In article ,
"Dave Plowman (News)" writes:
Even when fully warmed up their output just isn't the equivalent as
stated. I replaced a 100 watt large globe bulb with one claimed to be 100w
and it wasn't. And I doubt the globe one was the most efficient type of
incandescent bulb either. They probably use the same criterion as boiler
makers do for efficiency. ;-)

I've said this several times before, but the reason for this is
they are compared with softone filament lamps, which are painted
and lower efficiency, and are not what most people use.
Ignore the quoted equivalent on the box, and just assume a 4:1
ratio. For any kind of integral reflector bulb, it's probably
worse, i.e. somewhere nearer 3:1.

Also, you may want to replace old ones before they completely die.
I have a number which still work at 5 years old, but the phosphor
is noticably wearing out making them dimmer than new ones.

--
Andrew Gabriel