Don, I'm trying to determine the difference in heat given off by a 100
watt BR-40 reflector flood, compared to a 100 watt BR-40 halogen
reflector flood. Typically these lamps are rated in voltage, wattage,
and lumens, but nothing tells me how much heat is given off.
Thanks for any help,
There is no differance in the heat given off by light bulbs for the same
wattage. All the power is converted to heat. What little power in the
actual light is converted to heat when it hits something in the room. Maybe
a few photons escape by the windows, but not enough to make it noticable.
If ballasts are used, their heat must also be factored in.
If I have two 75 watt, A19, 120 volt lamps, one is a standard lamp which
puts out 1190 lumens, and the other is a rough service which puts out
800 lumens, you're saying they both put out the same amount of heat?
If they both actually draw 75 watts from the power source, they will put out
the same amount of heat.
The amount of lumens tell how efficient they are at converting electrical
imagery to light.
If you put them both in the same room, the one with the most lumens will be
brighter. Put them both in the same size box, and the two boxes will heat
up the same.
If the question is how much heat is added to a room that is the right
answer. It is what air conditioning guys might want to know.
If the question is how much heat is created at the bulb (at the fixture)
the 800 L rough service bulb gives you more. A complicating factor is
whether the heat from the 2 bulbs is as likely to radiate from the
fixture. Don has often said CFLs create heat that is not as radiant.
A question not asked (but probably obvious) is if you can use a smaller
wattage halogen lamp that has the same useful lumens out of the fixture,
the heat that is added to the room is smaller because the wattage is
Another way of looking at it is: If you have 75 watts of power
into the room, and nothing going out, the room will heat up. It
matter whether it is a toaster, a light bulb, a space heater, a TV
or an electric toothbrush. What matters is the amount of power going
into a sealed room..... It ALL turns into temp rise unless there is a
some part of it to radiate out.......
Andy in Eureka, Texas
PS I do not endorse using a 75 watt toothbrush as a
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