- Wood pellet furnaces efficiently burn biomass, such as agricultural waste or scrap wood. They are ideal for homes in rural or remote areas with abundant biomass and access to wood pellets but without easy access to natural gas or heating oil lines. Pellet furnaces are typically less efficient and may be more polluting than other furnaces.
- All-electric furnaces are the only models that reach 100 percent efficiency. However, the higher cost of electricity in most areas makes them cost-prohibitive. Moreover, standard coal-fired electric plants are closer to 30% efficiency, so it is probably better for the environment to efficiently and directly convert cleaner-burning natural gas to heat.
- Solar-powered electric furnaces in off-grid homes may be the exception to the no-electric rule. However, they require large solar arrays, which are expensive. They also require backup power sources because sunlight hours are shortest in winter, when you need the most heat.
- Geothermal furnaces are another renewable option with zero emissions and high efficiency. They draw underground heat and distribute it throughout the house. Like solar power, geothermal power is free, but it involves sizable up-front costs.
Look for highly efficient furnaces. They can pay for themselves in short order through lower utility bills. Also consider renewable power options for some circumstances.