On Dec 11, 8:44*am, dpb wrote:
wrote:

...

less power (though less than expected using your calculations) will
make the bulb less efficient (lumens per watt), costing you money too.

...

There's the same fallacy assumption that Lew made as well -- _ONLY_ if
one is requiring the same or more lumens will there be a higher energy
cost to obtain them--as told Lew, for household lighting, a 100W bulb is
a 100W bulb and one gets the light one gets (at least that's what I do).
* It's good enough and bulbs last.

No a 100W bulb is *not* a 100W bulb. Look at the rated output of the
bulbs at the given voltage. You generally buy a light bulb for light
(lumens) not heat (watts). If you have excess light use a smaller
bulb.

Sure it's not much for an ordinary 100W bulb so the convenience of not
having to replace them is a factor but there's no economic penalty
associated w/ gaining that (again, assuming one doesn't go from 75W _to_
100W per bulb).

You assume that a 100W 130V bulb puts out *exactly* the light needed
and that no less will do. Bad assumption.