Small space heaters are typically used when the main heating system is inadequate or when central heating is too costly to install or operate.
Solar air collectors can be installed on a roof or an exterior (south-facing) wall for heating one or more rooms. Factory-built collectors for on-site installation are available, and do-it-yourselfers may choose to build and install their own collector.
Gas-fired space heaters include wall-mounted, freestanding, and floor furnaces, and are most useful for warming a single room or contiguous areas. Better models use “sealed combustion air” systems, with pipes installed through the wall to both provide combustion air and carry off the combustion products. A warning: Ventless gas heaters can expose occupants to combustion by-productss and oxygen depletion, as can stand-alone kerosene, propane, and oil heaters. Because of these hazards, at least five states prohibit vent-free heaters in homes, and many individual cities have banned them as well.
Electric space heaters. Portable (plug-in) electric heaters and electric baseboard units convert electricity directly into heat. Generally, these systems have low or no installation costs. With baseboard heaters, individual room thermostats can be installed so you can turn down the heat in rooms that aren’t being used. Operating costs, as for all resistive heaters, are generally very high.