Coil-fueled boilers typically extract roughly 86 to 88 percent of the energy of burned coal. However, various regulations and the convenience of other types of boilers make other fuels far more popular options.
While coal was once a mainstay for heating homes, even clean-burning technology releases a significant amount of particulate matter in the air. Burning coal is viewed as a threat to public health, leading to bans on the use of coal as a heating fuel in much of the developed world. Many coal boilers have been converted into oil and natural gas boilers over the years.
While the low cost of coal makes it competitive with natural gas, its transportation weight makes it expensive for small structures. As a result, coal is primarily used in power plants, which can often accept delivery by rail, reducing the transportation cost per pound of fuel significantly.
Oil and natural gas also require less maintenance to use. Coal generates ash when it burns, and ash must be disposed of safely to prevent a host of potential health issues. Residential areas usually do not provide areas to dispose of ash safely, making it nearly impossible for a home to rely on coal for heating. Coal-burning equipment also requires regular maintenance, further driving up its cost.