Well, the age/size of the chameleon matters as well, and so does the sex. Little ones shouldn't get as hot as adults. Females should be kept a few degrees cooler than males and fed a less to keep her from cycling big clutches. The wattage depends on your household ambient tempuratures. Assuming it's a male adult veiled it seems most here keep them between 90-95. A more specific tempurature suggestion could be given if we know the age and sex. Using a digital thermometer or a tempurature gun you'll have to experiment with the wattage to get the right tempurature.