Ford 2015 Focus Owner's Manual page 121

Starting and Stopping the Engine
The heater uses 0.4 to 1.0 kilowatt-hours
of energy per hour of use. The system does
not have a thermostat. It achieves
maximum temperature after
approximately three hours of operation.
Using the heater longer than three hours
does not improve system performance and
unnecessarily uses electricity.
119
Focus (CEW) Vehicles Built From: 16-02-2015, CG3630en enGBR, Edition date: 01/2015, First Printing