Lighting help-Powersun and Basking temp difference
 

I’m setting up a 36x18x12 enclosure for a baby Morrocan Uromastyx. I have three light sources-one 75w repti basking light and a 100W power sun as well as another uvb only bulb for the cool side. I check temps on the powersun and basking light and that 75w is reading 115 f and the 100W powersun is only at 107f. To me this isn’t making sense, having the powersun at a lower temp and a higher watt bulb. The measurements are taken from direct placement on the screen to 1/4 inch off the floor, approximately 12” span. I plan on keeping the warm side at 122-125 and the cool at 85-90, but am baffled at this, as I was told the powersun at 100W would be enough by itself and it’s providing less heat than the 75w basking bulb. Any thoughts or recommendations?

My only thought was the Powersun bulb could be a dud or someone returned a used bulb.

I could be wrong, the bulbs wattages are not the only thing that affect the concentration of heat. To me, a basking bulb is more focused to a specific area like a spot light and the power sun is more of a cover a larger area type bulb. This is the reason for different temps, the bulbs are designed for different applications.

I agree with Jason.

Even among incandescent basking lamps (such as the 75w you are currently running), there is a big difference between different brands in terms of heat spread and high temps at a given distance. I have a favorite brand that is based almost entirely on the focus of the lamp; when I try to switch brands I can't get the heat level/spread correct even with a dimmer.

I have experience with only a couple self-ballasted MV lamps (and this was so far in the past I don't recall the details), but you would likely find similar differences between brands of MV lamps as well. So trying a different brand of MV might give the temps you're looking for, or you might simply try the 160w -- depends if your application needs more overall heat or simply a better focus of the amount of heat a 100w MV provides.

Edit to add: AFAIK, as MV lamps age or fail, they don't get cooler (though the spectrum changes and they emit less UV). I doubt your issue is a bad/old lamp.