November 9, 2023

Heat Pump Services in St Louis, MO

How To Determine What BTUs Mean With Heat Pumps

Heat pumps are the most cost-effective heating and cooling systems on the market and a great option for new builds or for spaces that are being renovated. If you’re interested in a new heat pump system, you’ve probably noticed that these come with a BTU rating. What does this number mean? Why is it important? Does it matter which BTU rating you choose for your heat pump? You can find the answers to these questions and more below.

What Does BTU Mean?

BTU stands for British Thermal Unit, a universal method of measuring the amount of hot or cold air needed for heating or cooling a space. Heat pumps work by drawing heat in from the outside to heat your home and transferring heat out of a home to cool it.

These heat transfers are measured in BTU, or in other words, by how many thermal transfers happen per hour. The main factor for determining your heat pump’s BTU rating is the size of your home, but other factors like insulation, ceiling height, and heated appliances can change your BTU rating.

Why Is the BTU Rating Important When Choosing a Heat Pump?

You’ll need to know how many BTUs your home will require before installing a heat pump. You might think it’s a cost-effective solution to install a heat pump that has a lower BTU rating since lower-producing units are less expensive, but you’ll end up spending more money in the long run. A smaller system will struggle to heat or cool your home, leading to repair costs, a higher electricity bill, or both.

Similarly, you might think it’s wise to invest in a system that puts out several more BTUs per hour than your home needs. However, a system that is too large for your home can also cause strain on the heat pump. A larger system will heat or cool the area quickly but will also lead to constant shutoffs if it’s improperly matched to your square footage.

What Happens if the BTU Rating Is Too High or Low for My Home Size?

Compared to furnaces, which produce their own heat, heat pumps use a heat transfer system, which is much more cost-effective. In most cases, a heat pump is the most economical way to heat or cool a house, but only if you choose one with the appropriate BTU rating.

If your BTU rating is too high for your home, the heat pump reaches the correct temperature too fast. This might sound like an effective heating or cooling method, but heat pumps are designed to shut off once the house reaches the right temperature. Pumps are made this way to reduce costs. The problem is that sharp spikes in temperature will cause your home to quickly grow cold or hot again, causing the heat pump to switch on again. This rotation, known as short cycling, repeats itself constantly.

Turning on and off again will wear down the motor of the pump and decrease its longevity. You’ll always find yourself too cold or too hot because the pump is going through too many fluctuations and cannot reach a steady temperature.

During the winter, the pump won’t be able to stay running long enough to defrost the pump parts, leading to damage from ice and cold. In the summer, the pump won’t be able to remove moisture from the air when shutting on and off, leading to high humidity levels in your home.

When the BTU rating is too low for your home, the opposite effect occurs. A heat pump will have to run continuously at full capacity to try to reach the desired temperature. The motor will wear out faster than it should, leading to an expensive repair or replacement for your pump.

Aside from wear and tear on the heat pump parts, constantly running the system will increase your electricity bill. Heat pumps are installed to work with your home’s electrical system, and they will use more electricity if they’re running inefficiently.

Heat pumps work best when the system can transfer heat at a more moderate pace without hitting extreme highs or lows. In order to accomplish this, you’ll need to know what BTU rating works best for your home.

How Do I Know Which BTU Rating to Use for My Heat Pump?

A lot of factors go into knowing how many BTUs you will need, but the simplest method is to calculate BTUs using square footage. In most cases, 500 square feet will require at least one ton of heating or air conditioning capacity. One ton of capacity equals 12,000 BTUs. So, if your home is 2000 square feet, you’ll need a heat pump that can produce at least 4 tons or 48,000 BTUs.

Don’t forget to consider ceiling height in your calculations. Larger rooms with higher ceilings tend to be draftier, so you might need to purchase a system with more BTUs to properly heat the space.

If you prefer to install a ductless heat pump, you can use square footage as a guide for choosing the right unit. To measure the square footage of the room where you want to install the unit, simply take the length of the room and multiply it by the width. Take the sum and calculate how many tons of heating/cooling capacity you will need using the 500-square-foot rule as a guide. An 800-square-foot room, for example, will need between one or two tons, or 12,000 to 24,000 BTU.

If you’re unsure about how to measure square footage or you’re worried about choosing the wrong size pump, it’s a good idea to hire an HVAC professional to take a look at your home and help determine what size pump will work best.

Industry professionals might use the Manual J system to evaluate your home, which can give a more accurate BTU estimate than square footage alone. Manual J uses the following criteria to determine the appropriate BTU levels.


Temperature considerations matter, including your ideal home temperature, the local climate, the quality of your home’s insulation, and how much heat your appliances produce.

Physical Characteristics

Physical considerations such as the floor plan, square footage, and number of people living in the house are also important factors that affect a heat pump’s capacity to function optimally.

These things can help an HVAC professional know which BTU rating will work best for your home. If you’re looking to install a new heat pump, an HVAC contractor can give you estimates on installation and maintenance.


Whether you’re looking to install, replace, or maintain a residential or commercial heat pump system or a more traditional HVAC system, Scott-Lee Heating Company in the greater St. Louis area can help. Our technicians are willing to come out and take measurements in your home or business to determine the proper BTU rating your system needs. Contact Scott-Lee Heating Company today for more information!