Heat Pump Sizing: The Ultimate Guide on How to Choose Heat Pump Size

A correctly sized heat pump can make all the difference when it comes to keeping your home comfortable, energy-efficient, and cost-effective. Heat pump sizing is critical to ensuring optimal performance and comfort in your living space.

In this heat pump sizing guide, we will explain how to choose your heat pump size, why size matters, what impacts a sizing, how to find the right contractor and more. We will walk you through everything you need to know about heat pump size.

We’ll cover:

• What are the benefits of heat pumps?
• Why does heat pump size matter?
• Is it better to oversize or undersize a heat pump?
• What happens when the heat pump size is wrong?
• What factors impact heat pump sizing the most
• How can you accurately size a heat pump for your home?
• How do heat pumps work?
• What are the costs of installing a heat pump in Canada?
• Are rebates available for installing a heat pump in Canada?

What Are The Benefits Of Heat Pumps?

Heat pumps have a few benefits, including that they can both heat your home in winter and cool your home in summer. They are versatile pieces of equipment that can be installed in different sizes and configurations to meet the needs of almost any dwelling.

They are much more energy-efficient than other means of heating, and do not burn fuels to create greenhouse gasses.

Why Size Matters For Heat Pumps

Getting the right size for your heat pump is crucial because an improperly sized unit can lead to performance issues, discomfort, increased energy bills, and even potential damage to the system.

An undersized heat pump will struggle to meet the heating and cooling demands of your space, while an oversized one may short cycle, turning on and off frequently, leading to inefficiency and wear and tear.

What Happens If The Size Is Wrong?

When it comes to heat pump sizing, “just right” is the goal. Both oversizing and undersizing can result in problems that affect your comfort and budget. Let’s dive into the dangers of each:

The danger of oversizing a Heat Pump

An oversized heat pump might seem like a good idea for quick heating or cooling, but it can create issues. An oversized heat pump is likely to turn on and off rapidly in cooling mode, a phenomenon called short cycling. This not only wastes energy but also places unnecessary stress on the components, potentially shortening the lifespan of the unit.

One of the important functions of a heat pump in cooling mode is to take excess humidity out of the air. Oversized systems might fail to effectively dehumidify your space, leading to a damp and uncomfortable environment. It’s really important to keep your indoor humidity around 50% to minimize the growth of molds (which thrive in high humidity) and bacteria (which like low humidity).

You would be spending more than necessary to purchase the equipment in the first place. Then you would have to replace it prematurely, as constant starting and stopping causes extra wear and tear on the unit.

The danger of undersizing a Heat Pump

On the flip side, an undersized heat pump will struggle to keep up with the heating and cooling demands of your home, especially during extreme weather conditions. This can result in discomfort and frustration as your space won’t reach the desired temperature. Worse, it could cause the outside unit to freeze and stop working.

Most heat pumps include an electric heating element, which kicks in when the heat pump cannot heat the space to the temperature set on the thermostat. Electric heating is much more expensive than heat pump heating, so you could end up paying much more than you expected to heat you home.

Heat Pump Size Calculator

To simplify the process, many online heat pump size calculators are available. These tools take a number of your inputs including square footage, insulation quality, climate, and other variables to provide an estimate of the heat pump size you might need.

While useful, these calculators are not as accurate as a detailed Manual J calculation performed by a professional. Here’s our heat pump sizing calculator which can give you a general idea of the heat pump size and BTU output you will require.

What Impacts Heat Pump Sizing The Most?

Several factors influence the proper sizing of a heat pump. These include:

Size Of The House

Obviously, the more space you have to heat or cool, the bigger the heat pump should be. Ceiling height as well as floor area is important

Climate

The climate of your region plays a significant role in determining the size of the heat pump you need. Colder climates require more heating power, while warmer climates demand efficient cooling capabilities.

