Is 150 watt bulb too much for a bearded dragon?

When it comes to heating and lighting for bearded dragons, owners often wonder what wattage bulb is best. A common question is whether a 150 watt bulb is too much for a bearded dragon enclosure. The short answer is that it depends on the size of the enclosure and the ambient temperature of the room. Bearded dragons require adequate heat and UVB light to thrive, but too much heat can also cause problems.

Ideal temperatures for bearded dragons

Bearded dragons are ectothermic, meaning they rely on external heat sources to regulate their body temperature. Proper temperatures are critical for digestion, immune function, and activity levels. Here are the ideal temperature ranges:

  • Basking spot: 95-110°F
  • Cool end of tank: 80-85°F
  • Nighttime: 75-80°F

These temperatures should be measured with a reliable thermometer placed at the dragon’s basking spot and cool end. The basking area should be the warmest part of the tank directly under the heat and light source.

Factors that determine proper wattage

There are a few key factors to consider when choosing a wattage for your bearded dragon enclosure:

  • Tank size – Larger enclosures need higher wattage bulbs to heat up sufficiently. A 150 watt bulb may be too much for a small 20 gallon tank but not enough for a large 120+ gallon enclosure.
  • Ambient room temperature – If your house is kept very warm, a lower wattage may be adequate. Conversely, a colder home needs a higher wattage bulb.
  • Type of bulb – Some bulbs are designed to produce more concentrated heat than others. Mercury vapor bulbs run hotter than basic household incandescents.
  • Use of undertank heater – An undertank heater or ceramic heat emitter paired with a lower wattage basking bulb can help provide sufficient heat.

Is 150 watts too much?

Generally, a 150 watt bulb is only appropriate for very large enclosures of 120 gallons or more. The extra heat from a bulb this powerful can make it very difficult to establish a proper temperature gradient with a sufficiently cool end.

However, in some situations a 150 watt bulb may work:

  • Extremely large enclosures of 200+ gallons
  • Tanks kept in unusually cold rooms (under 70°F)
  • When used with a dimmer or thermostat to control output
  • If elevated very high above the tank to disperse heat

Otherwise, a 150 watt bulb carries risks of overheating smaller tanks. Temperatures exceeding 115°F can stress a bearded dragon and cause health issues over time. Burn injuries are also possible from surfaces that are too hot.

Recommended wattages by tank size

Here are some general wattage recommendations for various tank sizes:

Tank Size Wattage
20 gallon 50-75 watts
40 gallon 75-100 watts
60-75 gallon 100-125 watts
90-120 gallon 125-150 watts

These are general guidelines only and may vary based on room temps, bulb type, and other factors. Always check temperatures with a thermometer at the basking spot when adjusting wattages or bulb heights.

Signs of overheating

Look for these signs that your bearded dragon is too hot:

  • Gaping or holding mouth open
  • Panting
  • Pressing body against cool surfaces
  • Digging or scratching at tank walls
  • Darkening skin color
  • Lethargy
  • Loss of appetite

If you notice any of these behaviors, turn off the heat lamp and check temps. Your dragon may be overheated from a bulb that is too powerful.

Providing a heat gradient

In addition to a hot basking area, bearded dragons also need access to a cooler zone. This allows them to self-regulate their body temperature by moving between warmer and cooler areas as needed. Good temperature gradients are:

  • Basking area: 100-110°F
  • Middle of tank: 85-90°F
  • Cool end: 80-85°F

A 150 watt bulb makes it challenging to provide a broad gradient, especially in tanks under 120 gallons. The entire enclosure may become too uniformly hot. Adding a second lower wattage bulb over the cool end can help establish a better temperature range.

Using lower wattage bulbs

Lower wattage bulbs around 75-100 watts are usually preferable for smaller and medium sized bearded dragon enclosures. Benefits include:

  • Easier to create temperature gradient
  • Cool end stays under 85°F
  • Less risk of overheating and burns
  • Less electricity usage
  • Bulbs last longer

Pair a 75-100 watt basking bulb with an under tank heater or ceramic heat emitter to help provide sufficient heat. Some options include:

  • 50-75 watt basking bulb with undertank heater
  • 75-100 watt basking bulb with 25 watt ceramic heat emitter
  • 65 watt daylight blue bulb with an undertank heater

With lower wattage combo systems like these, temperatures can be more easily fine-tuned and controlled.

Using a dimmer or thermostat

For very large enclosures, a high wattage bulb like 150 watts may be needed to provide enough heat. But excess heat can be controlled with a dimmer switch or thermostat.

A dimmer allows manual control of light brightness and heat output. Reduce output if the enclosure gets too hot. A thermostat automatically regulates temperature by turning the bulb on and off as needed.

With either system, the full 150 watts are available to initially heat up the tank. But the output can be decreased to prevent overheating while still providing adequate basking temps.

Consider bulb type

The type of heat bulb also impacts heat output. Although wattage gives an estimate of power, some bulbs run hotter than others:

  • Mercury vapor bulbs – Produce intense, concentrated heat and should only be used with large tanks and in very cold environments.
  • Ceramic heat emitters – Emit mostly infrared heat but little visible light. Good for nighttime and 24/7 heating.
  • Colored/specialty incandescents – Red, blue, and purple bulbs produce less intense heat than standard white incandescents at the same wattage.

Compare different bulb types to find one with ideal heat output. Lower wattage mercury vapors and colored bulbs may work better than high wattage standard bulbs.

Elevate basking bulb

Greater distance between the bulb and basking spot decreases intensity. Elevate a high wattage bulb farther above the enclosure to provide adequate, but not excessive heat:

  • 150 watt bulb: Elevate 15-20 inches above basking area
  • 100 watt bulb: Elevate 10-12 inches above basking area
  • 75 watt bulb: Elevate 8-10 inches above basking area

Use bulb hangers or drill holes in the enclosure lid to securely elevate lights. Measure temps at the basking spot when adjusting height.

Monitor temperatures

Always check temperatures when making any lighting changes. Use a reliable digital thermometer with a probe at the basking spot and cool end. Adjust wattages, bulbs, dimmers, and heights gradually to achieve a temperature gradient within the ideal ranges for bearded dragons.


A 150 watt bulb is generally too powerful for the majority of bearded dragon enclosures under 120 gallons. Lower wattage incandescent, mercury vapor, or colored bulbs around 75-125 watts are usually more suitable.

Pair these with undertank heaters or ceramic emitters if additional heat is needed. Use a thermostat or dimmer to fine tune bulbs over 100 watts. Check temperatures frequently when adjusting lighting to ensure a proper heat gradient.

With the right wattage bulb, thermostat, and basking spot distance, you can provide safe, healthy temperatures for your bearded dragon.

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