Electricity meters are devices for displaying the power consumption (energy consumption) in electrical systems. In households, AC induction meters are mainly used, which directly indicate the kilowatt hours consumed. Main component of these electricity meters is a rotating aluminum disk (Ferraris disc), where eddy currents are induced and whose magnetic fields cause rotation of the disk. The aluminum disc drives a counter mechanism that indicates the kilowatt-hours or fractions thereof. For several years, electronic electricity meters without mechanic parts have been on the market. Current standard in electronic electricity meters are digital electricity meters and so-called smart meters which measure the electric power. The power consumption is then captured depending on the time of day, usually in 15-minute intervals.