1The meter counts kilowatt-hours
Every home has a meter that counts the kilowatt-hours used. Energy companies often call a kilowatt-hour a unit. Smart meters send their readings automatically.
meterunit
Lesson 12.3 notes
Paying for energy
Meter readings, working out the cost, what a bill adds, and saving energy at home.
2Reading the meter
To find the energy used, take two readings and subtract: energy used = new reading − old reading. Here, 5001 − 4281 = 720 kWh.
3Working out the cost
cost = energy used (kWh) × price per kWh. At 25p per kWh, 720 kWh costs 720 × 25 = 18 000p, which is £180.
4What's on a bill
Prices change. In October 2026 electricity cost about 26p per kWh and gas about 8p. Bills also add a standing charge for every day, even if you use nothing.
standing charge
5The cost of running an appliance
To find what an appliance costs: change watts to kilowatts, work out energy (kWh) = power (kW) × time (h), then multiply by the price per kWh.
6Power isn't everything
A kettle has a high power but is on for only minutes a day. A fridge-freezer works day and night, so over a year it uses more energy.
7Saving energy at home
Save energy and money: use LED bulbs (the same light for about an eighth of the power), switch off standby, take shorter showers and boil only the water you need.
Explore: Running costs
Choose an appliance and how long it's on each day. See what it costs in a day and in a year.
Common mistake: A high power rating doesn't always mean a big bill
A 3 kW kettle is on for only a few minutes a day. A fridge-freezer has a much lower power, but it works day and night, so over a year it can use more energy and cost more.
Remember
- Energy used (kWh) = new meter reading − old meter reading. A kWh is often called a unit.
- cost = energy used (kWh) × price per kWh. Change W to kW and minutes to hours first.
- Save money by using lower-power appliances (like LED bulbs) and using things for less time.
Going further at GCSE
GCSE: Power and energy transfer → GCSE: Efficiency → GCSE: Insulation →