Chameleons like daylight heating. The basking spot should be in the high 80s during the day with an environment to be around 75F.  The 50W or 75W basking bulb is recommended for enclosure size 18 and Size 24 for summer with room temp not above 80F. 50W heating bulb is also available for size 16 and smaller enclosure. Please make sure your basking spot or branch is about 3-5inches away from the heat bulb. 100W bulbs can be used in a houshold during winter when the heater is not on(room temp around 60s).

Note: The 100W Basking bulbs are rated for 2000hours usage. For 12 hours a day on time, this means 167 days or around 5 months. However, oil from finger or water splash to the bulb will shorten the lifespan of the bulb, so please avoid touching the bulb with your finger and use a tissue or napkin to screw on bulb.