Ice resurfacing machines themselves are HEAVY, especially when filled with snow scrapings. Plus, they carry fuel and water tanks. If the rink does frequent ice cuts, there may not be enough time between cuts to charge an electric machine. Not to mention that the facility would be dependent on reliable workers to keep it charged between uses. (Uh, I forgot - no ice cut before freestyle, of course. It'll be ready to go by open hockey time, though. Snicker)
The machines don't "melt" the ice per se, the blade scrapes the ice surface, the shavings get dumped into a hopper by the auger, and the operator sprays heated water from a tank for the cloth at back of the machine to spread. The engine has to heat the water, power the hydraulic lifts as well as drive the heavy machinery around the rink. After the cut, the scraped snow is dumped into a pit or melt pile; the ice resurfacer doesn't really melt it, nature does. (That's why you always see snow piles behind ice rinks when it's cold out.) I don't think the machine heats the hopper - that would be a safety issue. Maybe there is some heating to keep the snow from getting frozen inside the hopper. Do you have a source for that function?
I don't think electric technology is at a point where they can produce a cost-effective ice resurfacer. Although, I'd love it if Santa brought me a Tessla...♥