A filament lamp-
expected life- 1000 hours
a compact fluorescent lamp (CFL)-
expected life- 8000 hours
a filament lamp with a power rating of 100W gives 2000 units of light.
what power rating would a CFL need to provide 2000 units of light?
elecricity costs 15p per KWh.
what will be the cost of using a 100W filament lamp during it's expected life?
in it's lifetime, a security light is used for 15000 hours.
how much would you expect to spend on buying CFLs for the security light in that time?