Investigating Costs of Energy Sources

Section 1 of 7Fuels 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.

Section 2 of 7How mains gas and electricity are charged

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.

Section 3 of 7Comparing fuels

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

Section 4 of 7Making the comparison

1

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

2

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.

3

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

4

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

5

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

Section 5 of 7Reading the data

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.

Section 6 of 7Key terms

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.

Section 7 of 7Exam technique

1

Ignoring the standing charge when working out a total bill.

2

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

3

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

4

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