GCSE Physics

New Technology: LED Bulb Payback Times

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Not everyone is interested in just saving energy - many want to know they will save enough money to pay for their investment! At around £16 each, these dimmable LED bulbs are not cheap, but the price will inevitably come down as the technology is developed.

Data for 8 BulbsHalogenDimmable LED
Power (W)40042
Power (kW)0.400.042
Daily Use (h)22
Daily Energy Use (kWh)0.800.084
Annual Energy Use (kWh)29230.7
Annual Energy Cost ()40.884.30

The bottom row of the table shows that the energy saved in a year would pay for over 2 of the LED lamps! But let's do some more precise calculations. Grab a pen, some paper and a calculator and then answer these questions. Check your answers at the end, or click for hints!

  1. What is the cost of 8 LED lamps for the kitchen example above?
  2. How much money is saved per year if they're used for 2 hours a day on average?
  3. Calculate the payback time, in years, for buying 8 lamps, used for 2 hours a day.
  4. Totalight's website suggests an LED lamp "pays for itself in 18 months". How many hours would the kitchen LED lamps have to be used for a payback time of 18 months?
  5. Explain whether or not a payback time of less than 18 months would be achievable in a school or office using LEDs instead of halogens.


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