load study.

(e) Street lighting schedules may be estimated and, if so, the estimation method must be explicitly presented in testimony and exhibits.

(2) Rate schedule usage data for any cost of service study must not be older than five years.