Electric Furnaces: How They Work and Understanding the Pros and Cons

Electric Furnaces: How They Work and Understanding the Pros and Cons

Electric furnaces are a common heating option in California. An electric furnace can effectively keep your home warm as long as the outside temperature doesn’t get too cold. It will also tend to cost less to install than most other heating options. Despite the lower price, an electric furnace isn’t always the best option, as your heating costs will almost always be higher with this type of unit. To help you understand why this is, here’s an overview of how electric furnaces work and how they compare to other heating options.

How Electric Furnaces Produce Heat

Electric furnaces and gas furnaces both use a heat exchanger that transfers heat energy to the cool air flowing through the furnace. The difference between the two is how they produce heat and how the heat exchanger works. Gas furnaces obviously burn gas to produce hot flames. The heat from the flames rises up into a metal heat exchanger that then captures much of the heat. When cool air flows over the heat exchanger, all of the heat the exchanger stores is transferred from the metal into the air.

Electric furnaces typically have between three and six electric resistance coils or heating elements located inside the heat exchanger. Each heating element is made from a metal wire that’s tightly wrapped into coils. The metal wires in an electric resistance heating element are similar to the wires inside of a toaster. As electricity flows through the wires and meets resistance, the wires almost instantly heat to the point where they’re red hot and glowing. As cold air moves through the heat exchanger, the heat radiating from the resistance coils is naturally absorbed by the air, instantly making it much hotter.

The reason that the electric resistance coils produce heat has to do with what happens when electricity flows through or meets metal. Electricity always causes any metal to quickly become extremely hot. This is because metals are resistant to the flow of electricity. Electricity is simply the movement of electrons between different atoms. When electricity flows through any type of metal, the electrons meet resistance and collide with ions in the metal. These collisions produce lots of heat, causing the metal to quickly become hot.

How Much Energy Does an Electric Furnace Use?

Electric furnaces are always more efficient than gas furnaces. They’re also cleaner and better for the environment since electric heating doesn’t produce carbon emissions like burning natural gas or propane does. The energy efficiency of any type of heating is measured in terms of how many units of heat energy the unit produces compared to how many units of energy it uses.

The energy efficiency of modern gas furnaces ranges between 80% to 98.5%. A gas furnace that’s 80% efficient produces eight units of heat energy for every 10 units of gas it burns. The other two units of energy the unit uses are wasted or lost, which is because the metal heat exchanger can only absorb so much heat from the hot fumes flowing through it. Some latent heat always remains in the fumes when they rise out of the heat exchanger and flow up through the exhaust flue, which results in some of the heat energy being wasted.

Electric furnaces and all other types of electric resistance heating like space heaters and baseboard heaters are always 100% efficient. This means that the electrical energy they use is always directly converted into heat energy at a one-to-one ratio. In other words, electric resistance heaters produce one unit of heat energy for every single unit of electrical energy they use. This is because all of the heat released by the resistance coils in an electric furnace remains trapped within the heat exchanger and naturally flows out into the air, so there’s no energy waste like there is when burning gas. Space heaters and baseboard heaters don’t have a heat exchanger, but all of the heat emanating from the coils still flows out into the surrounding air.

Despite being more energy-efficient, an electric furnace will almost always cost more to operate than a similar sized gas furnace. This is partly because electricity rates tend to be quite a bit higher than natural gas rates in most places. The other reason is simply because electric furnaces use a huge amount of electricity.

In California, you typically need a unit that produces somewhere around 30 to 35 BTUs of heat for each square foot in your home to heat it effectively. A 1,500-square-foot house would typically need a minimum of 45,000 BTUs of heating. This means that you’d normally need between a 15- and 20-kilowatt electric furnace to ensure your home stays sufficiently warm. To cool the same size house in your area, you’d normally need a 3- or 4-ton air conditioner. Depending on its energy efficiency rating, this size of AC unit would normally use anywhere between 2.5 and 5 kilowatts per hour (kWh).

