This helpful article from Low Cost Living tells you why you should change to using low-energy lightbulbs. They may cost more to buy up front, but the electricity you save will more than make up for this.
I find it quite amazing that some people still use old fashioned incandescent light bulbs when modern compact fluorescent lamps as low energy bulbs are properly called, are so much cheaper to run even if they are a bit more expensive to buy.
In fact you will often find that energy companies are giving away these bulbs to promote energy saving.
The old bulbs used to be slow to warm up and give the same light output as their rating but the technology has improved tremendously.
The lifespan of a low energy bulb is between 8 and 20 times that of an old fashioned bulb which lasted just 1,000 hours, and they are available in a huge range of sizes. nearly anything you used an old bulb for can take a new bulb.
The big saving comes in the electricity cost.
Now let's calculate the savings you can make with one light bulb. A 20 watt low energy bulb will save, over its 20,000 hour life some 1,600 Kwh of electricity. At today's rates of 12p per Kwh that is some £192.00! Oh, and don't forget you would have had to buy some 20 old incandescent bulbs.
Even lower wattage special conventional bulbs can be effectively replaced. A 60W PAR kitchen spotlight bulb can be replaced for about £3.50 with an 8,000 hour PAR. Plugging in the figures as for the 100 W bulb shows that we save £47.04 on power and the bulbs are cheaper too as we only need one low energy bulb at £3.50 against 8 conventional at £2.00 each
You can even get a bulb you can use with a dimmer switch now - there's more information on these at Nigel's eco-store, he specializes in the greener side of life
If you think a special bulb will be expensive, just do the maths as I have above and check for yourself.