I wrote something up for you to show you how much goes into your care decisions. I hope it makes sense 
You can apply this same idea to get your optimal individual answer to all your monitor questions, like food, enclosure design, humidity levels, exercise, soil choices, etc..
Basking spot formula
FIRST decide what your desired ranges of temperatures are! There’s you’re goal.
If the basking spot is your only source of heat, it will also need to keep the rest of the enclosure at the proper low and midrange temps.
What you need
Temp gun - proexotics sells a inexpensive one, can be shipped to your door!
Heat retaining surface - darker colors hold heat better
Light fixtures - and a safe way to mount them to your enclosure
Bulbs that put out heat – NO clear centers!
Like all animals, some are prone to getting into trouble, some aren’t very bright. Some monitors will leave the light fixtures alone, some won’t. If you are going for a nice toasty basking spot, chances are it is close enough for the lizard to leap on and accidentally burn itself. You may have to create a light box of some sort. I made one out of hardware cloth. It served its purpose, but it was hard to use. Needed a better design.
Variables inside the enclosure
Where to mount your light(s) within the enclosure
Size of the enclosure
Size of the basking spot
Wattage of bulbs
Bulb intensity over time – some bulbs cool off long before they burn out!
Height of the bulbs from the basking surface
Color of the basking spot
Ventilation, airflow inside your enclosure
Size of the monitor
In my opinion, the basking spot should be large enough to heat the entire body. One bulb for a large lizard can lead to burns if it has to bask forever to warm its entire body. The larger the enclosure, the more heat you will need to provide for the proper range of temps. Depending on the size and shape of your enclosure, you will have to decide where to place your basking spot in order to get the full range of temps. Don’t forget to factor the size of your monitor, as it grows it will get closer to the lights while basking thus changing the amount of heat it receives. Airflow should be very minimal so you don’t let the important heat AND humidity inside escape. Do yourself a huge favor and stay away from screen enclosures or tops! Bulbs, especially ones that remain on 24/7 can loose their heat intensity over time. No special bulbs required, however, make sure they are NOT spotlights! Once you have discovered your formula and the temps are established, test the spot every few days (forever) to insure it is functioning properly.
Variables outside the enclosure
Weather in your area
Enclosure placement in relation to sun
Enclosure placement in the home
Use of air-conditioning/heaters
The above things can change the temperature inside your enclosure to uncomfortable levels, ESPECIALLY if the variables inside your enclosure are having problems. Enclosures near windows or walls that get hot during the day are prone to more radical temp changes. Sun exposure at different times of the year can affect enclosure temperature, as well as cold windy weather. Cold can be tolerated for short periods of time, provided your lizard is healthy. The cool spots in the enclosure are as important as the hot spots. It is important to track those as well. Test some regular spots with your temp gun every day/few days to check your status. If the temps are not where you have decided they should be, choose what you consider would be the most helpful variable and change it. Then test again for some hours or even days. Repeat as needed. As often as needed.
Additional choices for heat
Plug in hot rocks - cut the cord off! Causes burns
Human heating pads – excellent choice for heated hides
Ceramic heater – not recommended (by me anyway)
Pig blanket for large monitors – interesting, I would like to try it, but have no need atm
And more I can’t think of right now
Whew, enough babble,
-H-
