Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, on lamps and light sources - energy saving lamp savings, is answered by Philips Lighting:
Answer: The formula is the same for either lamp in calculating individual costs; then just subtract one from the other to obtain the savings: (number of lamps x watts / lamp x burning hours x £ elec unit charge)/1000.
The elec unit charge is derived from the electricity bill (about 10p domestically) and should be expressed in pounds (£) for the formula (eg: £0.10). Dividing all by 1000 as shown above is to change watts into kilowatts.
Note that, as of September 1st 2009, incandescent lamps - including GLS lamps - started to be phased out. This process will be completed by 2016. Only energy saving equivalents will be available.
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