Investigating the Cost of Using Appliances
- Two appliances that have the same function may not always cost the same to run
- On most appliances, manufacturers provide energy rating labels to allow customers to make comparisons
- Energy rating labels describe:
- The energy consumption of the appliance in kWh per year
- The efficiency of the appliance by assigning a band value from A to G, where A is the most efficient and G is the least efficient
- Note: In the 2010s, additional bands A+, A++ and A+++ were added to reflect the increased efficiencies of modern appliances, but these have been replaced by A-G
Energy Efficiency Rating Label for a Fridge
The energy rating label for a fridge tells us how efficient it is, how much energy it uses in a year, as well as additional information about its size and noise level
Comparing the Cost of Appliances
- Over the years, lightbulbs have become increasingly more efficient while generating the same amount of light
- A comparison of 4 different bulbs is shown below
| bulb | image | average lifetime | power rating (equivalent brightness) |
| light emitting diodes (LED) |  |
25 000 hours | 12 W |
| compact fluorescent (CFL) |
|
8000 hours |
15 W |
| halogen |
|
2000 hours |
42 W |
| incandescent |  |
1000 hours | 60 W |
- To work out the annual energy consumption of a lightbulb:
units of energy used (kWh) = power used (kW) × time (hours)
- To work out the annual cost of each lightbulb:
cost (£) = units of energy used (kWh) × cost per unit (£ per kWh)
- Substituting in the first expression:
cost (£) = (power used (kW) × time (hours)) × cost per unit (£ per kWh)
- In one year, there are 24 × 365 = 8760 hours
- Assuming a constant usage (24 hours a day) and a tariff of 10p, or £0.10 per kWh
- Annual cost of an LED lightbulb = 0.012 × 8760 × 0.10 = £10.51
- Annual cost of a CFL lightbulb = 0.015 × 8760 × 0.10 = £13.14
- Annual cost of a halogen lightbulb = 0.042 × 8760 × 0.10 = £36.79
- Annual cost of an incandescent lightbulb = 0.060 × 8760 × 0.10 = £52.56
- Therefore, an LED lightbulb is about 5 times cheaper to run than an incandescent bulb
Examiner Tip
In recent years, energy labels have changed to be more 'customer friendly', so you may see slightly different information on labels depending on the appliance itself, for example, TV labels now display different power ratings for 'standard definition display' and 'high definition display'
