Watt hour meter (Three Phase Smart Card Meter) is a kind of watt hour meter, which measures the electric energy consumed by the house in kilowatt hours. The meter has a counter in kilowatt hours. The energy consumption is calculated by calculating the reading difference of the counter in a specified period of time. Using a watt hour meter for metering can provide a key window into your energy consumption and ultimately your energy bill. Users can accurately monitor energy use in real time, rather than waiting until the end of the billing cycle.