At last, the truly long- lived light bulb. Called the E-Lamp (the E is short for electronic) by developer Diablo Research and licensee Intersource Technologies (both in Sunnyvale, Calif.), the bulb survives some 20,000 hours -- 20 times as long as today's most durable 100-watt incandescent, whose output it approximates. The E-Lamp is expected in stores by June at a price of around $15.

Unlike an incandescent or a fluorescent, an E-Lamp has nothing to burn out. An electronic bulb doesn't suddenly go black, it just fades away. To put it simply, an E-Lamp is illuminated when radio waves excite a phosphor coating -- an efficient process that can save as much as 75% of lighting costs. Another potential saving: since it burns cooler than incandescents, the E-Lamp diminishes air-conditioning costs as well.

Ditto for bulb-changing labor. A significant share of the market will go toward replacing the "downlight" -- the hard-to-reach reflectorized bulb that shines (all too briefly) from within the ceiling fixtures of many offices. Even if an E-Lamp were left on all the time, an employee would have to change it just once every 2.25 years.

The bulb's nearest desktop competitor is the compact fluorescent, also a $15-or-so screw-based unit. But that bulb, spent after about 8,000 hours, can't hold a candle to the electronic bulb. Furthermore, the E-Lamp is smaller, fits into more existing fixtures, and isn't a shock hazard if it breaks. (Future versions of the E-Lamp will be dimmable, a boon for offices that want to lower lighting after hours.) And, despite the high frequencies generated within, the E-Lamp is said to disturb neither the stability of nearby VDTs nor the genes of nearby humans. -- Robert A. Mamis