Depends on the temperature it produces at the distance (ground level) where the geckos are. If you're using it on the hot side, it should be between 86 and 90 degrees. Also be careful of the temperature if the gecks can climb up close to the bulb. I tried a 75 watt in my enclosure and the temp got to 100 degrees+ on top of the hot hide! Backed it down to a 50. Bob