Formats

• LPG is used in furnaces and also in efficient catalytic heaters that burns the liquid petroleum at a lower temperature. Electricity is also used in furnaces, along with radiators and space heaters.
  
  

Safety

• LP requires venting because it generates carbon dioxide and, potentially, lethal carbon monoxide. Electrical heaters require no venting and produce no gas emissions.
  
  

Efficiency

• Liquid petroleum heaters are usually 75 to 80 percent efficient: The heater itself will display its efficiency rating. The remainder converts to gas. Electrical heating is 100 percent efficient: All the energy goes on heating.
  
  

Heat

• Heat is measured in British Thermal Units (BTUs), the amount of heat required to raise 1 pound of water 1 degree F. Electricity is measured in kilowatt-hours. According to the U.S. Energy Information Administration, 1 kWh is equivalent to 3,414 BTUs, while 1 gallon of propane provides 91,333 BTUs.
  
  

Price

• 91,333 divided by 3,414 is 26.75. If LP costs $3.50 a gallon, the equivalent of one kWh would cost $0.13 ($3.50 divided by 26.75 is $0.13084.) Assuming your LP heater is 80 percent efficient, the cost increases 20 percent to $0.156. If electricity is less than $0.156 per kWh, electricity is cheaper.