Oscilloscopes measure current and voltage and, through the magic of mathematics, calculate power. Unfortunately, power comes in a large number of guises: instantaneous, real, apparent, and reactive.

Cost = power (in kWh) × time (in hours) × price of 1kWh on your energy tariff. (A kilowatt hour or kWh is calculated by dividing the wattage by 1,000.) So, let’s say, for example, you have an electric ...