All commercial energy registers are accumulative which means that the previous reading is subtracted from the present reading and the difference is the amount used during the billing period. The meters measure the energy consumed in kilowatt hours (Kwhs). There are two types of demand registers known as needle type and accumulative type.
- The needle type demand register displays the recorded demand using a pointer on a graduated scale, or on dials (read right to left), or on a digital LCD readout. The needle type demand register is always reset to zero (0) to begin the next reading cycle.
- The accumulative type demand register displays the recorded demand on dials or a digital readout and is reset prior to taking the reading.
As with the energy register, the amount of recorded demand is the difference between the present reading and the prior reading.
There are basically three methods of acquiring meter readings:
- Physically reading meter dials (from right to left),
- Physically reading a digital register, or
- Downloading meter readings via computer telecommunications.
The first two methods require a meter reader, of course, and, therefore, are more prone to human error, but the hand-held recording devices they use are programmed to alert the meter reader if the reading entered does not fall within certain parameters and he must double-check the reading. The hand-held computer will not allow the meter reader to move on to the next meter reading until the parameters are satisfied or overridden, keeping reading errors to a minimum.
The last method of downloading the meter readings over a phone line (or dedicated line) are digitally transferred and the readings are error-free. This last method is basically infallible of recording an erroneous reading.