Same as with the air conditioner, heating your house can take up a significant chunk of your energy bill.  It is not easy to estimate the energy use by your heater, it depends on the size of your house, how well the house is insulated, the temperature outside and the efficiency of the heating unit.  Following these guidelines will help reduce your energy use to heat your house:

• Set thermostat at the lowest possible temperature that meets your comfort level.  The smaller the temperature difference between the outside and the inside, the less energy it would take to heat up the inside.  For better efficiency, it is recommended to set your thermostat at 68F or lower.
• Lower thermostat’s temperature or turn off the heat if you’re leaving the house for over 4 hours.  If you have a set schedule every day, it might be good to invest in a programmable thermostat, so you don’t have to worry about remembering to reset the temperature every time you leave the house for extended period of time.
• Instead of using central heat, use space heaters, especially at night.  The investment will more than pay for itself within the first month.  I personally prefer the oil circulating heaters, versus the ones that have open prongs.
• The heat-generating appliances like the clothes dryer, oven, kitchen stove, dishwasher can help warm up your house, so use them when you’re home.