What Should a Heat Pump Sizing Assessment Include?

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Reviewed by Oasis Environments

Updated August 29, 2026

A heat pump should be selected for the actual heating and cooling needs of the building. The size of the old system, the floor area alone and a quick equipment estimate are not enough to design a reliable replacement.

A proper assessment looks at the building, the existing system, airflow and local weather conditions before equipment is recommended.

Why heat pump sizing matters

Heat pump capacity affects comfort, operating cost, equipment life and the amount of backup heat required during cold weather.

An oversized system may turn on and off too frequently, create uneven temperatures and provide weaker moisture control during summer. An undersized system may run continuously, rely heavily on backup heat or struggle during extreme conditions.

The goal is not to choose the largest available unit. The goal is to select equipment that matches the building and the homeowner’s comfort priorities.

Building measurements and layout

The assessment should confirm the size, layout and number of conditioned levels in the home. Ceiling height, additions, open spaces and rooms over garages can all affect heating and cooling needs.

Two homes with the same floor area may require different equipment because their layouts, exposure and construction are different.

Insulation, windows and air leakage

Heat moves through walls, ceilings, windows, doors and areas where outside air leaks into the home.

An assessment should consider:

Attic and wall insulation where information is available
Window type, size and orientation
Exterior door condition
Air leakage and known drafts
Basement or crawlspace conditions
Recent energy upgrades

These details help estimate how quickly the building gains or loses heat.

Local outdoor temperatures

Equipment should be evaluated using Okanagan winter and summer design conditions. A heat pump’s capacity changes as the outdoor temperature changes, so the published heating output at colder temperatures is important.

The assessment should compare the building’s heating requirement with the selected model’s performance at relevant winter temperatures. This also helps determine what type of backup heat is appropriate.

Existing ductwork and airflow

A ducted heat pump depends on the air distribution system. Even well selected equipment can perform poorly if airflow is restricted or uneven.

The assessment should review:

Supply and return duct sizes
Filter size and condition
Visible duct restrictions or damage
Room comfort complaints
Existing blower performance
Airflow requirements for the proposed equipment

Some homes benefit from duct corrections or added return airflow as part of the project. These needs should be discussed before installation rather than discovered after the new system is operating.

Existing heating equipment

The contractor should document the current furnace, air conditioner, heat pump or electric heating system. Equipment age, fuel type, condition and known comfort problems all provide useful context.

The old equipment size can be recorded, but it should not be treated as proof that the same size is correct. Older systems may have been selected using different assumptions or may have been oversized from the beginning.

Electrical capacity

Heat pumps, air handlers and electric backup heat can add electrical demand. The assessment should identify the electrical requirements of the proposed system and whether the existing panel and circuits appear suitable.

A qualified electrician may be required to confirm capacity or complete electrical upgrades. These requirements should be identified early enough to include them in project planning.

Comfort goals and operating preferences

Equipment design is not only a calculation. The contractor should ask how the home is used and what the occupants want to improve.

Useful questions include:

Are certain rooms consistently too hot or too cold?
Is quiet operation a priority?
Does anyone require tighter temperature control?
Is the goal to reduce gas use, improve cooling or replace aging equipment?
Will the existing furnace remain as backup?
Are future renovations planned?

Clear goals help the contractor recommend a system that fits the household instead of presenting a generic replacement.

What should be explained after the assessment?

The proposal should explain:

The recommended equipment and size
How the system will perform during cold weather
The backup heating strategy
Any ductwork or airflow improvements
Electrical requirements
Thermostat and control operation
Installation scope
Parts and labour warranties
Maintenance requirements

Customers should be able to understand why the system was recommended and what is included before approving the project.

Heat pump assessments in the Okanagan

Oasis Environments provides heat pump assessments, installation, repair and maintenance across Kelowna, West Kelowna, Peachland, Penticton and Vernon.

Call or text 250 317 6463 or visit oasisenvironments.ca to arrange an assessment.