In order to save on the electric bill, I keep the temp on 65 degrees F. Though the cats can easily survive that (considering they have been going outside when it was 30 degrees), they really don't like it.
I have a little electric space heater near my computer for my feet (bad circulation due to diabetes means my feet freeze even with socks on). I swear the cats know the sound of the fan on this little heater.
Yesterday I was sitting at the computer and my feet got cold. So I turned the space heater on. The picture below was taken two or three minutes later--and neither of these cats were anywhere to be found before the heater was on... 
Orange and Squeak soaking up the heat
