Updated August 2023

How Much Oil Does a Furnace Typically Burn?

Most furnaces in the use burn natural gas, but oil-burning furnaces are still common in places where there is limited or no natural gas supply. The other option in these areas is a propane furnace, but oil furnaces are generally always cheaper to run and will usually last far longer. In either case, you will need to have your propane or oil tank filled on occasion to ensure you have enough fuel to continue running the furnace. One of the most common questions regarding oil furnaces is how much oil they typically use and how often the tank needs to be refilled, and here are all the answers you need.

Average Hourly and Daily Oil Usage

The exact amount of oil that a furnace will use in a day is largely dependent on how efficient the unit is and its size. In other words, how many BTUs of heat does the furnace produces? Efficiency is important since this will determine how long the furnace needs to run. The more efficient the unit is, the shorter each heating cycle will be and the fewer total hours the unit will run each day. Outdoor temperature is also an important factor since this will play a role in how frequently the furnace runs. The colder the temperature is, the more oil the unit will burn in a day.

On average, the furnace will usually burn anywhere from 0.7 to 2 gallons for each hour that it runs. In below-freezing temperatures, the furnace will often run for as many as eight to 10 total hours in a day. However, this normally only happens on the weekends or other times when the home is occupied throughout the day and the heating is left turned up. If you turn your heating down for the day while at work, you will typically only end up using around 8 gallons of oil in a day. If the outdoor temperature is in the 40s or 50s, your oil usage could drop to as little as 2 to 4 gallons a day.

Averaged out over the course of a winter, most oil furnaces will end up burning somewhere around 5 to 10 gallons a day. If you have a 550-gallon oil tank, this means you would want to have the tank refilled every six to eight weeks to ensure that you still have a sufficient supply for those freezing days.

Why the Age of the Furnace Is Important

Modern oil furnaces are far more efficient and burn much less oil per hour than older models. This has to do with the size of the oil-burner nozzle which dictates how much oil is sprayed into the furnace at a time. The nozzle works by instantly decreasing the pressure of the oil, which then turns it into a mist so that it can mix with air and burn properly. A larger nozzle on an older furnace will often result in the furnace burning about 2 gallons of oil an hour, while more efficient modern furnaces typically burn closer to 0.65 gallons an hour.

The Importance of Annual Furnace Maintenance

Having your furnace professionally inspected and maintained at least once a year is also essential for both how effectively the unit heats and how much oil it burns. Inspecting the unit will ensure it is free from any issues that could affect its performance and energy efficiency. The technician will also inspect the blower fan to make sure it is circulating air properly as this can also negatively impact the effectiveness of your heating system. If the inspection does reveal any problems, you can then have the issue repaired so that the furnace works properly once again.

The technician will also make sure that the furnace’s heat exchanger is still in good shape and not cracked. A cracked heat exchanger will lead to the furnace producing much less heat. That being said, the bigger issue is that it will allow carbon monoxide to escape out into the supply ductwork and then be circulated throughout the rest of the home.

Another important part of maintenance is cleaning all of the furnace components. Dirty furnace burners are a common problem caused by a lack of regular maintenance. When the burners become overly dirty, they will often prevent the oil from combusting fully. This will lead to the furnace producing less heat at a time. Because less heat is produced, the length of each cooling cycle will increase, leading to higher oil usage.

My Guy Heating and Air, LLC is a full-service HVAC company that serves residential customers in Mead, Boulder, and the surrounding areas. Our certified technicians specialize in furnace inspections, maintenance, repairs, and installation. We also work on cooling systems and indoor air quality equipment. Contact My Guy Heating and Air, LLC today if you have any questions or need any heating or cooling service.

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