As of March 2015, heating with propane is more expensive than heating with natural gas but less expensive than heating with heating oil. It is more economical than electrical heating in most areas.
Propane prices typically vary more than natural gas prices, and the stability of the natural gas supply in the United States makes natural gas the top choice for powering boilers and furnaces. Fortunately, most propane and natural gas heating units can be converted to use either fuel, so those who invest in propane heating appliances can switch to natural gas if a gas line is offered in the future. Oil-fired units, on the other hand, are expensive to convert to another fuel type, if conversion is even possible.