Just because summer isn't over, it's not too early to start thinking about how you're going to stay warm this winter. For those of you heating your homes with oil, it might be time to take a look at alternative heating methods. Is it time to switch to another fossil fuel, such as natural gas or propane? Will a wood-pellet furnace give your wallet (and the planet) a break? Or is geothermal the way to go? To figure that out, take a look at what a winter with heating oil would look like. Say you use 1,000 gallons of oil to heat your home. Given the current price above $4 a gallon for No. 2 oil, this year's bill would be more than $5,000. What's more, heating your home will send more than 28,000 pounds of carbon dioxide into the atmosphere. You could huddle by a wood stove all winter, but there are other ways to heat an entire house that are cheaper and less carbon-heavy. Natural Gas and Propane Natural gas burns more cleanly than oil, releasing just over 19,000 pounds of carbon dioxide to produce the same amount of heat as 1,000 gallons of oil. And natural gas is currently cheaper than oil, costing about $2,600 to heat a home at today's rates. Propane is a byproduct of petroleum refining and natural gas processing. Heating with it would cost about the same as heating with oil. Per gallon, propane is cheaper ($3 a gallon), but it is less efficient than natural gas or oil. To heat that same house with propane would cost more than $5,300, and it would release about 22,000 pounds of carbon dioxide to the atmosphere.