In the area of power metering, especially in some regions, the following trend is obvious these days: Utilities require a more sophisticated payment infrastructure to facilitate the payment process for energy. This process also reflects the recent trends in improving the security in these systems, including theft prevention. There is an appreciable trend to transition from a fixed-rate billing to a time-of-use billing. Secure prepaid meters may be used for this purpose. These types of electricity meters give the customer a greater control over their electricity bills. The target regions for using the prepaid meters are mainly the UK, Eastern Europe, Latin America, South Africa and Asia. These types of meters are suitable for installation in landlords' flats, in shops, stores and sporting facilities, etc.
The basic and common principle of prepayment in energy meters is to buy energy credit in advance and to inform the prepaid meter in some manner. This means that customers decide how much energy they need and want to consume. This solution gives the customer greater control over their energy usage. After the prepaid amount of electricity is consumed, the user is automatically disconnected from the mains unless he/she makes a further prepayment for electricity. This is the main difference in comparison to traditional power meters (based on fixed-rate billing transactions), where the customer consumes electricity continuously.
For the prepaid metering market, there is the need to build that payment infrastructure. Generally, a bank account, an ATM, vending stations or shops are required to reload the energy credit. The main parts of the typical prepaid meter are: the metering part that measures the accumulated energy, a contactor used for disconnecting the meter (consumer) from the mains, and a prepaid sensing element which is used for loading the energy balance onto the meter itself. According to the prepaid sensing element, we may differentiate several types of prepaid meter solutions:
• Based on an electromechanical system – prepayment is done simply by coins
• Using a meter’s integrated keypad – users buy energy credit at the vendor company which generates a unique PIN which is assigned to the meter through the keypad
• Using a token - plastic key or magnetic strip card (may be obtained from a vending machine)
• Using a memory card which is refreshed at a vending station and finally put into the prepaid meter by the user
• Using a smart card which offers the same behavior as memory cards, but with improved security (mutual authentication, etc.) - these smart cards may be contact or contactless
• Wirelessly (using a mobile phone) – mostly based on GPRS, ZigBee or NFC communication - these technologies may be used not only for loading the energy balance, but also for wirelessly reading the smart meters’ data or valuable information by authorized utilities in real-time