Abstract: A security system for programmable revenue class electricity meters. Each programmable revenue class electricity meter includes a metering portion or stage that couples to a power line. The metering portion is responsive to and senses the electricity in the power line and provides a digital output. The programmable revenue class electricity meter includes a processor that runs programming that records, calculates, and/or stores data relating to the electricity sensed by the metering portion. In particular, the programming records, calculates, and/or stores revenue-related data that can be used for calculating charges for the electricity. The programming can be changed by authorized persons to modify the types of data that can be measured, calculated, recorded, displayed, communicated, and/or stored for any desired purpose and in particular for revenue-related purposes. Modification of the programming and access to information is limited to authorized persons by means of the security system.