Last night it got down to about 60 in the bedroom, and with the 75W dimmed to about 80% it was right around 68 this morning, which was fine. I turned it up to 100% this morning and the house has been at about 65-66 degrees and the tank is still just 70 degrees. So I'm just guessing that even with the daylight CFLs on the bigger terrarium, I may need a more powerful IR bulb to keep it at the right temps. Of course I will monitor it closely.