A meter's registers are defined in respect of an effective-dated meter configuration. When you reconfigure a meter's registers, you add a new configuration with an effective date equal to the reconfiguration date. Whenever you add a configuration, you must specify how all of the registers look on the configuration date; you don't just specify those registers that have changed.

Every meter must have at least one configuration, otherwise the system doesn't know what it measures and meter reads cannot be specified for the meter. A meter without meter reads cannot be billed (or linked to a service agreement!).

A meter configuration has one or more registers. The number is dependent on how many things are measured. For example, if you have a meter that measures kilowatt-hours and kilovolt-amperes, its configuration will have two registers.