Halogen basking bulb wattage for bearded dragons

Good move switching to halogen — incandescents are inefficient and the heat output drops unpredictably as they age, which makes it hard to dial in a stable basking spot. Halogens run hotter and more consistently for the same wattage, so the first thing to know is you'll likely need to go down in wattage compared to what you were using before. To get this right: what size is the enclosure, what wattage incandescent were you running, and how high above the basking surface is the bulb mounted?

Perfect setup to work with. At 30cm distance in a 4x2x2, a 100w incandescent was likely just about hitting the mark — but halogens punch harder, so dropping straight to a 75w halogen flood is the right starting point for an adult dragon. You're aiming for a basking surface temperature of 40–42°C for an adult, so grab a temp gun or digital probe and measure the actual surface, not the air. Don't rely on feel or an ambient thermometer. What bulb were you looking at — do you have a brand in mind already?

The Arcadia Halogen Heat Lamp in 75w is the one I'd go with for your exact setup. It's a par38 flood format which gives a wide, even basking zone rather than a tight hotspot — that matters because bearded dragons need to fully thermoregulate across their body, not just warm one side. At 30cm mounting height, 75w in a 4x2x2 should land you right in that 40–42°C surface range. The 100w version risks overshooting and you'd end up raising the mount height anyway, which can create an uneven gradient. Start with the 75w, measure the surface temp on day one, and adjust mount height by a few centimetres if needed rather than swapping bulbs.

No — the halogen swap is purely for the basking heat source and doesn't affect your UVB at all. Those are separate jobs done by separate bulbs. Your UVB setup stays exactly as it is. The one thing worth checking while you're in there: make sure your UVB tube is still within its replacement window. If it's a T5 HO tube like an Arcadia Dragon 12%, those need replacing every 12 months even if they're still emitting visible light — the UV output degrades well before the bulb visibly dims. How old is your current UVB tube?

8 months is fine — mark the date on the fixture so you remember to swap it around the 12-month mark. The Arcadia 75w halogen is a solid choice and you'll notice the basking spot stabilises much more consistently than the incandescent. Measure surface temp the first day it's running and you should be good to go.