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

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.

The wattage equivalent on a lot of CF tubes is somewhat debatable.

The catch is they are compared with light output from 'soft'
coloured filament lamps, not what you normally use (and CF
retrofits are nearly all 2700K to match regular filament lamp
colour anyway).

--
Andrew Gabriel