How Much Electricity Does A Gas Furnace Use

According to Energy Star, an energy-efficiency program run by the U.S. Department of Energy, heating and cooling expenses make up staggering 42% of the energy bill for an average household. No wonder, we are always on the lookout for cheaper ways to cool or heat our homes.

Nearly half the U.S. households rely on natural gas, as a cheaper alternative for heating. If you are also thinking about investing in a gas furnace, read on. You will find out how to calculate the power consumption and cost od a furnace, what factors affect its running costs, and compare gas and the electric furnace for heating.

How Does A Gas Furnace Work

There are many heating options from which to choose for your home. There are other alternatives to gas furnaces, such as an electric furnace or a convection heater. Each option will have strengths and weaknesses, so it can be difficult to decide which is the best for your family. 

Before we jump to calculating the energy usage, let’s take a look at how does a gas furnace work.

A furnace consists of a few main parts:

  • A thermostat to communicate with your HVAC unit
  • Burners (metal tubes) through which the natural gas travels
  • Heat exchanger that warms the air inside of the furnace
  • The blower motor directs air towards the heat exchanger and then out throughout your house

How does it work?

Step 1: Your thermostat tells the furnace that the temperature dropped.

Step 2: A valve opens allowing the natural gas to begin flowing towards the burner.

Step 3: The burner’s ignition heats the gas, which in turns warms up the air flowing through it

Step 4: The warm air exists the ductwork and enters your home, it forces the cold air into the furnace and the process starts again

Factors That Affect Running Costs

So what are the factors that impact how much energy does the above process consumes and ultimately, the amount that finds its way onto your utility bill?


Gas furnace efficiency is nothing more than a measure of how good your furnace is at converting gas into heating energy (expressed in British thermal units) and is reflected as a percentage (in annual fuel-utilization-efficiency or AFUE rating). Naturally, the higher the number, the more heat you’ll get for less cost.

The minimum allowed gas furnace efficiency is 78% and some new models achieve 97 percent, near-total efficiency. Of course, the higher the efficiency, the more such furnace would cost so it’s important to find a balance.

An average U.S. household uses between 50 million and 150 million BTUs in heating each winter, so depending on which end of the scale do you find yourself, the energy efficiency of your device should reflect that.

Your Cost of Heating

According to the U.S. Energy Information Administration, the average residential price for thousand cubic feet of natural gas is $9.86. However, the cost that residents in the individual U.S. states pay will vary significantly. For example, Texas residents will pay $9.39 while households in California will be stuck with a price as high as $13.69.

If your current heating price is on the higher end, there is good news! Thanks to energy deregulation, you can switch gas and electricity providers by shopping for cheaper energy prices.

Cost to Run a Gas Furnace

So finally, how can you calculate the running costs of your gas furnace?

Let’s assume that your household uses 100 million BTUs per year. However, that’s a really high number to work with, so go ahead and divide that by 100,000 to arrive at 1000 therms of gas.

Let’s say you live in Texas, where natural gas costs $9.36 per thousand cubic feet or 90 cents per therm.

Now let’s say you have a device with a high gas heat efficiency of 90%. The way to think about it is that 10% of the energy consumed by your furnace will not result in generated heat, so your actual energy cost per therm of gas will be $0.9 x 1.10 = $1.

That means that your annual heating expenses will be approximately 1000 x $1 = $1000 dollars, approximately $80 per month, or $2.7 dollars per day.

Of course, the above calculations are based on assumptions, but hopefully, they provide you with a useful template to calculate your own furnace energy costs.

Is It Cheaper To Heat With Electricity Or Gas?

When searching for the best appliance, you might have come across a different type of furnace – an electric furnace; and wondered which is better. Here are some pros and cons of both.

The electric furnace cost can easily be only half of what you will pay for a gas one. The reason for that is the installation cost – when dealing with the combustive element, such as gas, everything must be sealed perfectly to prevent leakage of carbon monoxide, usually requiring specific equipment and skills.

An electric furnace is the more efficient of the two. Its electric heat efficiency rating might be as high as 100 percent.

However, despite the higher average efficiency and lower installation costs of electric furnaces, the running costs will be higher due to the higher average costs of electricity. On the other side, you can shop around for cheaper electric price per kWh to lower your electric bill.

The electricity usage of electric furnaces ranges from 10 kilowatts to 50 kilowatts. Let’s say you own a 20 kWh electric furnace which you use for 2 hours per day.

If you live in Texas and you haven’t yet switched electric suppliers, you are paying the standard electricity tariff of 11.85 cents per kilowatt-hour.

Your electricity cost per hour can be calculated as 20 kWh x .1185 = $2.37 per hour or $4.74 per day. If your energy usage is consistent, that’s a monthly cost of $144.19.

Since heating and cooling make up almost half of your energy bill, you should be able to estimate your monthly heating costs and how to reduce them. Hopefully, this article has helped you understand how to calculate how much does it cost to run a gas or electricity furnace. If you are interested in further exploring the topic of heating costs, you can read our guide on how much does it cost to run a portable electric heater next.

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