How efficient are nonelectric heaters?

Nonelectric portable heaters can be an efficient way to provide heat for a small room or to supplement inadequate heating in one room. Space heater capacities generally range between 10,000 and 40,000 Btus per hour, and commonly run on electricity, propane, natural gas and kerosene.

Propane, natural gas and kerosene provide heat but, when the heater is unvented, are not recommended for use inside the home because of the possible emission of dangerous gases. Electric space heaters are generally the most expensive and inefficient to operate, but they are the only unvented space heaters that are safe to operate inside your home. However, they still pose fire and burn risks and should be used with caution.