On Sun, 27 Jan 2013 08:37:25 -0800 (PST), Robert
wrote:

On Jan 27, 9:24 am, bud-- wrote:
On 1/26/2013 5:25 PM, bud-- wrote:



The graph I have goes to 90% voltage. At that point the life is
increased 50% (and rising fast). The lumens are 70%. At half voltage the
lumens would be a rather low percentage (far lower than 60W equivalent).

I read the wrong scale. At 90% voltage the life is already 3.5 x

The rule of thumb I've always seen is that the filament life goes at
about the 12th power of the voltage, which agrees with your number (5%
almost doubles life).

One more factor.... efficiency...

The lighting goes down fast,... the heat output ("light" we can't see)
goes up fast ...

No, heat goes down, too, just not as fast as the light output.

Hint: Incandescents, at lower voltage are great in seasons where
we would like more heat that light..... In the summer... not so
much...