Which Costs More to Run: A Boiler or a Furnace?

Energy cost is a significant factor when choosing the best heating system for your home. Unlike other seasons, winter demands nonstop HVAC operation, which means your system’s efficiency, fuel type, and usage habits directly influence your monthly bills. Boilers and furnaces both keep your home warm, but they do it in very different ways, and those differences show up on your utility statement. Here’s a comprehensive breakdown of boiler vs furnace cost to run.

Furnace Heating Costs

A furnace is a forced-air system. It works by transferring heat to air, and then a blower fan pushes that heated air through the ductwork and out via the supply vents.

The heating cycle typically begins with a signal from the thermostat. When it detects that indoor temperatures have dropped below your set point, it sends a command to the furnace’s control board. The control board first activates the inducer motor to create a draft, clearing out any residual combustion gases and preparing the system for ignition. Next, it energizes the ignitor, which lights the gas burners.

The flame produced heats the heat exchanger. The heat exchanger consists of metallic tubes designed to transfer heat to the indoor air safely. Hot combustion gases flow inside these tubes, while cooler air from your home passes over the outside surface. As the air absorbs heat from the metal, it warms up and is then pushed through the ductwork by the blower fan.

Factors Influencing Operating Costs of Furnaces

Almost everything about your furnace affects operating costs. Here are the major players it includes.

Fuel Type

Furnaces that use propane as their energy source are generally more efficient than natural gas or oil. Propane has a higher energy density, meaning it produces more heat per unit of fuel. However, natural gas is often the more economical choice because of its widespread availability and lower cost in most regions.

Electric furnaces are typically discouraged unless electricity is significantly cheaper than fuel in your area. While electric units are nearly 100% efficient at converting electricity into heat, the cost of electricity per BTU is usually much higher than that of natural gas or propane. This often results in noticeably higher monthly heating bills, especially in colder climates where the system must run continuously.

Ductwork

After heating the air, the furnace distributes it to your various rooms through the duct system. The quality of those ducts directly impacts operating costs. If the ducts are properly designed, correctly installed, and well‑insulated, your energy costs stay lower because more of the heated air reaches its intended destination.

However, if the ductwork leaks, is undersized, poorly insulated, or runs through unconditioned spaces, a significant portion of heated air can escape before it ever reaches your living areas. Even small leaks can add up, forcing the furnace to run longer and consume more fuel to maintain the desired temperature.

AFUE Rating

An AFUE (Annual Fuel Utilization Efficiency) rating is a metric that shows how much of the furnace’s fuel is converted into usable heat. A system with an 80% AFUE rating means that 80% of the fuel consumed becomes heat for your home, while the remaining 20% is lost through the exhaust or inefficiencies in the combustion process.

A system that converts more of its fuel into usable heat will have a lower operating cost. Modern furnaces can be up to 98.5%. The higher the rating, the better.

Blower Motor Electricity Use

Even though furnaces primarily rely on fuel for heat, the blower motor uses electricity to circulate warm air throughout the home. Older PSC (permanent split capacitor) motors consume significantly more electricity than modern ECM (electronically commutated) motors.

ECM motors are more efficient because they use smart electronics to adjust airflow precisely to the home’s heating demand. When you only need to raise the temperature by a few degrees, the motor automatically slows down, using far less electricity than a traditional single‑speed blower. This is why ECM motors are commonly known as variable‑speed motors.

Boiler Heating Costs

Boilers follow a similar overall heating process to furnaces, but the key difference lies in the medium and method of heat transfer. While furnaces heat air, boilers heat water over their heat exchanger. Also, instead of distributing warm air through ducts, boilers deliver heat through a network of pipes that supply either hot water or steam to radiators, baseboards, or in‑floor heating systems.

Factors Affecting Operating Costs of Boilers

Boilers run on natural gas, propane, oil, and electricity just like furnaces. Therefore, the energy density of these fuels affects them in the same way. The following are specific factors that affect its operating costs.

Quality of Installation

Using water as the medium for heat transfer presents more challenges than heating air, which makes installation quality a major factor in boiler operating costs. Boilers require correctly sized piping, proper pump selection, balanced zones, and careful attention to pressure, flow rate, and venting. If any part of the system is improperly installed, the system may run longer, cycle more frequently, or struggle to deliver even heat. All of these issues increase energy consumption and raise monthly heating bills.

AFUE Rating

Just like furnaces, boilers are rated by AFUE. The higher this rating is, the lower the operating costs will generally be.

Water Quality

Boilers rely on clean, properly conditioned water to transfer heat efficiently. If you have a hard water problem or your supply contains sediments, your operating costs will be higher.

Distribution System Efficiency

The network of pipes supplying hot water must be well‑insulated, and the heat emitters strategically distributed throughout the home. If the heat emitters (baseboards, radiators, etc.) leave cold spots in a room, the boiler will work harder to compensate for those inefficiencies, consuming more energy as a result.

Also, the radiators should not be obstructed by furniture, curtains, or other objects. Radiant heat needs a clear path to flow into the room. When heat is blocked, the space warms more slowly, causing the boiler to run longer and use more fuel to reach the desired temperature.

Which Is Better?

Both boilers and furnaces do an excellent job of maintaining comfortable temperatures during the winter. Ultimately, efficiency comes down to the quality of the system you purchase, the quality of the installation, and the level of maintenance and care it receives. However, when comparing systems with similar features and efficiency ratings, a boiler will generally cost less to run over time.

This advantage stems from three important factors: water’s higher heat‑carrying capacity, the efficiency of radiant heat, and the absence of ductwork. Water can hold and transport far more heat than air. Because of this, boilers can move large amounts of heat using relatively small temperature changes and lower pumping energy.

Radiant heat warms objects and surfaces directly, which creates a more even, consistent comfort level. Since radiant systems don’t rely on blowing air, they avoid the temperature swings and heat loss associated with forced‑air systems.

Contact Black-Haak for More Information

You can trust our experts at Black-Haak to install the best boiler or furnace for your home. We not only supply high-quality, efficient systems but also offer flexible financing options for qualifying clients to make access to reliable heating more affordable.

Contact Black-Haak for professional heating installation and maintenance in Greenville.