GCSE SCIENCE PHYSICS HIGH SCHOOL - Mains Electricity - Bills

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Mains Electricity - Bills.

If you look at a domestic electricity bill,
you will see that there are two meter readings.
One is the present reading and the other is the previous (last) reading.
Subtracting the previous reading from the present one
gives the number of units used in that 3 Month period.

Electricity is priced in pence per unit.
Multiplying the number of units used by the price per unit
gives the cost of electricity for that period.
Other costs may then be added, such as the
standing charge (which must be paid no matter how much electricity you use,
for the convenience of being connected),
and VAT which is a tax collected by the government.

One unit of electricity is 1kWh (one kilowatt-hour),
kilo means thousand, so one kilowatt-hour is
the amount of electricity used by a 1000W appliance running for 1 hour.

1 Watt is 1 Joule per second, 1000W = 1000J per s.
1 hour = 60 x 60 seconds, = 3600 seconds.
Therefore, 1kWh = 1000 x 3600 Joules,
= 3,600,000 Joules of energy.

Note that a kWh is a unit of energy, not power.

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