Typical heat pump models start losing efficiency when the outside air temperatures fall below around 0°C, and they generally need help from another heating source when the outside air temperature goes much below that. Newer models are available that can cool with outside temperatures down to -25°C, although their efficiency is reduced at lower temperatures.

On the other hand, the typical heat pump does well in air conditioning (cooling) mode in Canada. Even in those areas where the temperatures increase to 40°C, heat pumps that are properly sized should cool adequately.

Insulation

Well-insulated homes retain indoor temperatures better. This affects the heat load on the heat pump. A poorly insulated home will require a larger heat pump to compensate for heat loss or gain.

The most important area for insulation is the attic, either the attic floor (which is the ceiling of the rooms below) or the underside of the roof and associated roof components. This is where the greatest potential heat loss can occur, since your heated air rises. If it encounters a cold surface, its heat will transfer to the colder surface, and you will lose the heat.

The exterior walls are the next most important part of your house to insulate. There’s a lot of area there to be in contact with the cold outdoors and lose your heat. Similarly, they can heat up in summer and transfer heat to your cooler inside air.

Air sealing

How leaky is your house? How much air leaks in and out, taking the energy along that was used to heat or cool it? This can be stopped by an energy efficiency upgrade called air sealing.

Air sealing is a practice that was not used until recently. Newer energy efficiency standards are requiring buildings to be better and better sealed against air leaking in or out through the many places where leakage could occur.

Leakage can occur through gaps anywhere two construction components meet, like walls and floors or ceilings, walls and windows or doors, etc. Also, you can have leaks where pipes, flues, electrical conduits, etc. penetrate walls, floors and ceilings. As you can imagine, there are quite a few places that have to be well-sealed to prevent air rom flowing through the gaps.

Older windows and doors tend to be very leaky. Doors can be weather-stripped better and windows can be caulked around the frames to reduce leakage. But older windows often cannot be adequately weather-stripped.

These leaks on older buildings can add up to a lot of heated inside air exchanging with cold outside air or vice versa. This affects the heat load on the heat pump. A poorly air-sealed home will require a larger heat pump to compensate for heat loss or gain.

It is possible to have a contractor come in to improve the air sealing of your house. They identify the leaks with special equipment and seal them, then measure the results.

Duct efficiency

Ducts are the pathways through which the conditioned air is distributed throughout your house. A substantial fraction of energy can be lost through the duct system if it is leaky or poorly insulated.

Ducts can leak at joints where the duct is attached to the heat pump, where the ducts are attached to the vent openings that distribute the air and between segments of duct. In other word, pretty much everywhere.

Ducts can separate due to continued thermal expansion and contraction as they heat up and cool off, ducts the attic can get separated or damaged by workmen carelessly crawling over them. Critters can make holes in the ducts.

Any of these gaps or holes will leak your conditioned air and waste it; your heat pump size would have to be increased to compensate.

Duct insulation is also very important. If you have cold air going through your duct in a hot attic or wall, or hot air going through your ducts in a cold attic or wall, the ducts will transfer heat from warm to cold and you will lose energy. You would need a larger-sized heat pump than with efficient ducts.

Older ducts usually have less insulation than newer ducts are required to have. In a typical 1980s house, the attic ducts could lose 35% of their energy through this heat transfer. An ideal attic duct installation uses ducts wrapped with insulation that meets the provincial standard, installed on the attic floor, and then covered with blown-in insulation.

Duct configuration can affect the efficiency of the duct system. An original duct system may have been efficient, but if there were additions and changes, the ducts may require more energy to move the required amount of air through them.

Also, since an existing duct system determines how much air blows into each room, this may not be the best arrangement if there have been changes in the building. But the airflow can be adjusted for each room to some extent through the correct selection and use of vents.

Windows and doors

The type and quality of windows and doors in your home impact heat transfer. Energy-efficient windows and doors help retain indoor temperatures, reducing the load on the heat pump.

