The cost of electricity is based on which metric?

• A. Reactive power
• B. Wattage used over a period of time
• C. Daily usage hours only
• D. Peak voltage

Answer: (B)

Electricity cost is based on energy usage, typically billed in kilowatt-hours. That means the bill reflects how much power you use over time, not just a momentary power reading. Power times the time you use it gives energy (watt-hours, or kilowatt-hours). Reactive power doesn’t count toward normal residential charges because it doesn’t do useful work. Simply counting daily usage hours can be misleading, since a device’s energy use depends on both how much power it draws and how long it runs. Peak voltage isn’t the billing metric, as voltage is the potential difference, not the amount of energy consumed. So the metric is wattage used over a period of time.