When I was retired & wife was still working I put a small electric heater in her car directed toward wind shield. It would melt the ice off the wind shield ETC . It would be toasty warm inside. Had a extension cord ran from patio to drive way. Would plug heater in to cord at night . When i got up I would plug extension cord in on patio. If you do this be sure extension cord is heavy enough to carry load. Wife really liked hopping into warm car.