Older windows can be very leaky. Windows with a single pane of glass lose significant amounts of heat in the winter and transfer a lot of heat inside in the summer. Double-or triple-glazed windows are now standard in new construction throughout Canada, and considerably reduce heat transfer.

Many homeowners replace older windows with newer ones not just for the energy efficiency, but also because they look better. Although this can be a substantial investment, it pays off in increased comfort and lower energy bills.

Similarly with doors, newer doors can be much more energy-efficient than older doors. Doors can be weather-stripped to reduce leakage around them, but older doors may still conduct a lot of heat in or out.

So if you have a number of older windows and doors, you’ll need a larger heat pump size.

Shade and sunlight

The amount of shade and sunlight your home receives affects its internal temperature, room by room. Of course, this impacts the size of the heat pump you need, as well as distribution of the conditioned air.

Rooms that receive direct sunlight need less heating and more cooling; vice-versa for the rooms that are shaded from the sun. Calculations of your heat pump size will take this into account in the design of your system.

The area of windows and doors exposed to sunlight is more important than the area of walls, since they conduct heat more than an insulated wall. So if you have a lot of widows facing north, even if they are newer and better insulated, you may need more heat pump capacity in the winter.

Use of space

The function of different rooms in your home affects the heat load.

Kitchens, for example, tend to generate more heat due to cooking appliances. TVs, computers, printers, and related equipment generate a significant amount of heat.

You might have three of four kids sharing a bedroom; people generate heat and humidity. The number of people in the entire house as well as room-to-room are factors to take into account.

All these factors must be considered in sizing your heat pump.

What Sizes Do Heat Pumps Come In?

Heat pumps come in various sizes to cater to different heating and cooling needs. The size you need depends on factors like the square footage of your home, insulation quality, climate, and more.

These heat pump sizes are typically measured in tons or British Thermal Units (BTUs). Each ton equals 12,000 BTUs per hour.

There are two configurations: ducted, where a single heat pump blows the conditioned air into a duct system for distribution throughout your house; and mini-split, where a single outdoor unit serves up to 5 blower units in individual spaces within your house.

The common sizes of heat pumps range from 1.5 to 5 tons. The units with a capacity of 4 tons and below are available in both ducted and mini-split form.

7,000 BTU and 12,000 BTU sizes are also available as mini-split systems.

Heat pumps of more than 5 tons are not generally available for residential use, but are used in commercial applications. If you have a particularly large residence, you may need more than one heat pump.

How Do Heat Pumps Work?

Heat pumps work by pumping heat from outdoors to indoors or vice versa. In heating mode, an outdoor unit extracts heat from the air or the ground and transfers it indoors where it is distributed. This works in reverse for cooling mode.

Because the process uses electricity to transfer existing heat, it is much more efficient than generating heat by burning fossil fuels or with electric baseboard heating.

How To Size A Heat Pump

Accurately sizing a heat pump involves a combination of methods and considerations. The most accurate method is using a Manual J calculation. This comprehensive calculation takes into account your home’s square footage, insulation quality, climate, windows, and more to determine the ideal heat pump size.

Sizing is governed by CAN-CSA-280-M90, the applicable building code.

Natural Resources Canada recommends that you calculate your cooling load, then size your heat pump to meet 125% of your cooling load. This will not provide for your entire heating load, so you will have to make up the difference with another heating system.

You can calculate the heating and cooling loads separately, but in Canada, the heating load will be more than the cooling load. If you size the heat pump for the heating load, it will be oversized for the cooling load, and cause problems.

Manual J

Manual J is an industry-standard calculation tool that HVAC professionals use to determine a home’s heating and cooling load. It considers factors like insulation, windows, doors, and local climate to provide a precise heat pump size recommendation.

This calculates the heating and cooling design load, what your home requires, which is the basis for heat pump sizing.

