What type of system is heating your home? For that matter, what is powering that heat?

Whether you are purchasing, upgrading, or simply maintaining your home, these and related questions are of critical concern. They are critical, dear reader, because presumably you are keen on having a system that is clean, efficient, durable, right-sized for your home and lifestyle, and finally, efficient both in terms of cost and energy consumption.

There are various types of heating systems out there, and depending on type, each can be powered (or fueled, as it is) using different sources. The following post breaks down what those systems are, their respective benefits and shortcomings, and the kinds of power that keep those systems humming, for better or worse.

Heating Systems and What Fuels Them

The main types of heating systems throughout most U.S. homes include forced-air systems, electric heating systems, radiant systems, radiant floor systems, solar heating systems, and wood and pellet combustion systems.

Each of these systems will invariably use a boiler, furnace, or heat pump to generate heat. The latter is fast gaining traction in many housing markets across all climate zones, both warm and cold, but heat pumps remain a distant third behind furnaces and boilers.

Forced-air central heating systems transfer heated air, using an electric blower, through a series of ducts, vents, or plenum spaces within the home. The most common systems that use forced-air distribution are furnaces, which is fueled by natural gas, propane, oil, or electricity; and heat pumps, which transfers outside heat into the home. Of those two, air-source electric heat pumps (both ducted and ductless mini-splits) are far more efficient, considerably cleaner, and less noisy than furnaces.

The list of advantages of having gas- or oil-powered, greenhouse gas-emitting furnaces has grown smaller since the advent of modern-day heat pumps. While heat pumps have been around for more than half a century, only in recent decades have they claimed greater market share, owing to newer models’ efficiency in colder climates, smart home integration capabilities, and much more. (By some estimates, heat pumps will account for 90% of the HVAC and water heating market by 2040 in several states, including California and New York.) Still, for homeowners who want added insurance, particularly in cold climates, many people opt for dual-fuel heating systems by combining a furnace (or boiler) with a heat pump.

Regarding heat pumps, electric heating is a great alternative to systems that use combustion appliances. But it’s not just limited to air-source heat pumps. Electric resistance heating systems, for example, are energy efficient and a decent option in areas where the electricity mix favors renewables (solar and wind) over coal, gas, and oil. The resulting resistance heat can then be supplied by centralized forced-air electric furnace or individual room heaters, including electric baseboards, wall heaters, or space heaters. However, heat pumps will usually be preferable to electric resistance systems because they use up to 50% less electricity.

Solar heating systems are in fact hybrid systems that require combining a solar power source with a traditional electric heater. In one example, solar energy from a photovoltaic panel array is channeled into a heat pump and its compressor, which then circulates warm air throughout the home. This method is highly efficient and will save you money over the long term. But depending on where in the country you live, the upfront costs of installing such a system may become a deterrent.

Radiant heating in a home is usually recognizable by one of two devices: hot-water baseboards or an old-fashioned steam radiator. In each case, the heating source is likely a gas- or oil-burning boiler. But instead of furnaces, which distribute air, radiant heat is created by channeling hot water (or steam, in the case of radiators) throughout the home using a web of pipes. Such systems are certainly efficient and often require little lag time between adjusting one’s thermostat and the delivery of heat.

Another popular device that delivers radiant heating is a hot water radiator, which is superior to its hissing steam predecessor in just about every way. The hot water option is low maintenance, less noisy, energy efficient, and creates zero atmospheric humidity.

Depending on the size of your home, one of two boiler types will meet most people’s needs: a systems boiler or a combination (aka “combi”) boiler. The first is typically reserved for larger homes with greater hot water demands, and thus requires a large hot water tank or cylinder. Combi boilers, on the other hand, are smaller and energy efficient, and therefore ideal for small and medium-sized homes.

Radiant floor heating, aka underfloor heating, is a method that traces its roots back not in decades or even centuries, but millennia. The Ancient Romans employed radiant central heating using a subfloor system called a “hypocaust” (translated from the Ancient Greek, meaning “under-burnt”), in which a building produces heat – via a wood-fired furnace – and circulates the radiant hot air (and gases from the combustion) under the floor and throughout the walls.

Nowadays, of course, such systems are safer and more efficient, and use hot water and run off boilers just as other modern radiant systems do. The obvious downside to radiant flooring is that they can be high maintenance, since any repairs will require the removal of flooring, and are expensive to install. However, radiant flooring systems are extremely space efficient in terms of heat distribution, emit heat at low temperatures, and are versatile. For instance, if you have existing underfloor heating but want to swap out a fossil-fuel-burning boiler for something cleaner, like a heat pump, solar hot water system, or geothermal system, those can all work with radiant flooring. However, if you’re looking to install new radiant flooring that is air-heated and/or coupled with an electric power source, that is a luxury for which you’ll pay handsomely.

Wood and pellet heating, aka biomass heating, is still in use in many U.S. homes today, albeit almost exclusively in colder climates and not nearly to the extent of forced air and radiant systems. The reasons for this are simple: they are high maintenance, expensive, require manual feeding and adequate storage space for the wood or pellets, and can release carbon monoxide and other pollutants if the stove or furnace is not working properly. That said, biomass is a renewable heating source and can prove very efficient within the right home. If you are pursuing this option, look to newer models that are certified under the 2015 New Source Performance Standards (NSPS), ensuring that the unit meets particulate emissions limits. Finally, while the look and feel of a wood furnace is alluring for many homeowners, make sure you are right sizing as well and purchasing a unit with a temperature range (in BTUs) and square foot limit that is appropriate for your home’s livable floor area.