Forget the heated drieway idea. They are not worth the time effort or
expense.
I worked on a system in stalled in a sidewalk at a bank(electric) and I
worked at acolledge that also had a heated walk way.
You can sit here and cost average the the system to death and the one
thing that everyone forgets is that melting snow or ice turns into water
and water turns back into ice. Can you start to see the picture?
Snow or ice accumulates, system turns automaticly or manually , snow
and ice melt ,system turns off . walk or drive returns to freezing temp
and mlted snow or ice reforms into ice so the system turns back
on........... What usually happens is the stupid thing stays on longer
than it is off.
As far as the bank s system , I never went bac to that job. As far as
the colledge they just turned it off and went back to shovels and ice
melt.

Bill