Although it is possible to do the calculations manually, computers make it much easier. You could purchase an expensive, complex program, spend more than a few hours learning to use it, and then input all of the information it requires (if you have it). Of course, you’re not going to do that; you’ll leave it to the experts.

As a practical matter, most HVAC installers do not do Manual J calculations on typical HVAC installations. They might do it in designing the HVAC system for new construction of a large residence, or they might charge extra to do it for a typical residence if requested. But it’s a lot of work, and good installers use a short-cut version of Manual J to adjust for all the factors that go into sizing your heat pump.

Square footage

The rules of thumb for estimating heat pump sizes from the square footage of a building have been changing with the changes in construction. The old rule of thumb is that you’ll need about 25-30 BTUs per square foot for cooling and 20 BTUs per square foot for heating. This is usually expressed as 1 ton (12,000 BTU) for every 400 square feet. This might work for an older house with no energy-efficiency upgrades.

A newer rule of thumb, given that building standards require homes to have increased structural energy efficiency, is one ton for every 800 square feet, for newer buildings.

These are rough estimates. These rules of thumb should only be used when you are starting to think about installing a heat pump, to get a general idea of what size you’ll need.

There are so many factors that go into determining heat pump size that you want to rely on either Manual J calculations if you can afford them, or the assessment and judgment of a qualified, experienced HVAC contractor.

More measurements make better estimates – up to a point

The more accurate the data you provide to your HVAC installer, the better they can estimate the appropriate heat pump size. However, keep in mind that excessive measurements won’t necessarily lead to a better outcome.

Also, you probably don’t have accurate information on many of the things about your house that will impact the heat pump size. Do you know the air leakage? The R-value of your older windows and doors? The R-value of your walls and ceilings? An energy audit can help.

Basically, you’ll be trusting the expertise of professionals who can assess your house and correctly size your heat pump.

What Size Heat Pump Do I Need for My Home?

Let’s take a look at a sample heat pump sizing table to give you a better understanding of what size heat pump you might need for different square footages.

These are based on rules of thumb. But there is a big difference in rules of thumb depending on the age of the house. They range from 1 ton for every 400 square feet to 1 ton for every 1,000 square feet, depending on how energy-efficient your home is.

That accounts for the wide range in heat pump sizes for each house size. If your home is older, with no energy efficiency upgrades, use the larger number. If your home is almost new, it is required to be relatively energy efficient, and you can use the smaller size as your rule of thumb. If your home is 10-20 years old, or has energy efficiency upgrades, use a number in between

Detailed Heat Pump Sizing Chart by Square Footage

Here’s a detailed heat pump sizing chart based on square footage, but there’s a large range because newer homes have become increasingly efficient:

• Up to 1000 sq. ft.: 1 to 2 tons
• 1000 to 1500 sq. ft.: 1 to 3.5 tons
• 1500 to 2000 sq. ft.: 1.5 to 4.5 tons
• 2000 to 2500 sq. ft.: 2 to 5.5 tons ª
• 2500 to 3000 sq. ft.: 2.5 to 7 tons ª
• 3000 to 3500 sq. ft.: 3 to 7.5 tons ª
• 3500 to 4000 sq. ft.: 3.5 to 9 tons ª

ª The maximum size for residential heat pumps is 5 tons. If you need more than 5 tons of capacity, you will need more than one unit.

Heat Pump by the Ton

Remember that heat pump sizes are often referred to in tons, with each ton equal to 12,000 BTUs. This measurement helps to simplify the selection process and aligns with industry standards.

Installers are wrong sometimes so get multiple quotes

While HVAC installers are experts in their field, mistakes can happen. Different installers have different experiences and may make different judgments while looking at the same set of factors in your house.

To ensure you’re getting the right size, it’s a good idea to seek multiple quotes from different installers. This can help you identify any discrepancies and make an informed decision.

With the information in this article, you can ask intelligent questions to see how they are taking into account the various conditions that your house has.

