Andrew Gabriel wrote:
In article ,
Ian Stirling writes:
Peter wrote:
I am planning light fittings in my new house and trying to get to
grips with fluorescent lighting. I can visualise how much light a
standard incandescent lamp will give, but find it very hard to do with
fluorescent fittings, particularly the smaller tubes.

Is there a good rule of thumb for comparing the output?

lumens are the measure of total light output.
Typical incandescant bulbs will produce from about 10-15lm/W.
Typical CF tubes a little under 100lm/W.
Larger linear fluorescents from 100-110lm/W.

These are ignoring control gear and other losses.

Modern control gear is usually over 90% efficiant, apart from
the low end CF tubes.

You need to halve them in practice (unless you hang a
bare fluorescent 12" below the ceiling with no fitting;-).

Why should this be so, when it's not true with conventional lights
(if done as a direct replacement)?


So, as a ballpark, around an eighth of the power is needed for
a fluorescent to be as bright as a conventional light.

4:1 is the normal figure used for compact fluorescent retrofits.