How do I size an air conditioner in Canada?

Calculate your home's design cooling load using a room-by-room load calculation, then select an AC with a sensible capacity between 95% and 115% of that load per standard equipment sizing practice. Oversizing an AC is a common mistake — an oversized unit short-cycles and fails to dehumidify properly, leaving the house feeling clammy even at the right temperature.

What SEER2 rating is required in Canada?

Canada's minimum efficiency standard for new central AC is 13.4 SEER2 (equivalent to approximately 14 SEER under the old rating system). Energy Star Canada requires 15.2 SEER2 or higher. Most new Canadian installations now use 16-20 SEER2 equipment. The higher the SEER2, the lower the annual electricity cost.

Is 1.5 tons enough for a 1500 sq ft house?

Maybe — but you can't know without calculating the actual cooling load. A 1,500 ft² house in Vancouver with good insulation might need 1.5 tons. The same house in Toronto facing west with older windows could need 2.5 tons. Square footage rules of thumb are notoriously unreliable for AC sizing. Use the cooling load calculator to get the real number.

❄ Air Conditioner Sizing

AC Sizing Calculator

Size a central air conditioner from your home's cooling load. Applies standard equipment sizing rules (95-115%), converts to standard tonnage sizes, compares SEER2 efficiency levels, and estimates annual electricity costs.

Unit System:

❄ Cooling Load & Conditions

Design Cooling Load * i

BTU/hr

Calculate cooling load →

Annual CDD i

°F·days

Lookup CDD →

Cooling Design ΔT i

°F

⚙ Equipment Selection

SEER2 Rating *

Electricity Rate

$/kWh

Space SHR i

Calculate SHR →

❄ AC Sizing Results

Standard Tonnage Options

SEER2 Efficiency Comparison

SEER2	Annual kWh	Annual Cost	vs 13.4 SEER2

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How to size a central air conditioner correctly

The most common AC sizing mistake in Canada is oversizing. A contractor installs a 3-ton unit in a house that needs 2 tons because "bigger is better" or to avoid a callback. The result: the AC cools the air so fast it shuts off before removing enough moisture. The house hits temperature setpoint but stays at 65% RH instead of 50%. Occupants feel uncomfortable, fiddle with the thermostat, and call back anyway.

The 95-115% sizing rule

Standard equipment sizing practice limits AC selection to 95-115% of the calculated cooling load at design conditions. Below 95%, the system struggles on the hottest days. Above 115%, you get short-cycling and humidity problems. This calculator flags both conditions. The cooling load calculator gives you the accurate load to feed in here.

SEER2 vs. SEER: what changed

SEER2 replaced SEER in 2023. The test procedure uses a higher external static pressure (0.5 in. w.g. vs. 0.1 in. w.g.) that better reflects real-world duct systems. A 16 SEER unit is roughly equivalent to 15.2 SEER2. Canada's minimum is 13.4 SEER2. Energy Star Canada requires 15.2 SEER2. For a Canadian home running AC 500-800 hours per year, stepping from 13.4 to 18 SEER2 typically saves $80-150/year.

Don't forget latent capacity

If your space SHR is below 0.70, standard AC equipment may not remove enough moisture even when correctly sized by BTU/hr. Check the SHR calculator to confirm equipment SHR matches your space SHR.

Frequently Asked Questions

You can't size an AC from square footage alone. A 2,000 ft² home in Vancouver with modern insulation might need 1.5 tons. The same house in Windsor, Ontario with large west-facing windows could need 3 tons. Climate, insulation, window area, orientation, internal gains, and ceiling height all matter. Use the cooling load calculator to get the real number. Contractors who size by square footage are guessing.

At a 24,000 BTU/hr (2-ton) load in Toronto (600 CDD), 16 SEER2 uses about 880 kWh/year vs. 1,060 kWh/year at 13.4 SEER2 — a saving of about 180 kWh or roughly $23/year at $0.13/kWh. That's modest. The payback on a $400 premium for the higher efficiency unit is 17 years — not compelling. The real reason to go higher efficiency is dehumidification: higher SEER2 units often run longer at lower capacity, removing more moisture. In a humid climate like southern Ontario, that's worth more than the electricity savings.

For most Canadian homes, yes. A two-stage or variable-speed system runs at lower capacity most of the time, which means longer run times, better dehumidification, quieter operation, and more even temperatures. The premium is $500-1,200 over single-stage. In humid climates like southern Ontario, the dehumidification improvement alone justifies the cost. In drier climates like Calgary, the benefit is primarily comfort and noise reduction.