Andrew Gabriel wrote:
In article ,
Ian Stirling writes:
Mark Wood wrote:
Probably a FAQ but here goes...

What is the relative HEAT output from one of these bulbs?
I'm presuming a '20W Energy use/100w Brightness' saver bulb puts out little
heat and is perfectly safe to use with a '60W Max' dangly paper lampshade.

But wanted to check... :+/

About 6-8W or so comes out of them as light, the remaining as heat.
Maybe half the heat comes from the ballast, and half from the tube.
The surface temperature of the tube is often around 100C.

Ballasts are quite efficient nowadays. Most heat comes from the tube,
where a number of laws of physics still contrive to severely limit the
efficiency.

I have had occasion yesterday to open one, and repair the ballast (the
light was intermittent, which seems to have been fixed with a resolder),
and I'd be surprised if the heat from the circuitry much exceeded 10%.