Generally, the three most inexpensive heating fuels are oil, propane and natural gas. Natural gas is considered the most inexpensive heating fuel, as of 2015, and trends show it could continue to be a low-cost option.
Oil is the most expensive of the four choices, so oil heat is not as competitive as it could be with other low-cost fuel options. Propane is slightly cheaper than oil, but it is not popular. Natural gas is the most popular heating fuel option, and analysts speculate that a large supply is available. Electricity, though not a gas, is another option to consider, depending on the situation, because of its generally low cost.