For calculating the cost of used electricity, using single-rate meter, from the figures of meter readings on the day of payment, subtract the previous number, which is specified in the receipt on the day of payment. Multiply the resulting difference by the amount of the tariff in your region. The result will be worth spent for electricity in a given month.
When calculating the cost of used electricity for two-tariff meter must be read at two rates. Rate the night time, which is valid in your region and day. From the meter to the night rate, subtract the figure in the column on the payment date in the previous receipts. Also do with the testimony of the daily rate. The amount received multiply by a night and day tariff, both amounts will add up. You have used the cost of electricity, you need to pay.
Using multi-rate metering device is necessary to consider all the numbers and amounts for each time and rate separately, add up all the amounts and to pay the consumed electricity.