
New Technology: LED Bulb Payback Times
 
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 Bulbs  Halogen  Dimmable LED 

Power (W)  400  42 
Power (kW)  0.40  0.042 
Daily Use (h)  2  2 
Daily Energy Use (kWh)  0.80  0.084 
Annual Energy Use (kWh)  292  30.7 
Annual Energy Cost (£)  40.88  4.30 
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!
 What is the cost of 8 LED lamps for the kitchen example above?
 How much money is saved per year if they're used for 2 hours a day on average?
 Calculate the payback time, in years, for buying 8 lamps, used for 2 hours a day.
 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?
 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.

