My bet is the heating wires under the driveway failed and the previous owner (or the one before that) decided it wasn't worth fixing and reallocated the breakers. There may not even be any visible controls, the whole thing may be buried. But you'd expect there'd be a "loose" wire inside or outside the panel that goes out.

You may be able to do a continuity test to see if the loop isn't just broken, but I'm not sure what you'd be looking for. I'd try to establish that it's even remotely possible to get working before starting to look at panel upgrades. It may be a lost cause.

Thanks! I was wondering the same thing (about a past failure). A panel upgrade is necessary as we will need more room anyway for other projects. I'll try the continuity test as you say...if I can find the wires.

Be grateful that it doesn't work. If you are in a climate that gets lots of snow and ice, the amount of money and energy that would be used -- and wasted -- heating up the driveway (and the infinite heat sink that is the outdoors) would be huge. I grew up in Minnesota...trust me on this. You can hire someone on permanent retainer to clear off everything for you every time the driveway needs it and still be money ahead.

I'd guess they used it once or maybe even a season and after seeing the cost swore never again.

If the heating elements were the newer solid-state variety that are self-regulating (as in the solid state pipe tape), the system could be self-regulating and turn itself on and off based on ambient temperature. But, as pointed out above, the electrical cost could be quite high to operate. I would opt for a snow blower.