true 1 hour in very cold temps does not do much,It all depends on your over night low(s) and where it is inside or not.This part of canada hovers around freezing and a cold snap pulls overnight temps down in to the teens,however Iam in a garage and when I park for the nite the engine retains temp for 4-5 hours(it weighs about 900#) so 1 hour is enough to make for easy starting,if I want a warm cab or during a cold snap 2-3 hours is good.These block heaters melt cheap extension cords and need a heavy duty timer.I like the stick on pan heater for the transmission but only for extreme climates(alaska,yukon).I also have my doubts on the longevtiy of the stick on units,but if you dont have a block heater from the factory they are a good compromise.