Question by Mani: URGENT SCIENCE PHYSICS QUESTIONS! 10 POINTS for explanation ?
A normal 100W light bulb costs about 50p and lasts for 1000 hours.

An ‘energy-saving’ bulb only uses about 18W to produce the same amount of light. It costs £5.95, but it will last for 6000 hours (100W=0.1kW, and 18W = 0.018kW)

How much money would you save overall by using an energy-saving light bulb if electricity costs 7p per Unit (kW)

- This question is very difficult because it is very confusing. As my answer, I got the normal bulb saving more money, but the question asks how the energy-saving bulb could save you. VERY CONFUSED!

If you know the answer, please explain how you got it, and you will get 10 points and get the ‘best answer’ status. Thank You in advance!

Using a 60 watt light bulb for one thousand hours consumes 60 kilowatt hours of electricity.

One energy saving bulb goes for 6000hrs at 18W for a cost of
£5.95

plus energy
7p X 18 X 6
=£7.56

Total
£13.51

By contrast…

Six normal 100W bulbs cost £0.50 X 6 = £3.00
plus energy
7p X 100 X 6
= £42.00

Total
£45.00

It is cheaper and greener to use a single (long life) energy saving bulb, rather than 6 normal bulbs.

You would save … well … you work it out.

Then for extra credit you could mention that you save money disposing of one energy saving bulb instead of 6 normal bulbs, transport and shipping costs, storage and handling, etc.