Comparing the kWh difference between an electric furnace and an air conditioner easily shows you just how much energy an electric furnace uses. The fact that the winters in California tend to be fairly mild means that an electric furnace will never run nearly as much as an air conditioner. Nonetheless, when an electric furnace does need to run, it will use far more electricity than an AC unit would if it ran for the same amount of time.

Comparing Electric Furnaces and Heat Pumps

Converting your home to electric heating can definitely help to lower your carbon footprint, but opting for a heat pump will always be the better and more energy-efficient option compared to an electric furnace. Heat pumps also run on electricity, but unlike an electric furnace, they don’t just convert electricity into heat. Instead, they use the electricity to move heat from outside into the house using refrigerant.

Heat pumps can heat and cool, and they work just like any other type of air conditioner when cooling. However, they can also switch so that instead of using the refrigerant to remove heat from the home, the refrigerant removes heat from the air outside and releases it indoors. This is possible due to a heat pump’s expansion valve and reversing valve.

The reversing valve allows a heat pump to reverse the direction of the refrigerant flow. Instead of having cold refrigerant flowing into the house as the unit does when cooling, it switches so that cold refrigerant flows through the coil in the heat pump outside the home. That way, the system can capture heat from the outdoor air and pull it inside the building.

As refrigerant moves through the heat pump, it first absorbs enough heat from the air that it changes from a cold liquid to a hot liquid. The semi-heated refrigerant then passes through the expansion valve, which causes the refrigerant to boil and instantly change into a superheated gas. As the heated gas refrigerant moves inside the home and enters the coil in the air handler, it automatically releases all of the heat and instantly raises the temperature of the air moving through the ductwork and flowing over the coil.

The fact that heat pumps use electricity to capture and transfer heat instead of just converting it directly into heat makes them far more energy-efficient. Although the energy efficiency of a heat pump does start to decrease in colder weather, a heat pump will still typically be around 60%-70% more energy-efficient than an electric furnace. The fact that a heat pump can also cool your home provides an added benefit. All you’ll need is one unit to keep your home cool in the summer and hot in the winter instead of needing to install and maintain a furnace and a traditional air conditioner.

Crystal Blue Heating, Plumbing and Air specializes in all types of heating installation, and our team can help if you’re looking to install a heat pump or any type of furnace. We also offer professional heating and air conditioning maintenance services. Plus, we can repair any issue your HVAC system may have. To learn more about your heating options or to schedule any HVAC service in the Sacramento area, give us a call today.

How a Gas Furnace Heats Your Home

How a Gas Furnace Heats Your Home

When you adjust your thermostat, your furnace kicks on and your house warms up. The entire process behind how and why this happens is often ignored. Ultimately, this can lead to a reduction in your unit’s effectiveness and efficiency. Discover how a gas furnace heats your home, the major components in the furnace, and the differences that exist between models.

Generating Heat

What sets furnaces apart from other heating devices is how they generate heat. In most cases, the furnace will burn fuel to create heat, usually either natural gas or propane. In some cases, you may have an electric furnace, which uses electrical resistance to create heat.

For fuel-burning furnaces, the heat that’s created comes in the form of the exhaust that’s produced when the fuel burns. The furnace then has to transfer that heat from the exhaust to the circulating air without mixing toxic fumes into your home.

Transferring Heat to the Air

Once the furnace produces heat, it flows into the heat exchanger, which transfers the heat. The hot exhaust flows inside the tubes of the heat exchanger, which absorbs the heat, warming the outside of those tubes.

The air moving through the furnace then flows over the outside of the heat exchanger, absorbing the heat. The warmed air then moves back into your home. As long as the heat exchanger isn’t cracked or damaged, the exhaust never mixes with the air circulating through the furnace.

Distributing Heat Around Your Home

Once the warm air flows out through the supply vents, it has to circulate around your home to be distributed evenly. The system creates both positive and negative air pressure to create circulation in your home. The positive pressure occurs at your supply vents, while the negative pressure occurs at the return vents. It’s this circulation that then causes the warm air to distribute instead of staying at the location of the supply vents.

