Why Size Matters When Choosing a Heat Pump

hvac units

Heat pumps have become one of the best options for homes and small businesses. But size definitely matters when choosing which heat pump to install.

Today’s homeowners have numerous heating and cooling systems at their disposal. From gas furnaces and boilers; to radiant heating and pellet stoves, the possibilities continue to grow. Each system boasts an array of benefits when compared to other options. As many homeowners have found out, though, not all of them are created equally.

For quite a few people, heat pumps are the best choice. These systems offer an array of advantages. They provide heating, cooling, dehumidification, and air filtration. At the same time, they’re considered among the most efficient HVAC systems on the market. Of course, their actual efficiency and effectiveness are dependent on choosing the right size unit for the home in question. 

Why Does Size Matter When Selecting a Heat Pump?

Many people may question why size matters when selecting a heat pump. Some believe that choosing a larger unit is sure to generate more powerful heating and cooling. Others feel that a smaller unit may cost less to purchase and operate than a larger one. In truth, neither of those assumptions is entirely accurate. 

When choosing an appropriate heat pump for a home, several factors should be considered. It’s best to work with a qualified HVAC contractor to find the perfect heating and cooling system for a home. In the meantime, take a look at why having the right system in place is crucial.

Upfront Investment 

Purchasing the right size HVAC unit is important in terms of initial investment costs. Obviously, larger, more powerful systems cost more than smaller ones. Those who think that larger systems will automatically heat and cool their homes better often spend more than they need to when purchasing a system. In the long run, they don’t actually experience more effective climate control. 

On the other hand, homeowners may choose smaller systems than they need in an attempt to save money upfront. With a system that’s too small, though, they find themselves spending more over the long term. Those added expenses come from numerous sources, which we’ll discuss in further detail as we proceed. 

Operating Costs

As noted, a system that’s too large for a space won’t actually cool or heat more effectively than an appropriately sized one. Furthermore, it’ll cost more money to operate over time. Larger systems require more energy to start up than smaller ones, so if they’re too large for a home, even turning them on will cost more than necessary. 

From there, units that are too powerful for a space tend to short cycle. That means they start up, run for a short time, and quickly shut off. Along the way, they don’t really provide the heating, cooling, air circulation, and humidity control they should. They essentially burn energy without doing their job. 

From the opposite perspective, a unit that’s too small for a home can be equally expensive to operate. Instead of short cycling, it may run all the time without heating or cooling a space effectively. That means it’s constantly using energy to no avail. 

Maintenance and Repair Costs

Improperly sized heat pumps are bound to require more maintenance and repairs as well. With those that are too large, constantly cycling on and off takes a major toll on their components. Those that are too small and run continuously are sure to wear out quickly as well. Because of that, simply keeping the system up and running will drive up the cost of ownership.

In either case, a unit that’s the wrong size for a house will need to be replaced sooner than one that’s right for the space it’s serving. Heat pumps generally last an average of 10 to 15 years. If they’re working harder than they should, though, they may not last that long. That’s true even with ongoing maintenance. As such, the cost of more frequent replacements will factor into the equation. 

Additional Problems

Certain additional issues could enter the mix with an improperly sized heat pump. These are long-term problems many homeowners overlook. As mentioned, systems that aren’t the right size for a home won’t provide the temperature and humidity control and other services expected of them. That, in turn, can cause a range of household eventualities.

For one, a system that doesn’t control humidity very well can bring about low indoor moisture levels. That may cause wood flooring and furniture to shrink and crack. It’s sure to affect walls, ceilings, and window and door frames as well. On top of that, it can have a negative impact on appliances and electronics. 

High indoor humidity levels can be equally detrimental. Too much moisture in a home can cause wood and other structural components to swell and warp. It also creates prime conditions for mold and mildew growth, which may bring about an entirely different set of problems. 

Uncontrolled humidity levels combined with an HVAC system that isn’t working properly are also likely to detract from indoor air quality. Since we spend most of our time indoors these days, indoor air quality is a major factor. It can lead to serious health issues and may have significant long-term implications.

How to Find the Right Size Heat Pump for a Home

With all that in mind, it’s easy to see why finding the right size heat pump is important for homeowners. Of course, like so many things in life, that’s easier said than done. Fortunately, a set of guidelines have been established to make matters simpler. They’ve been compiled into a book known as Manual J, and they’re the standards by which the HVAC industry is expected to operate. 

Per the guidelines contained in Manual J, eight specific factors should be taken into account when determining which size heat pump is best for a home. HVAC capabilities are sized according to BTUs or British thermal units. A BTU is a measure of how much energy is required to add or remove heat in an hour. 

In general, experts recommend 30 BTUs for each square foot of space in a home. Another way to look at the algorithm is to calculate one ton, or 12,000 BTUs, for every 500 square feet of space to be heated or cooled. With that being said, we can look at the individual factors used to determine more accurately how much heating and cooling power a home needs. 

