In article ,
David Hearn writes:
We have a 300W halogen up-lighter with built in dimmer. It also has a
50W bendy spotlight with dimmer.

I'm aware that 300W is a lot of electricity, and in fact, it's too
bright when on full - we tend to have it on 50% or less.

My parents have a 500W one. They often run it in the evenings with
a light output equivalent to about a 40W bulb. I stuck a true power
meter on it, and at this level it was consuming 300W.

Does dimming a light reduce the electricity usage? Part of me says yes,
but another part of me is less sure.

Yes, but not by much in comparison to drop in light output.

I'm thinking of looking for a 150W lamp to go in there which would be
more reasonable - especially if dimming has little effect on electricity
consumption.

I think 200W is the smallest you can get that type of bulb,
but that rating isn't common and you might have to search.
The 100W and 150W ones are shorter.

--
Andrew Gabriel