In article ,
Huge writes:
On 2009-08-30, bof wrote:

Looks like CFLs are now officially dimmer that they claim to be:

http://www.telegraph.co.uk/news/worl...7/Energy-savin
g-light-bulbs-offer-dim-future.html

What a surprise. Not.

The manufacturers are currently pushing the EU to allow them to
remove the power rating from CFL lamps, arguing that it's only
confusing consumers. Not as much as their incorrect claims of
filament lamp equivalency are.

As regulars on uk.d-i-y will know, I've been pointing out the
misleading claims of equivalency with filament lamp ratings for
many years. My recommendation is to ignore the equivalency given
on the packaging (which is usually 5 or more times the CFL rating).
Feit (sold by Costco) is the only make I've seen in the UK with
realistic filament equivalancy ratings on the packet.

The most efficient CFLs are those with exposed tubes, and amongst those,
it's the ones with the tubes separated as much as possible -- well
spaced out. For these, use a general rule of a 4:1 ratio for filament
lamp to CFL equivalency. So to replace a 100W filament lamp, you'll
be looking for a 23-25W CFL. (18W is the highest stocked by most
supermarkets, which is why you may be struggling to find something to
replace a 100W filament lamp.)

As the lamp is made more compact (tubes squashed closer together)
which is required to fit in some light fittings, the folded tube
limbs start significantly shadowing each other and efficiency falls.
For the most compact ones, you're probably looking at a 3:1 ratio.

CFLs which have an outer bulb covering the tubes will lose effiency
in this outer bulb, and they usually have a more compact folded
tube arrangement in order to fit into the outer bulb. (The one
place where they can win is when used outdoors in an exposed windy
location, where the outer bulb will help the tube to warm up to
the correct temperature without suffering from wind-chill.)

CFLs with integral reflectors have the lowest efficiency of all,
because the large light source inherent with a CFL is really bad
for designing efficient reflector lamps. The smaller the reflector
with respect to the tube physical size, the worse the efficiency.
The really small ones have a ratio sometimes worse than 2:1, so a
7W reflector CFL is equivalent to approx 14W filament lamp, although
it will probably claim to be equivalent to a 30W lamp on the package.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]