Well that really depends on the inside temp of the house and cage. If you have no AC and it is 85-90 degrees outside then your house is going to be hot as well on the inside and even more so. The OP needs to specify temps and circumstances and then we can give the correct advice. If the temps are in the 80's or 90's in the house you can always use one of the twisty looking bulbs(I forget what they call them) that do not give off much heat versus a regular housebulb just to light up the cage. the inside of my house is at a constant 74 degrees so I always have a basking light on in my indoor cages.