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Physics-Paying for energy
Power: amount of energy transferred per second (measured by watts)
1 unit = 1 kilowatt per hour=1 watt
Step 1: Electrical energy used (kWh) = power (kW) X time (h)
Step 2: Total cost = number of units X cost per unit
energy transferred (kWh) = power (kW) × time (h)
Note that power is measured in kilowatts here instead of the more usual watts. To convert from W to
kW you must divide by 1000.
For example, 2000W = 2000 ÷ 1000 = 2kW.
Also note that time is measured in hours here, instead of the more usual seconds. To convert from
seconds to hours you must divide by 3600.
For example, 1800s = 1800 ÷ 3600 = 0.5 hours.