A conventional heating system generates warmth by burning fuel or using electric resistance, then distributes that heat throughout your home via ducts, pipes, or baseboards. This distinguishes it from newer alternatives like heat pumps, which transfer heat rather than creating it. The two most common conventional setups in North American homes are forced air furnaces and boiler-based (hydronic) systems, and each works quite differently.
Forced Air Systems
Forced air is by far the most common heating system in modern North American homes. A furnace burns fuel or heats electric coils, and a blower fan pushes warmed air through a network of ducts to registers in each room. A separate set of return ducts pulls cooler air back to the furnace to be reheated, creating a continuous loop.
The heating cycle works like this: your thermostat signals the furnace to fire up its burners (or, in an electric model, its heating coils). Air passes over a heat exchanger, absorbs the warmth, and the blower sends it through your ductwork. Exhaust gases from combustion vent outside through a flue in the roof or a side wall. The whole cycle repeats until your home reaches the set temperature.
One practical advantage of forced air is that the same ductwork can serve a central air conditioner in summer, so you get year-round climate control from one distribution system. The downside is that ducts can leak conditioned air, collect dust, and distribute allergens if filters aren’t maintained.
Boiler and Hydronic Systems
Instead of blowing warm air, a boiler heats water and circulates it through pipes to radiators, baseboard units, or radiant floor tubing. The key components are the boiler itself, a circulator pump that moves hot water through the piping, and heat emitters (the radiators or baseboards) that release warmth into each room. Once the water gives up its heat, it flows back to the boiler to be reheated.
Older boiler systems use steam rather than hot water. Steam rises through pipes to cast iron radiators without needing a pump, then condenses back into water and returns to the boiler by gravity. These systems are still found in many older homes, particularly in the Northeast. A more modern variation is the hot water baseboard system, where heated water flows through finned copper pipes along the base of walls, warming the air around them.
Boilers tend to provide more even, comfortable heat than forced air because they don’t create drafts or blow dust around. They also run more quietly. The tradeoff is that a boiler system can’t double as air conditioning, so you’d need a separate cooling setup.
Fuel Sources and Energy Content
Conventional systems run on natural gas, propane, heating oil, or electricity. Natural gas is the most widely used and generally the least expensive per unit of heat delivered. At roughly 100,000 BTUs per therm, natural gas in an 85% efficient furnace costs around $8.24 per million BTUs, based on Oklahoma State University Extension data. Propane contains about 91,600 BTUs per gallon and costs roughly three times more per unit of useful heat. Heating oil packs the most energy at around 139,400 BTUs per gallon but runs at about 80% efficiency in a typical system.
Electric resistance heating converts energy at 100% efficiency (every kilowatt-hour becomes heat), but electricity is expensive enough per BTU that it often costs the most to operate. At $0.11 per kilowatt-hour, electric resistance heat runs about $32 per million BTUs, nearly four times the cost of natural gas. Your local utility rates and fuel prices will shift these numbers, but the general ranking holds in most regions: natural gas is cheapest, followed by heating oil, propane, and electric resistance.
Efficiency Ratings
Furnace and boiler efficiency is measured by AFUE, or annual fuel utilization efficiency. This percentage tells you how much of the fuel’s energy actually becomes usable heat. An 80% AFUE furnace converts 80 cents of every fuel dollar into warmth, with the other 20 cents lost through exhaust.
Standard efficiency furnaces operate around 80% AFUE, while high-efficiency condensing models reach 90% to 98%. The U.S. Department of Energy has finalized new standards taking effect in late 2028 that will require non-weatherized gas furnaces to achieve at least 95% AFUE. This means nearly all gas consumed will convert to heat for your living space, and manufacturers will phase out the older 80% models for new installations.
Performance in Cold Climates
Conventional heating systems have a distinct advantage in harsh winters. Gas furnaces produce high-temperature heat regardless of how cold it gets outside, making them well suited for northern climates. In contrast, heat pumps pull warmth from outdoor air and become less effective as temperatures drop. In colder regions (zones 4 and above on the DOE climate zone map), a 95% efficient gas furnace outperforms even ENERGY STAR-rated heat pumps. Oil furnaces similarly provide reliable comfort when temperatures drop well below freezing. This is the primary reason conventional systems remain the standard in cold-weather areas.
Installation Costs
As of 2025, a gas furnace installation (including the unit, thermostat, and venting) typically runs $3,000 to $6,500. Electric furnaces tend to fall at the lower end of this range since they don’t need gas lines or combustion venting. A gas condensing boiler installation, including the unit, flue, and controls, ranges from $3,500 to $8,500. Boiler installs cost more partly because the piping and radiator infrastructure is more complex than ductwork.
If your home already has ductwork, replacing a furnace is straightforward and stays near the lower end of the range. Converting from one system type to another, say from radiators to forced air, involves major work and significantly higher costs because you’re installing an entirely new distribution system.
Lifespan and Maintenance
Gas furnaces last 12 to 15 years on average. Electric furnaces hold up longer, typically 20 to 30 years, because they lack combustion components that corrode and wear. Boilers are the most durable conventional option, lasting 15 to 30 years depending on the type and how well they’re maintained.
Keeping a conventional system running well requires a few recurring tasks. For forced air systems, checking or replacing the air filter monthly is the single most important thing you can do. A clogged filter restricts airflow, forces the blower to work harder, and drives up energy bills. ENERGY STAR recommends inspecting filters monthly throughout the heating season. Beyond filters, an annual professional tune-up should include checking gas or oil connections, verifying gas pressure and burner combustion, and inspecting the heat exchanger for cracks. A cracked heat exchanger can leak carbon monoxide into your living space, so this isn’t optional maintenance.
Boiler maintenance is less hands-on for homeowners but still needs annual professional attention. Technicians check water pressure, inspect the circulator pump, test safety valves, and look for leaks in the piping. Cast iron radiators occasionally need bleeding (releasing trapped air) to heat evenly, which you can do yourself with a radiator key.
How Conventional Systems Compare to Heat Pumps
The main alternative to conventional heating today is the heat pump, which moves heat from outside air (or the ground) into your home rather than generating it through combustion. Heat pumps can be two to three times more efficient than resistance electric heating because they’re transferring energy rather than creating it. In mild climates, they often cost less to operate than gas furnaces.
Conventional systems still hold an edge in several situations. They deliver higher-temperature air (typically 120°F to 140°F from a furnace, versus 90°F to 100°F from a heat pump), which feels warmer coming out of the registers. They maintain full output in extreme cold, while standard heat pumps lose capacity as outdoor temperatures fall. And in areas where natural gas is cheap and electricity is expensive, a gas furnace costs significantly less to run. Many homeowners in cold climates now pair a heat pump with a gas furnace in a dual-fuel setup, using the heat pump in moderate weather and switching to the furnace when temperatures plunge.