Compact fluorescent light (CFL) bulbs have been avaiable for years; they are bery efficient but a little pricey. A CFL bulb that puts out as much light as a 60-W incandescent bulb might costs $10, compared to about $1 for the incandescent bulb. But CFL bulbs are expected to last (on average) 15,00 hours, compared to about 1000 hours for an incandescent bulb. so it is easy to say that you would meed 15 incandescent bulbs (total cost $15) to last the 15,000 hours that you would get from one ($10) CFL bulb; you save $5 and a lot of climbing ladders to replace all those incandescent bulbs.
But theres more. A CFL bulb that puts out as much light as a 60-W incandescent bulb will use about 13W or power. according to the US Energy Information Administration, residential electricity costs average about $0.10 per kilowatt/hour (1kQ/h=3600 kW/s=3600 kJ). Over the 15,000 hours that one CFL bulb is expected to last, how much will you save on power if you replace an incandescent bulb in your home with a CFL bulb.
Find the Total energy cost and savings from using both CFL bulbs and incandescent bulbs.