3l. CFL Analysis - Efficacy

Though CFLs may give a little more light (lumen) per watt than incandescent lamps - a normal quality-quantity trade-off - the "5 times more" is only a nominal value for some of the best, top brand, bare tube 'single-envelope' CFTs & CFLs:

a) in the beginning;
b) in optimal burning position, at optimal temperature & humidity, in optimal luminaire;
c) if they have a good power factor;
d) if the heat replacement effect is ignored;
f) if they last as long as promised (without losing too much output towards the end).

"During 2004, the Test Laboratory then a part of the Swedish Consumer Agency (now a part of Swedish Energy Agency) carried out its second ad hoc testing of 20 different CFLs from Osram, GE, Philips, IKEA and Sylvania. The testing authority concluded that there was no correlation between price and performance of the CFLs.

The information on packaging was often deficient in terms of light quantity. Many models had light output claims that could only be achieved at the optimum operating temperature and/or in some optimum burning position that achieved an optimum internal temperature.

"Many light output claims were outright exaggeration, often by about 15 percent and in a few extreme cases by 25 percent. Furthermore, it was common that the indicated life was inaccurate."[emphasis added] [1]

Other consumer tests have found the poorest performing bulbs in each test to give >15%, 19%, 22%, 33%, 34%, 65% less light than stated, while a few of the best gave slightly more (initially), and most somewhat under stated lumens. [2, 3, 4, 5, 6, 7]

Update 29 Aug: A new test by The Telegraph sample 11W CFLs to give only 58% of the light from the claimed equivalent 60W incandescent lamps. [8]

1. Swedish Energy Agency: Compact Fluorescents in Residential Lighting
2. Vielen Sparlampen geht das Licht zu früh aus
3. 14 Sparlampen im Test
4. Råd & Rön, 1/2008
5. Ica-Kuriren, 3/2008
6. Öko-Test Themen-Special: Energiesparlampe versus Glühbirne
7. Die Tester: Energiesparlampen
8. Energy saving light bulbs offer dim future