Homeowner Questions · Costs and decisions
What size heat pump does my house need?
Heat pump size is set by the home's heating and cooling load, not by square footage alone. Insulation, windows, air leakage, ceiling height, duct capacity, orientation and local winter design temperature all matter. A contractor should do a load calculation and check that the ducts and backup heat match the selected system.
Checked October 26, 2026 · Educational guide, not a quote.
Quick answer
Heat pump size is set by the home's heating and cooling load, not by square footage alone. Insulation, windows, air leakage, ceiling height, duct capacity, orientation and local winter design temperature all matter. A contractor should do a load calculation and check that the ducts and backup heat match the selected system.
The short version
- Square footage alone does not size a heat pump.
- Ask for a load calculation and duct check.
- Cold-climate output at low temperature matters.
- Tonnage also determines the Ontario per-ton rebate.
Why bigger is not always better
An oversized system can cost more, cycle poorly in cooling season and still fail to fix weak ducts. An undersized cold-climate system may lean on expensive backup heat too often. Variable-capacity equipment gives more flexibility, but it does not erase design mistakes.
What a proper sizing visit includes
The contractor should review the home's size and layout, insulation clues, windows, existing equipment, duct sizes, return air, electrical panel and the temperatures the home must handle. Past fuel use can also help validate the calculation.
How size affects the rebate
Ontario's rebate is paid per ton, so a 3-ton eligible system receives more than a 2-ton system at the same fuel rate. Never choose an oversized unit just to chase rebate dollars; comfort and operating cost come first.
What to do next
Bring past fuel or hydro bills if available.
Ask how the contractor calculated the load.
Confirm backup heat and duct capacity before signing.
Read the full guide
This answer connects to Heat Pump Cost in Ontario, where the full topic is covered with the current Ontario figures and the next checker.
Get the size and rebate checked together
Tonnage sets both comfort and the Ontario rebate. A proper visit should explain the load calculation, not just copy the old furnace label.
Check your rebateQuestions people also ask
What size heat pump does my house need?
Heat pump size is set by the home's heating and cooling load, not by square footage alone. Insulation, windows, air leakage, ceiling height, duct capacity, orientation and local winter design temperature all matter. A contractor should do a load calculation and check that the ducts and backup heat match the selected system.
Can I copy the size of my old air conditioner?
Not safely. The old AC was sized for cooling, may itself be wrong, and does not tell you the home's full winter heating load.
Does a 3-ton heat pump always produce 3 tons in deep cold?
No. Capacity falls as outdoor temperature drops. Check the manufacturer's low-temperature output and the backup-heat design.