On your electric bill one can find the number of ``kilowatt-hours'' of electricity that has been used in a month - this is a measure of the electrical energy that has been consumed. A kilowatt-hour (kW-hr) is defined as
According to this definition, we see that 1 kW-hr is a unit of energy, which can be expressed in Joules by multiplying the power (1000 W) by the time (1 hour = 3600 seconds) so that
Thus, for example, burning a 120 W light bulb for 100 hours will consume 120 W x ( 1 kW / 1000 W ) x 100 hr = 12 kW-hr, which is about 43 million Joules. If electricity is charged at a rate of $0.08 per kW-hr, this would cost 12 x $0.08 = $0.96. Clearly the cost of electricity would seem even more reasonable if expressed in terms of Joules.