Understanding Your Heat Pump System

A heat pump is an all-in-one HVAC system, designed to move heat around rather than generate it on its own. Indoor and outdoor units work together to control the heat, either pulling it in or blowing it out to adjust indoor temperatures. This makes heat pumps an extremely energy efficient HVAC option, but only if they are sized correctly.

Electric heat pump coil illustration

Undersized or Oversized Heat Pumps

Does it really matter if your heat pump isn’t quite the right size? Yes, it really does. That is unless you enjoy paying higher utility costs and extra repair fees. If a unit is too small, it will struggle to produce enough energy to heat and cool your home. To compensate, it will work harder to meet temperature demands, wasting energy and money or breaking down altogether. In contrast, if the unit is too large, it will produce excess energy, which will also waste resources. Other problems that may occur as a result are:

  • Increased on-and-off cycling (resulting in increased stress on the motor blower)
  • Uncomfortable, drastic temperature differences
  • Ineffective control of indoor humidity
  • Short-cycling

How do I Size a Heat Pump?

To size a heat pump for any home, the HVAC industry follows a standard sizing method known as Manual J, established by the Air Conditioning Contractors of America. This procedure goes room-by-room to help determine how much conditioned air each room needs, for both heating and cooling. It looks at eight different factors to establish the appropriate heat pump size for your home.

The eight factors considered in Manual J:

1. The local climate and how many days a year you need active heating and cooling

Your local climate determines how hard your heat pump needs to work during specific seasons. For instance, Florida residents use their HVAC systems much more in the summer months than the winter.

2. The home’s layout, such as square footage and shape

You can determine your square footage in two ways. First, check whether you have your home’s blueprints, as it should tell the exact square footage for each room. If you don’t have access to this information, you can find the area of each room and add it all together to find the total square footage, omitting rooms that do not need heating and cooling, such as a garage. The size and layout help determine how much power your heat pump will need to heat and cool your home.

3. The number and location of windows

The location of your windows can greatly affect HVAC efficiency due to the amount of heat they let in. The most efficient placement allows your windows to let in solar heat in cooler months and minimize it in warmer months. Due to the sun’s positioning throughout the day, southern facing windows allow more heat into the home, while northern facing window let in the least amount. If your property has large, south-facing windows, your heat pump may need to use more energy when cooling. Properly placed windows will cut your HVAC system some slack, and reduce the amount of energy needed to heat and cool your home.

4. How much air infiltration occurs

Air infiltration is one of the most challenging factors to determine, as it is usually more of an estimate. Is your house noticeably cooler on a windy day rather than a calm day? Are there drafts present in specific areas of your home? If your home lets in a significant amount of air flow from outside, you may need a larger HVAC system.

5. How much insulation the home has- whether it meets the region’s efficiency rating

Insulation is your home’s defense against outdoor temperatures in both the winter and the summer. A home with more insulation allows greater resistance to outside elements and creates less strain on your HVAC system. Homes over 30 years old can usually benefit from additional insulation to lower their HVAC’s energy usage. This is one of the most cost-effective ways to increase your HVAC system’s efficiency and lower your energy bills. In a properly insulated house, you can choose a smaller heat pump, as it will not need to use as much energy to keep your home comfortable.

6. How many people live in the home

The number of people residing in your home impacts your cooling needs and how many rooms need to be heated or cooled at once. The more people in the home, the warmer it gets. Commonly used spaces generate the most amount of heat. In turn, they require more air flow to keep them cooler. This can have a significant impact on the size of the cooling system for homes that have multiple residents.

7. How residents use the home and their temperature preferences

Your personal comfort levels are the determining factor when choosing the right HVAC system. While some people may feel comfortable at a lower temperature, others are more comfortable in a warmer environment. Knowing your ideal comfort level helps to determine the right size heat pump for you needs.

8. Other appliances in the home that generate heat

Your home’s appliances can also affect your HVAC sizing needs as they can make rooms warmer. Commercial style kitchens, standalone freezers, and home offices with multiple printers, computers, or monitors can all have a significant impact on the temperatures throughout your home.

The Rule of Thumb for a Heat Pump Properly Sized for Your Home

While all these factors are used by contractors to determine the exact size heat pump you need, there is a general rule of thumb you can follow. For every 500-600 square feet of conditioned floor area, install one ton of air conditioning capacity. And since most sizes of heat pumps are determined by BTU (British Thermal Unit), you'll also need to know that each ton is worth 12.000 BTU.

A Manual J calculation may be a little complex for homeowners who aren't heating or cooling professionals, so our team of experts will help to determine what size heat pump is right for your home. Reach out today to have a team member determine the right sized heat pump for you.

Other Factors to Consider

Once you know what size heat pump you need, there are a few other factors to consider as you invest in a new heat pump. You obviously want a good price, but higher upfront costs may be worth it to save you from paying higher monthly operating costs during the life of your unit. Here's what to look for:

  • Energy Efficiency Ratings: SEER and HSPF. The higher the rating, the more efficient the unit.
  • Blower Motor Type: Fixed Speed, Multi-Speed, or Variable Speed. These describe the type of blower motor and will affect how efficiently the heat pump works and its ability to provide comfort.
  • Compressor Type: Single Stage or Two-Stage. The single stage compressor only heats/cools at full blast, while the other has both high and low speeds, making for much more efficient operation, especially at moderate temperature levels.

Greater Philadelphia’s Heating and Cooling Experts

Sizing your heat pump properly is crucial to the comfort and efficiency of your home. To make sure you get the best heat pump for your family's home and avoid the extra costs and hassle that a poorly sized unit can cause, contact our team of experts to do the calculating for you. We'll guide your decision so you can enjoy higher effectiveness, fewer repairs, and a longer lasting system.

Click here for even more home heating systems comparisons.

Learn more about the different home heating systems and which one is best for your home.

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Our team of experts can help you find the best heat pump for your home so you can live in total comfort. Click below to schedule an appointment online or give us a call at (610) 825-4400.

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