Critical Parts of a Furnace

Now that you understand how a furnace works, it’s time to explore the components that make it happen. This will help you identify when you have a problem, what it could be, and the possible solution to solve it.


Most people recognize this as the device that’s mounted to the wall where you set your temperature. It acts as the brain for the furnace, signaling when to initiate and terminate heating cycles.

Control Board

While the thermostat is the brain of the furnace, the control board directs what happens and when. This takes all of the inputs as the furnace cycles from one phase of heating to another. For instance, it’s the control board that monitors the heat produced and starts the circulating fan when enough heat has built up.

Draft Inducer Fan

For the furnace to work efficiently, there has to be constant air movement through the burn chamber and out through the flue. This provides the right mixture of air for the fuel to burn efficiently, along with moving the exhaust out. While this becomes a sustainable cycle once the system heats up, it needs a little help while warming up. The draft inducer fan provides that assistance at the beginning of each cycle.


Furnace burners aren’t that different from gas grill burners. They provide a place where the gas flows out and burns safely, producing the hot exhaust, which will then flow through the rest of the system properly.


The furnace has to ignite the fuel at the beginning of each heating cycle, and so it has an igniter of some form. Older models had a standing pilot light, which was a small flame that constantly burned. However, newer models have primarily gone to an electric igniter so that there isn’t a constant use of fuel for a pilot.

Heat Exchanger

The heat exchanger is a series of tubes that conduct the hot exhaust from the burn chamber to the exhaust flue. The exhaust heats the outside of the exchanger, and the circulating air then flows over the outside of those tubes, absorbing the heat.

Circulating Fan

The circulating fan does exactly what it says it does: circulates air. It draws air in through the cool air return, then pushes it back out through the supply vents. It’s comprised of a circulating fan wheel and the circulating fan motor, also called the blower motor.


The flue is the pipe that directs the exhaust from the heat exchanger to vent outside your home. You’ll see it as a pipe that comes off the top of your furnace. From outside, you’ll see it come through the roof, usually with a crown or cover over it. If you have a high-efficiency furnace, your flue may come through the side of your home rather than through the roof.

Upper Limit Switch

Since your furnace is burning fuel to create heat, it’s important that the temperature is properly controlled. An overheated furnace can cause a cracked heat exchanger, which will allow carbon monoxide to leak out. The upper limit switch monitors the temperature in the supply plenum and shuts down the furnace if it gets too hot.

Flame Sensor

The flame sensor resides inside the burn chamber and is responsible for ensuring that there’s sufficient heat to ignite the fuel. This sensor gets dirty over time and will need routine cleaning to continue operating properly.

Air Filter

An air filter is one of the most critical components for keeping your HVAC system working effectively. It keeps airborne contaminants out of the system so that they don’t clog up the internal components. However, a neglected air filter will cause an airflow restriction that hinders the efficient operation of the system.

Blower Motor Capacitor

The blower motor requires a large electrical charge to start working at the beginning of the heating cycle. To prevent an instantaneous large draw on your home’s electrical system, the furnace has a capacitor to deliver the charge. This is a special electronic device that stores and quickly releases a large electric charge.

Differences in Furnace Models

There are several types of furnaces, each with differing efficiency ratings. Standard models have a single-stage burner, a fan, and only one heat exchanger. Higher-efficiency models have a modulated burner, which changes how much gas it’s burning. They’ll also have a variable-speed fan to adjust how much air it’s circulating. Finally, if you have a high-efficiency condensing furnace, you’ll have a second heat exchanger to draw even more heat from the exhaust.

Crystal Blue Plumbing, Heating & Air has been a trusted service provider around Loomis since 1976. Our team takes pride in providing AC and heating installation, maintenance, and repair, together with duct repair and replacement, indoor air quality solutions, and a wide range of residential plumbing services. Call us today to schedule your furnace repair or replacement consultation with one of our experienced NATE-certified technicians.