I have a friend with a driveway heater, she says it’s way too expensive to use to melt the snow. They shovel/plow/whatever the majority, and use the heater only for the last little bit.
You can also try one of these, hand-held, 100,000 BTU, 2000[sup]o[/sup]F, runs on standard propane. Good enough to clear off the walk, I’d guess. My dad has one, I don’t think he’s ever tried it on snow, hmm…
Why not just spray anti-freeze on it? The snow will melt, and the melted water will not freeze.
And it’s not harmful to the environment. It’s just coloured water, right? Right? 
[snappy little theme song]
“That name again, is Mr. Plow!”
[/snappy little theme song]
I konw you’re joking Spiff but please everyone, don’t spread anti-freeze around. It’s sweet tasting and poisonous, and can kill dogs and cats who drink it.
Let me guess…you’ve never had to fold laundry before, right?
Anthracite: No, I’m not mixing them, I’m saying they’re working in harmony. 
When I was a kid, shovelling the snow, I wondered why they couldn’t just lay pipes under the driveways & walkways, and pipe steam through them. When I was older, I found out that they do indeed do this in some places. One of those places is Moscow, where one poorly-maintained system ruptured a pipe & turned the earth beneath the street to really hot mud. The pavement collapsed, and some people fell through & were scalded to death. Just a little story to scare those do-it-yourselfers out there.
In all seriousness, there are a lot of chemicals one can use to melt snow or ice. Plain ordinary sodium chloride is the most commonly used, but you can also use, for instance, ammonium ureate, which has the advantage that it’ll also fertilize your lawn in the process.
Downtown Holland, Michigan has completely heated sidewalks and streets. There is a power plant ~3/4 of a mile from downtown, and the steam is routed through radiant pipes under all the streets to melt snow. It was a bitch it install, but works quite well. Obviously having a source of free steam helps!
Back in college, the dorms had steam heat, with pipes radiating out from a central steam plant to each building. In the winter it was obvious where those pipes were, because the ground was always dry above them when it was snowy, except for really heavy snowfalls.
Of course if you used it for your driveway, I imagine it’s a gradual short of thing to completely melt the snow away, but the good news is that you should have a minimal refreezing problem.
I still think my calcium carbide idea is pretty damned dramatic. The effect would be a big huge flaming snowbank. :eek: 
Same thing at my school. A huge (5 foots wide) path always appears right under the football field. I always thought that I should not pay the school rent, and just live in a tent year round above one of these spots.
I always prefered being in them, rather than on top of them. It’s a lot warmer and the temperature isn’t variable at all, and there are some lovely rooms and corridors that one could stay in for very long periods of time without attracting attention. I spent a couple hours in ours earlier this week.
Having used calcium carbide in caving, and made…ummm…items with it that make big booms (as experiments), I have to say that the idea of a huge, exploding, flaming snowbank sounds
COOL!
Una