1.3.6Electricity, Energy and Waves

Investigating Costs of Energy Sources — WJEC GCSE Science (Double Award) - Physics Revision Notes & Topical Questions

5 min read 7 parts Lesson 21 of 36

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Part 1 of 5Fuels used in the home and on the road

Heating homes

Heating homes Homes can be heated by gas boilers, electric heaters, oil or biofuel central heating, log burners, bottled gas heaters and bio-ethanol fires.
Natural gas central heating is the most common system in the UK.

Powering vehicles

Powering vehicles Cars and vans run on petrol, diesel, electricity or biofuels.
Fuel sold in the UK has some biofuel mixed in to reduce carbon dioxide emissions.

Price changes

Price changes Petrol and diesel prices change from day to day with the world price and supply of crude oil, national supply and demand, and taxes.

Energy bill

Unit price

Unit price Gas and electricity are charged per kilowatt-hour (kWh) used, and electricity costs more per kWh than gas.

Standing charge

Standing charge A fixed daily amount that pays for being connected to the supply, charged even when little energy is used.
Typical figures are about 30 p per day for gas and about 55 p per day for electricity.

Bottled gas

Bottled gas Propane and butane are bought in bottles, so there is an initial cost for the empty bottle and then a lower cost for each refill.

Fuel	Cost per unit	Unit	Energy per unit (kWh)	CO₂ (kg per kWh)
Gas	7.4 p	kWh	1.0	0.2
Electricity	28.6 p	kWh	1.0	0.5
Wood	about 24.8 p per kWh of fuel	kg	4.2	0.003
Coal	about 1.7 p per kWh of fuel	kg	6.9	0.4
Oil	about 7.3 p per kWh of fuel	litre	10.4	0.3
Bio-ethanol (crops)	about 53.8 p per kWh of fuel	litre	6.5	0.1

Find the price for one unit of the fuel and the energy it contains in kWh.

Divide the price per unit by the energy per unit to get the cost per kWh, so different fuels can be compared on the same basis.

Multiply the energy needed by the cost per kWh, and add any standing charge for the period.

Compare the carbon dioxide released per kWh to judge the environmental impact as well as the cost.

State a conclusion that balances cost against emissions, for example wood has very low emissions but needs storage and handling.

Cheapest per kWh

Cheapest per kWh Mains gas is much cheaper per kWh than mains electricity, which explains why gas heating is so common.

Emissions

Emissions Electricity shows high emissions per kWh at the point of use in the data,
- while wood and biofuels show lower values because the plants absorbed carbon dioxide while growing.

Term	Meaning
Standing charge	A fixed daily charge for being connected to the gas or electricity supply.
Kilowatt-hour (kWh)	The unit of energy used by suppliers to charge for gas and electricity.
Biofuel	A fuel made from plant or animal material, such as bio-ethanol.
Tariff	A supplier's price plan, including unit prices and standing charges.
Carbon dioxide emission	The mass of carbon dioxide released when a fuel is used.

Ignoring the standing charge when working out a total bill.

Comparing fuels using the cost per litre or kg without converting to cost per kWh.

Mixing pence and pounds; divide by 100 to change pence to pounds.

Considering only cost and forgetting emissions when asked to evaluate a fuel.

Last updated: 20 October 2026