A 5W heat pad will be apple for a young hatchling / juvenile beardie for several months.
ie
http://www.reptiledirect.com.au/p/85/GC ... at-5W.html , I connected mine to a thermostat to make sure they never got warmer than my desired temperature (36oC for beardies) , and sandwiched them between old ceramic tiles
A few tips in using these items:
1. These items are not waterproof so should never be emersed in water.
2. It is often best to place the heat mat outside of the enclosure to prevent overheating, and to protect the heat mat from getting wet or dirty. The heat mat can be placed under your enclosure or even attached to the wall of the enclosure depending upon your needs.
3. Ceramic tiles are good conductors of heat and can be used as a buffer in situations where less intense heat is required. Just place a ceramic tile on the heat mat such that the ceramic tile can give off the heat that your pets require. It is also a good idea to place a heat resistant barrier ( such as a piece of glass or tile) under the heat mat to seperate the heat mat from combustible materials and protect any furniture that the heat mat and enclosure may be sitting on.
4. Ensure adequate ventilation around the heat mat.
5. Set your enclosure up completely BEFORE you put any animals into it so that you can test and ensure that the heat mat is achieving desired temperatures. A good thermometer and/or thermostat can help with maintaining correct temps and these items are available seperately in ebay stores.
6. Put the heat mat toward one end of the enclosure as you should have a heat gradient which results in a warmer end of the enclosure and a cooler end of the enclosure.
7. As a rough guide a heat mat that is about a third of the floor size of your enclosure will provide appropriate heat for that enclosure. This is not a rule of course but a good rough guide.