GCSE Physics

New Technology: LED Bulb Savings

How Science Works

So how much money can be saved using LED bulbs? As always, it depends on how you use lights. You should know that the cost of electrical energy depends on:

  • The power, P of the device (in watts, W or kilowatts, kW)
  • The time, t it is turned on for (in seconds or hours)

    Energy = Power × Time will give you the energy use in joules or kilowatt-hours (kWh).

    Let's look at a typical modern kitchen as an example, with eight 50 W halogen lamps used for a time roughly averaged over a year:

    Data for 8 LampsHalogenDimmable 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

    [Cost based on 1 kWh of electrical energy costing 14p. This price is very likely to rise into the future.]

    So with a daily average use of 2 hours only for 8 lamps, the total energy saving is considerable and the associated cost saving very significant.


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