Commonwealth Edison Company, a unit of Chicago-based Exelon Corporation, says that since it began its One Million Compact Fluorescent Lights Discount Program October 1, customers have already purchased 500,000 CFLs, or about half of the supply.

Customers can order up to 12 discounted CFLs, at up to $2 off per bulb plus an additional 20 percent discount at checkout, from the ComEd Online Energy Store.

Last year, ComEd customers purchased more than 1.2 million discounted energy efficient light bulbs within six weeks, reducing their annualized electric use by about 36 million kilowatt-hours, or the amount of energy needed to annually power about 3,700 average area homes, saving an estimated $3.5 million on their electric bills this year as a result.