Heat lamp substitute?

[J-Man]

I was wondering... is the use of a heat lamp solely for the heat? or also the lighting? Because I discovered today that a space heater might be a very good substitute for a heat lamp. I don't really know how to put it in words, but if you put it right by the cage you can literally move your hand from one side of the cage to the other and feel the difference. So they can still thermoregulate but there's no light... has anybody ever done this before? just a thought.