When we had our first Mass Save home energy assessment a few years ago, we received free compact fluorescent light (CFL) bulbs to replace our incandescent bulbs. Immediately our electric use started dropping. The CFLs use only a quarter of the power to produce the same light (measured in lumens) as incandescent bulbs, and lighting accounts for 20% of an average household electric bill. Also immediately we noticed that the CFL does not produce the full amount of light instantly; it takes a few minutes to warm up during which time the light output is steadily increasing. Not everyone in our family had the patience for that warm-up period, so we ended up switching out some of the CFLs for the old bulbs to result in faster light with less energy-saving. The Mass Save assessor left us the old bulbs so we didn't have to buy anything, and today we continue to use a few of those old incandescents.
Light-emitting diode (LED) bulbs solve the slow-start issue of CFLs while reducing energy use even further. Unlike the CFLs, LEDs contain no mercury so bulb disposal doesn't require special handling. LEDs have been commercially available for a few years now and prices are still dropping, but a typical discount through Mass Save or at a mall kiosk is $5/bulb or less. At that price the bulb pays for itself in electricity saved in less than six months. Apart from saving you money, the energy saved from 1 bulb that's on about 4 hours per day equates to about 100 pounds per year of carbon dioxide emissions from power plants. Last year Chelmsford residents replaced about 5000 incandescent bulbs with free CFLs or LEDs that they received in Mass Save home energy audits, preventing about 250 tons of CO2 emissions. Can these energy-saving bulbs be a big part of the answer to global warming?