Snow melting can be accomplished with GHPs; but, there are serious cost impacts on the residential side.
Due to the nature of snow melting, a separate system must be installed to serve the load. This is due to its requirement for the circulation of an antifreeze fluid through the system, instead of the warm air supplied by water-to-air heat pumps. Beyond this, since the requirement for snow melting coincides with the need for space heating, additional ground loop must be installed to serve the snow melting system.
Although GHPs produce heat less expensively than most other systems, because of the substantial quantities of heat required by snow melting systems, the annual cost remains high. The high energy cost is a result of the way snow melt systems are operated. Most systems are allowed to "idle" at a low heat output during the winter season. This allows the paved surface to quickly come up to temperature when snow fall occurs. The energy consumed by this idling operation, because of the number of hours over an entire season, is substantial. Because of the thermal mass of the paved surface, simply turning the system on when snow fall occurs results in a long time lag (several hours to one day) between start up and snow melting. This results in incomplete snow removal and a "corduroy" effect on the surface.
The high energy cost is compounded by the need for high water temperatures to produce the necessary output required for adequate snow melting. These temperatures, in areas where heavy snow occurs, are far in excess of what would be produced by available unitary heat pump equipment.
The following evaluation of a snow melt system for a residence in Michigan points out some of the limitations.
"In your area, a snow melting system would be designed for an output of about 165 Btu/hr per square foot, under melting conditions. For a 12 ft wide 100 ft long driveway, this would amount to 198,000 Btu/hr or the equivalent of about a 20-ton heat pump. This is about six times the size heat pump required for the average house.
For snow melting conditions below 30°F and wind speeds above 5 mph, required water temperatures in the snow melt loop are in excess of 130°F. This is higher than the average heat pump can produce.
Because the snow melting system requires the circulation of hot water, a water-to-water heat pump is required. Most homes with a geothermal heat pump use a water-to-air heat pump.
Snow melting requires a substantial amount of energy on an annual basis. In your area, a residential system would consume about 133,000 Btu/yr per square foot of driveway. Supplying this from a geothermal heat pump, at a COP of 3.5, would require an electrical input of 11 kWh/sq ft of driveway. For a driveway of 1200 sq ft (100 ft x 12 ft), this would be about 13,200 kWh/yr or $924 per year at $0.07/kWh."
Snow melting has been successfully incorporated into some commercial GHP systems serving gas stations/convenience store operations. The advantage here is that the store contains a great deal of refrigeration equipment which continually produces waste heat used for the snow melting system.
The moral of the story is that snow melting can be done with GHPs if money is no object. For most folks though, it's much more economical to hire the neighborhood kid to shovel the driveway.