A Programmable Demand Register (PDR.TM.) which has a multi-function externally programmable time based measuring system is disclosed. An optical communication port is provided for bidirectional communication of data, said meter being capable of recordation of energy consumption in several different modes, according to the decision of the meter programmer. Meter programming is accomplished by means of any one of three separate devices, namely a Programmer/Reader (P/R) which is a sophisticated computerized device fully adapted to reprogram the PDR.TM. to function in any one or combination of modes as desired, to both receive and store data, and to output said data to a central billing recordation computer, and a billing period resetter (BPR) which is a battery powered device also adapted for two way communication, but limited to resetting the BPR as to data in the BPR memory, but not as to mode of operation of the BPR, and an inexpensive lightweight BPR-1 which also has two way communication capabilities, but limited to resetting the various meter functions, after insertion of a manually programmed password by the actuation of a series of switches.