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. Getting the load number right matters more than the sizing range itself: Canadian heat loss and heat gain calculations are generally based on the methodology set out in CSA F280, the national standard for determining residential heating and cooling equipment capacity. 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, and Energy Star Canada requires 15.2 SEER2 or higher. For a Canadian home running AC 500-800 hours per year, stepping from 13.4 to 18 SEER2 typically saves $80-150/year; the SEER2 calculator breaks that estimate down for your own electricity rate and runtime.
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, and if moisture is still a problem after that, a dehumidifier sized to the excess latent load is usually cheaper than upsizing the AC.
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), a 16 SEER2 system uses about 1,350 kWh per year, compared with about 1,610 kWh per year at Canada's minimum standard of 13.4 SEER2, a saving of roughly 260 kWh or about $34 per year at $0.13/kWh. That's modest. The payback on a $400 premium for the higher-efficiency unit is about 12 years, which is not compelling on electricity savings alone. The real reason to choose higher efficiency is dehumidification: higher SEER2 units often run longer at lower capacity, removing more moisture. In a humid climate like southern Ontario, that benefit can matter 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.