Bearded dragon basking all day, or avoiding the lamp entirely
Too little or too much infrared
Is this urgent?
Not by itself. Basking all day, or avoiding the lamp entirely usually has an ordinary explanation, and the section below covers what to check. It becomes urgent when it arrives alongside one of the 5 same-day signs, or when it does not resolve once the cause is fixed.
From the guide · Lighting and heat · §3.4
Heat: power density, not surface temperature
This is the biggest shift in modern bearded dragon husbandry and it contradicts advice that’s still everywhere.
Basking bulbs (heat lamps, incandescent lamps, halogens) produce mostly IR-A, the wavelength that penetrates deepest, drives core body temperature, aids digestion and contributes to D3 synthesis.
IR-A comes from a hot filament. Incandescent and halogen lamps produce it because something inside them is glowing at a few thousand degrees. LEDs don’t; they are efficient precisely because they don’t waste energy as heat, which makes them useless as a basking source however bright they are.
Beam shape matters too. A flood spreads warmth across the whole animal; a narrow spot heats a patch of its back while the rest of it stays cold.
Wattage is not a specification you can look up. The same lamp at two different distances delivers completely different irradiance, so what works depends on your enclosure height and where the fixture sits. This is why the target below is stated in W/m² at the animal’s back rather than in watts at the bulb.
One bulb or two
A single basking bulb works, but in a 4-ft enclosure it tends to heat a bearded dragon unevenly, warm over the shoulders, cooler at the hips and tail. Two bulbs set side by side, a hand’s width or so apart, give a broader, more even basking zone from nose to tail. Where their beams overlap the infrared adds together, so two lower-wattage bulbs can reach the same power density as one hot one while covering more of the animal. If you go this route, measure the overlap zone; that’s where the dragon will sit, and where the combined figure has to land in range.
One more bit of geometry: a basking bulb almost never sits flush on the screen. How far the dome’s face floats above the mesh, the dome offset, changes the irradiance reaching the animal. A couple of centimeters is normal and fine; just remember it’s part of the distance, and re-measure if you move the fixture.
Why the temperature gun lies
Every material heats differently under identical infrared. Two spots receiving the same IR-A, verified with a power density meter, read completely differently on a gun.
| Surface | Gun reading | Infrared received |
|---|---|---|
| White half of test disc | 90.8°F | identical |
| Black half of same disc | 107.0°F | identical |
| Cork bark, correct infrared | 120–140°F | feels cool to touch |
| Light pavers, correct infrared | 90–100°F | suitable |
A test disc, half pale and half black, under one lamp. A temperature gun reads 90.8 Fahrenheit on the pale half and 107 on the black half, although a power meter confirms both halves receive the same infrared.
The basking surface temperature tells us practically nothing useful about the quality of the basking area. Every material heats differently whereas the dragon will receive the same infrared radiation hitting their back. Disregard anyone telling you that your basking surface needs to be a specific temperature; this has since become an outdated method that is ineffective. What matters is the wavelength and power density reaching your dragon’s body while basking.
Aaron Carter · Admin team, Reptile Lighting
Surface temperature and power density are not the same. One does not replace the other. They live on the same street, but not in the same house.
Thomas Griffiths · Admin, Reptile Lighting
There is a way to make the gun useful. Leave a digital thermometer face up on the basking spot for an hour, then compare its settled reading to the gun. In the test above, a gun reading of 90°F on the pale surface corresponded to roughly 108°F of delivered heat. Once you know your own offset the gun becomes a decent relative check.
The number that matters
Measured at the level of the dragon’s back. Power density doesn’t correlate with surface temperature or ambient temperature. It’s governed by distance from the lamp.
If you don’t own a power meter
Dr. Frances Baines of Reptile Lighting gives a hand test that works surprisingly well.
- 1.Hold your hand over the basking platform at the height of your dragon’s back and feel the warmth on the back of your hand, from above. It should be a gentle, evenly spread warmth you could sit under for several minutes without discomfort.
- 2.Then rest the back of your hand directly on the platform. It should be comfortable to hold there for a full minute.
If the lamp passes both, irradiance is very likely in the 250–350 W/m² IR-A range, because that’s what sunlight feels like on human skin.
There’s a slower backstop worth running once, when you first set up or change a lamp: leave everything on at full power for 3 hours, then read the basking surface with a temperature gun. This isn’t the primary measurement (surface temperature still isn’t what you’re tuning for) but it catches a spot that heats up dangerously over time, which a thirty-second hand test can miss.
Reading the dragon
Bearded dragons are biphasic baskers. They bask a few hours a day in two main phases, first thing when the lights come on, then again after eating, sometimes once more before lights out. The rest of the day is for exploring, digging and hunting.
| What you see | What it means |
|---|---|
| Basking all day | Not enough infrared. Or the enclosure is too small and there’s nothing else to do. |
| Avoiding the basking area | Too much infrared. |
| Two or three sessions, exploring between | Correct. |
Mounting over mesh
Mesh blocks infrared as well as UV, so a bulb chosen for an open enclosure will under-deliver through a screen. Correct for it like this.
- 1.Measure from the mesh to the animal’s back when basking. With a deep dome, measure from the bulb itself. Say 12 inches.
- 2.Find your mesh blockage, a standard screen is about 35%, so 0.65 passes through.
- 3.Divide the target range by what passes through: 300 ÷ 0.65 = 462 and 350 ÷ 0.65 = 538.
- 4.Find a bulb on an irradiance chart delivering 460–540 W/m² at 12 inches.
These are estimates and you may still need to adjust distance or wattage, but they get you close. If you have no UV index meter, set your basking distance from the UVB requirement first, then solve for the heat lamp.
Not sure this matches what you’re seeing? Ask Lizzy and describe it in your own words, or scan all 22 signs. A weight trend is the earliest warning for most of these, the free tracker keeps it.
Related signs
A community guide with general suggestions, not veterinary advice. If your dragon is unwell, please seek a proper diagnosis from an exotic vet. Guide last updated 27 August 2026.