Outdoor Waste Bins How Long Must A Block Heater On A Car Be Plugged In To Be Effective But Not To Waste Electricity?

How long must a block heater on a car be plugged in to be effective but not to waste electricity? - outdoor waste bins

I have a 2000 Ford Taurus with a factory-mounted heater. I live in Canada, eh? I use a timer to turn the block heater to save electricity. When I leave the house at 8 clock, which provide time for a change of heating to get the best results of heating without electricity by using the block heater, more than it needs to be done? Is it time depends on the temperature? Thanks, - Tom