There's really no average gas heating bill because the cost to heat your home with natural gas will depend on how much your natural gas rates are and how big of a house you're heating.
Although for some people with a 1,000 square foot house the natural gas heating bills come to around $190.00 to $200.00 per month.
Other things that will factor into how much your natural gas bill for heating will be how cold it gets in your area and how well insulated your house is as well as how high you keep the temperature on your thermostat.
You can expect at least $190.00 per month on the low side for a natural gas heating bill and on the high side $200.00 for 1,000 square foot house.