Efficiency

Compare brands for price, lumens per watt (LPW) and hours of life. To calculate lumens per watt, divide the lumens by the watts. For instance, an 800-lumen 60-watt incandescent bulb would have a LPW of approximately 13 (800 divided by 60); an 800-lumen 15-watt CFL would have a LPW of about 53 (800 divided by 15). Remember, the higher the LPW, the greater the efficiency and the more light you receive for the energy used.

Color

In addition, compare CRI and Kelvin Temperature if displayed on the product package—CRI will be a 2-digit number and Kelvin will be a 4-digit number with K, for example, 3500K. For an idea of how a room will look in varying shades of white light (warm–yellow or cool–blue), see the ENERGY STAR® Choose a Light Guide at http://www.drmediaserver.com/CFLGuide/index.html.

Instructions for Appropriate Use

When you purchase a bulb, check its packaging for any restrictions on use. For example, some bulbs should not be used in enclosed fixtures and some may specify that the base be up or down. Many are for specific fixtures, such as recessed cans, dimmer switches or outdoor fixtures. Bulbs used incorrectly can cause fire and/or electric shock. This pertains to incandescent bulbs as well, such as using a 100-watt bulb in a fixture that calls for 40 watts.

Source: UF/IFAS Energy Efficient Homes: Fluorescent Lighting, Hyun-Jeong Lee, Kathleen C. Ruppert, and Wendell A. Porter, FCS3270, 2008

Additional Resources

UF IFAS Energy Efficient Homes: Fluorescent Lighting - http://edis.ifas.ufl.edu/FY1031  

Consortium for Energy Efficiency. (2007).  Residential lighting. Retrieved April, 18, 2008, from http://www.cee1.org/resrc/facts/rs-lt-fx.pdf  

ENERGY STAR®. (2008, April) Frequently asked questions: Information on compact fluorescent light bulbs (CFLs) and Mercury, April 2008. Retrieved May 5, 2008, from http://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact_Sheet_Mercury.pdf

ENERGY STAR®. (n.d.a). Compact fluorescent light bulbs. Retrieved April 16, 2008, from http://www.energystar.gov/index.cfm?c=cfls.pr_cfls