Bearded dragons don’t have a single “correct wattage” of UVB because the right output depends on the type of bulb (T5 HO vs. T8), the fixture and reflector, the distance to the basking spot, and whether the UVB shines through mesh. As a practical rule, most adult bearded dragon setups use a high-output T5 UVB linear tube in the 22–24 inch range, commonly rated around 24W to 39W depending on length and brand. Smaller enclosures often use shorter tubes (and lower wattage), while 4x2x2 foot habitats typically benefit from a longer, higher-watt tube to create a wide, usable UVB zone.
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For many common terrariums, a T5 HO UVB tube is the go-to choice. A 24W T5 HO tube is often suitable for mid-sized setups when mounted at an appropriate distance, while 34W–39W tubes are frequently used in larger enclosures to provide consistent coverage. T8 tubes tend to be lower output and may need to be placed closer to the basking area to be effective, which can be harder to do safely and reliably.
UVB intensity drops quickly with distance. A higher-watt, high-output tube can provide usable UVB at a safer, more flexible mounting distance, especially when paired with a quality reflector. Also, bearded dragons do best when the UVB spans a large portion of the enclosure (often about half to two-thirds of the tank length), so they can self-regulate by moving in and out of stronger light.
Position the UVB so it overlaps the basking zone, and verify the manufacturer’s recommended mounting distance—mesh tops can reduce UVB output. Replace bulbs on schedule (often around 6–12 months depending on bulb type and brand) since UVB output declines over time even if the lamp still looks bright. For a detailed, scenario-based breakdown, visit https://guilleni.com/how-many-watts-of-uvb-do-bearded-dragons-need/.
Most UVB bulbs need replacement every 6–12 months because UVB output weakens over time. Check the bulb’s packaging guidance and replace sooner if your dragon shows signs of reduced activity or poor basking response.