It’s A Good Idea To Get An Energy Audit

An energy efficiency evaluation audit, known officially as an EnerGuide evaluation, involves having a qualified energy advisor assess how your home uses energy. It also identifies retrofits to improve its energy efficiency performance.

The report can help you figure out your heat pump size, as well as giving you suggestions for retrofits you can do so that you’ll need a smaller size heat pump.

Bigger Does Not Mean Better

Choosing an oversized heat pump in the hope of getting superior performance is a bad idea. An oversized unit will cycle on and off frequently, reducing efficiency and potentially causing long-term damage to the system.

The only way you can get better performance is by choosing a model that is more efficient at delivering the required number of tons, and by opting for additional features that might help you operate it more efficiently.

Capacity can change with the weather—sometimes

Heat pump sizing is typically based on average temperature conditions. Heat pump efficiency decreases at extreme temperatures, either h

Because heat pumps lose efficiency in these winters, a somewhat larger heat pump may be specified to provide enough heat with low outside temperatures. But if the winters are cold enough, an additional method of heating is usually added to the system, either electric heating or a heating system burning fossil fuels.

It’s OK to leave heat pump sizing to the pros

If you’ve read this far, you can see that sizing a heat pump is a complex task that involves quite a few factors. While it’s valuable to understand the basics, relying on a qualified HVAC professional to perform accurate calculations and apply his experience is the best approach.

Costs of installing a heat pump in Canada

The cost of your heat pump will depend on the type of heat pump, its size, and what is involved with the installation. Split systems, which cover one area, start at about $3,000. Larger systems can run $10,000 to $20,000.

Geothermal systems, where the outdoor heat exchanger is buried at least 4 feet underground or submerged in a body of water, can cost $15,000 to $40,000 or more. But unlike common heat pumps, which get their heat from the outside air, these systems may be able to operate efficiently in extremely cold air, since it is warmer below the surface.

Also, the heat exchanger doesn’t need to be replaced when other parts wear out, so it can be good long-term investment.

Here’s an article that covers how much you’ll pay for a new heat pump installed in Canada.

Find a trusted heat pump installer

Finding a trusted installer is crucial for a successful heat pump installation. Look for recommendations from friends, family, and online sources.

How to spot signs of a quality installer

When choosing an HVAC installer, consider their reputation, certifications, customer reviews, and experience. A quality installer will be willing to explain the sizing process and answer any questions you have.

Check out the company they work for. Are there any complaints about the company online?

Verify their credentials and make sure they are licensed and insured.

Check to see if your unit is eligible for a grant

In some regions, there are grants and incentives available for energy-efficient home improvements, including heat pump installations. Check with local authorities to see if you’re eligible for any financial assistance.

There are substantial rebates available if you are switching from oil heating to a heat pump, up to $10,000. Enbridge Gas customers can get up to $10,000.

The Canada Greener Homes Initiative is designed to help homeowners save money, to create new jobs across Canada, to and fight climate change. It provides grants up to $5,000.

You will need an energy audit to get these grants.

Other tips for getting the best performance from your heat pump.

Optimal heat pump performance goes beyond sizing. Here are a few additional tips:

• Upgrade your home’s energy efficiency (best done BEFORE you get a heat pump): Seal any gaps or leaks in your home to prevent heat loss or gain.
• Energy Efficient Model: Consider investing a little more to get a heat pump of the required size that has a better energy efficiency rating.
• Regular Maintenance: Schedule annual maintenance to keep your heat pump in top shape.
• Thermostat Settings: Set your thermostat to energy-efficient temperatures when you’re away or asleep. Smart thermostats can give you a lot of control over your heat pump.
• Airflow: Ensure proper airflow around the indoor and outdoor units. Clean the outdoor unit twice a year
• Air Filter: Clean or replace air filters regularly to maintain efficiency. Depending on the amount of dust, animal hairs, etc. in your home, you may need to change or clean the air filters every three months.