Regarding the parking lot power outlets for block heaters, the way most of these work is by a temp sensor at the main, which cycles the outlet on+off, at a frequency determined by outside temp. for example, if the outside temp is -15, they are on for 10 min, off for 10 min, if it is -20 they are on for 10, off for 5 and if below -25 on continuously. Otherwise, lots of power is wasted. With this cycling, some power is saved and people can come and go at different times. Any car, no matter the temp, needs the heater activated for a max of 4 hours before starting. Not only does the block heater aid starting, but its REAL benefit is that the heater starts pumping out warm air a lot sooner. For most of us, that is the real plus!