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My lamp says "Max 40W or Energy Saving 8W".

I have a halogen bulb which says "28W = 36W".

Is it safe to use with the lamp? Why / why not?

(Sorry if the answer is easily available on the web - I did search before posting here!)

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Why would a light fixture allow a 40W incandescent, but only an 8W "Energy Saving" lamp? A 40W incandescent is going to dissipate almost exactly 40W of heat (around 39W at 2% efficiency) while a 20W CFL is going to dissipate no more than 20W of heat (around 18W at 10% efficiency) –  Johnny Dec 4 '13 at 23:35
If the lamp has a dimmer, things may get muddier - I have wall-type LED capable dimmers that will happily do 600W incandescent (or 1000, I don't recall, since it doesn't apply) that will only permit 150W of LED (and either the same or some other number well below the incandescent rating for CFL - again, does not apply since I'm using them for dimmable LEDs, so those are the numbers I remember.) However, if that's the case, Halogen is incandescent, so no problem for the actual question. –  Ecnerwal Dec 5 '13 at 3:26

3 Answers 3

The safety concern is about heat, not light. For the safety label concern, you can put 40 actual watts of whatever you want in there.

But the real world is a bit more complex. Incandescent and halogen will run hot with little fuss. CFL's and even more so LED's have electronics that degrade under heat, and LEDs loose efficiency with heat. This is why both perform quite poorly in can lights and enclosed fixtures.

All that said your 28W halogen in a 40W fixture is just fine. I'd stick to a 18W or less CFL or LED for operation heat (not safety heat) reasons.

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this is a thoughtful (and entirely plausible) answer. In this case, the 40W limit is the maximum heat that the fixture can safely take, while the 8W limit would be the fixture manufacturer's estimate of how much heat would be too much for an energy saving bulb's electronics to sustain. I buy it. –  mac Dec 5 '13 at 14:46

I would think that you should be OK. You're using a 28W appliance in a 40W fitting, which is within recommended specifications.

As far as I understand, energy-saving bulbs are either CFLs (compact fluorescent lamps) or LEDs (light-emitting diodes). A halogen bulb is still an incandescent bulb, but the materials it is built with are different.

Your halogen bulb's label indicates that it consumes 28W to produce the light output of an average incandescent bulb that consumes 36W, hence saves power. But it isn't an energy-efficient bulb when compared with other available types, such as CFLs or LEDs.

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Yes. Because the 28w it will use is below the 40w rating for the lamp.

Johnny: I think the light manufacturer is saying: You can use a 40w incandescent or an 8w CFL since both give the same lumens of light. I think it is unintentionally confusing though because one may think that the maximum CFL wattage allowed is 8w, when any CFL up to 40w would be okay.

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Having read Bryce's comment above, I want to retract all of the above comment starting with "Johnny". I didn't consider the effect of heat on an enclosed CFL. –  getterdun Dec 7 '13 at 1:11

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