If car is frozen how long will it take for the block heater to warm it up?

The time it takes for a block heater to warm up a frozen car engine can vary based on the outside temperature and the specific heater used. Typically, it may take anywhere from 1 to 4 hours for the block heater to sufficiently warm the engine to facilitate easier starting. However, in extremely cold conditions, it may take longer. It's generally advisable to plug in the block heater several hours before you plan to start the vehicle.