Lighting makes up approximately 20% of the total electricity use in the US of which 15% is solely from household electricity use. The typical household still uses incandescent light bulbs, spending about $110 per year on lighting bills. Use of compact fluorescent light (CFL) can reduce this expense markedly.
CFL bulbs emit light that is a mixture of three phosphors exposed to ultraviolet light produced by mercury atoms. This process is unlike incandescent bulbs, which use filaments. Though CFLs cost more at the onset, they are tested to provide 8,000 hours of light as against the 500-2,000 hours from incandescent bulbs. This translates to about $36-45 of savings per CFL. Here is the math—an 18-watt CFL costing $15-20 saves you from purchasing ten ordinary 75-watt incandescent bulbs.