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.

Of course, switching to natural gas or propane requires a new boiler or furnace. An efficient wall-mounted natural gas or propane boiler will cost about $10,000.

While switching to natural gas might pay off, remember that, like oil, natural gas is a limited resource, and when supply is tight, prices can spike.

Wood-Pellet Boiler

Wood-pellet boilers are a relatively new method of home heating. Wood pellets are made from whole round wood or wood-manufacturing byproducts, for instance sawdust. Heating a home that typically uses 1,000 gallons of oil would take approximately eight tons of pellets, costing a little more than $2,000.

The carbon footprint of a wood pellet boiler isn't yet known, but it is much lower than that of any fossil fuel-based system. Wood-pellet boilers are pricey, running about $14,500 for a full system. However, one dealer of wood-pellet boilers says the system will pay for itself in a little more than six years.

While wood is a renewable resource, it is not infinite. As a result, the price of wood pellets may vary with demand. There's one more catch: Wood-pellet boilers are growing in popularity, and many regions face shortages of both pellets and pellet boilers.

Electric Boiler

An electric boiler will cost about $2,000, plus installation expenses. Electric boilers have been around for a while. They're considered to be between 95% and 100% efficient, but because of the high price of electricity, they're not particularly popular. It would cost more than $7,000 to heat your home using an electric furnace or boiler (assuming a cost of $0.167/kwh). But here's the real kicker: Because most of the electricity in this country comes from coal, an electric system would spew more than 54,000 pounds of carbon dioxide into the atmosphere.

The environmental and financial impacts of an electric system may make it a definite no-go, but there are ways to make an electric heating system a little gentler on the environment and your wallet in the long run.

By installing solar panels, you can reduce the amount of electricity you get from coal. The amount of electricity generated by solar panels varies by region. In Maine, for example, you can expect to get 1,300 kwh/year from a single one-kilowatt panel. In southern California, you can expect to get 1,800 kwh/year per installed kilowatt. Solar technologies are changing, but one installed kilowatt will cost about $9,000.

Geothermal Heat Pump

Another way to make an electric system more environmentally and financially friendly is by adding a geothermal heat pump. A geothermal heat pump uses the stable temperature of the soil relative to the air to heat your home in the winter and cool it in the summer.

Installation is expensive -- it can run upward of $30,000 -- but the system pays for itself in energy savings in five to 10 years. After that, you only have to pay for the electricity to run the pump (estimated at about $1,000 a year). Of course, if you install solar panels to power the system, you could have free heating for life.

Determining which option is right for you depends in large part on your local choices. Is natural gas available in your area? Are wood pellets available? Likewise, consider the age of your oil furnace or boiler. If it's 20 or more years old, you may need to replace it soon anyway, and that could make this the perfect time to switch to another form of heat.
Kelsey Abbott is a freelance writer in Freeport, Maine, where she lives with her husband and their dog.