Size and Layout of the Home

As many homeowners might imagine, the size and floor plan of a home are crucial aspects to look at when choosing the right heat pump. After all, the size of the home determines just how much space will need to be heated or cooled. 

The complexity of its layout will affect how a heat pump performs as well. A home that has more walls, turns, stairs, and other structural elements to contend with may need a larger unit than a single-story house with a straightforward design, even if they have the same square footage.

Number of Windows in the Home

Windows can affect the size of the heating and cooling system required as well. Research indicates that windows are among the main areas of heat transfer in most homes. That’s especially true in homes with older, more inefficient windows. As such, homes with numerous older windows may need more powerful heat pumps. Those with newer, more efficient windows that are in optimal condition may need less heating and cooling capacity.

Other Sources of Heat Transfer

Windows may be among the most notorious culprits for heat transfer, but they don’t act alone. A great deal of energy is often lost through doors. If doors don’t fit into their frames well or their weather stripping is worn, they’ll have gaps around them. That allows air from outside to come inside while letting heating and air conditioning escape. 

Attics can allow heat or cold air from outside to work its way inside as well. Studies show that at least 40 percent of homes’ heat transfer can occur through the attic. All those elements can affect a home’s energy efficiency. That leads to higher or lower heating and cooling requirements. 


Insulation is likewise a major factor to keep in mind. If a home is insulated well, heat transfer won’t be as much of a problem. If it doesn’t have enough insulation, it will be more of an issue. Different areas have different insulation requirements and recommendations based on the local climate. 

It’s best to ensure a house meets local insulation requirements before choosing a new heat pump. That’ll boost the home’s energy efficiency. By extension, it’ll guarantee that the new heating and cooling system will work better from the beginning. While this requires an added investment, it’ll actually lower heating and cooling costs in the long run.

Several types of insulation are available. Standard fiberglass is the most common, but many authorities on the subject insist it’s one of the least effective options. Still, it comes in numerous forms and can offer adequate R-value. Cellulose is said to be a bit more efficient though ensuring it’s installed properly is crucial. It’s also prone to settling, so it may need to be reinforced after installation.

Spray foam insulation is rapidly gaining ground. This type of insulation is applied via a sprayer and expands to fill cracks and crannies. It’s one of the most effective choices, but it can be more expensive upfront than its counterparts. In areas that are hot and sunny most of the year, having a radiant barrier in place in the attic will help reduce heating and cooling costs as well.

Number of People in the Household

To the surprise of many homeowners, the number of people in the household can impact the size of the heat pump needed. Most people have probably noticed that their home seems to be hotter and more humid during parties or family gatherings. People generate heat, and their activities can do the same. That means the more people living in the home, the more heating and cooling capacity they’ll need to maintain comfortable indoor temperatures and humidity levels.

Number of Appliances in the Home

Appliances can affect the heating and cooling needs of a household, too. Most appliances and devices generate at least some level of heat. Stoves certainly fall into this category, as do dryers. Dishwashers, washing machines, refrigerators, and other items create heat and humidity as well. Even televisions and computers can ramp up the amount of heat in a home. 

Keep in mind the number of people in a home will also influence just how much heat those appliances generate. A household with five people will likely do more laundry than one with only a couple of people. They’ll take more showers as well, which can also create excess heat and humidity. They may cook and wash dishes more often, too. Appliances and household size go hand in hand to help determine the right size heat pump for a home. 

Local Climate and Weather Patterns

Local climate and typical weather also enter the mix. Despite energy efficiency, insulation, and other measures, heating needs are higher in areas with prolonged freezing temperatures, excessive snowfall, and ice accumulation. For homes in hotter, more humid areas, air conditioning is the main focus. In more temperate climates, homeowners may need smaller heat pumps than those who live in locales with more extreme temperatures.

Personal Preferences

Personal preferences also factor into the situation. Some people want their homes to remain a bit warmer or chillier than the norm. They may need a somewhat larger heat pump to meet those expectations than those whose preferences fall into the average range.

Finding the Perfect Heat Pump for a Home

Heat pumps can offer numerous advantages over other heating and cooling options. They operate more efficiently than certain other HVAC systems, and they can be more environmentally friendly. They may require less maintenance as well. Some even last longer than other types of systems. 

Whether a homeowner can truly enjoy those benefits depends on having the right size heat pump installed, though. If a unit is too large or small for a home, it’ll cost more to operate and maintain. It won’t work as well, either. 

When finding the right size heat pump for a home, the size of the home and household, the energy efficiency of the house, the appliances being used, and the typical local climate should all be taken into account. Homeowners’ preferences matter, too. All that can make for a complicated decision-making process. Working with knowledgeable and experienced local HVAC contractors takes the guesswork out of the equation.