Not much. Switching to an HID headlight and LED bulbs everywhere else gains about 30 watts on the 2001 and up, the earlier models already have a low wattage headlight, so switching everything else to LEDs will gain about 10 watts. 10 watts is enough to alternate grip and toe warmers on low, and everything else is a matter of proper wicking, insulation, and wind proofing layers. I've done extended rides in the 20s, commuted 15 miles in the teens, and ridden 5 miles across town for coffee at -11 just alternating toe and grip warmers on low, with polypropylene wicking, polypropylene fleece pants and shirt, mesh gear, a rain suit, and insulated boots and gloves. Also, Hippo hands and a good full face helmet with the vents taped shut. I would not go far dependent on electric heat because of the possibility of catastrophic consequences if a system failed.