SEER2 — Seasonal Energy Efficiency Ratio 2 — is the cooling-efficiency rating that replaced SEER on equipment sold from January 2023. It measures the same thing, seasonal cooling delivered divided by seasonal electricity consumed, but the test now runs against a realistic duct restriction, so identical hardware rates roughly 4–5% lower than it did under the old standard. For most Ontario homes the practical band to shop is 15 to 17 SEER2, and ENERGY STAR certification for split central air sits at a minimum of 15.2 SEER2 paired with 12.0 EER2.
What changed between SEER and SEER2
- The test runs at 0.5 in. w.c. external static pressure instead of 0.1 — a real duct system rather than a bare unit on a test stand
- Identical hardware rates about 4–5% lower: a unit that was 16 SEER is roughly 15.2 SEER2
- Every split system sold in Canada since January 2023 carries SEER2 and EER2 figures on the label
- Heating ratings moved at the same time — HSPF became HSPF2, so don't compare an old brochure to a new one
- SEER2 is a seasonal average across a range of conditions; EER2 is efficiency at one hot design condition, which is why ENERGY STAR names both
What minimum applies in Ontario
Ontario doesn't set its own air conditioner efficiency floor. The minimum is federal, updated when SEER2 came in for 2023, and every split system legally sold in Canada already meets it — which means the base model in your quote is at the floor by definition rather than by choice. Where the number matters is above that floor: ENERGY STAR certification for split central air conditioners requires at least 15.2 SEER2 with 12.0 EER2, and several rebate and utility programs use ENERGY STAR listing as the eligibility test rather than writing their own threshold.
The rating only applies to the matched system
This is the part that costs homeowners money. A SEER2 number is certified for one specific outdoor unit paired with one specific indoor coil, and often a specific blower. Bolt a 17 SEER2 condenser onto the 15-year-old coil already sitting on your furnace and the brochure number no longer describes anything you own — the AHRI directory entry for that actual combination does, and it will be lower.
Ask for the AHRI reference number for the combination being quoted, in writing, alongside the model numbers of the condenser, the coil and the blower. A contractor who installs matched systems produces it without blinking. It also matters for warranty: several manufacturers reduce or void parts coverage on a deliberately mismatched pairing.
Your ductwork decides whether you ever see the rating either. Because the SEER2 test assumes a duct system at 0.5 in. w.c., a house that runs meaningfully higher static pressure hands back part of what you paid for. Plenty of 1970s and 80s subdivision houses across Mississauga, Burlington and Oakville were ducted with a single central return and trunk lines sized for heating alone, then had cooling added later. A static pressure reading during the quote takes a technician five minutes and tells you whether a high-efficiency variable-speed unit can actually breathe in your basement.
What rating should you buy?
- Base single-stage at the federal minimum — the cheapest option, sensible for a rental, a property you're selling soon, or a house where the AC runs a handful of days a year
- 15–16 SEER2, frequently two-stage — the practical GTA choice, and where ENERGY STAR eligibility begins
- 17–18 SEER2 — longer, gentler cycles that pull more humidity out of the air, and a noticeably quieter outdoor unit
- 19 SEER2 and up, inverter-driven variable capacity — the best comfort and dehumidification, typically a $500–$1,500 premium over an equivalent base-brand unit, and worth it if the condenser sits under a bedroom window or the house runs damp
Free quotes, written pricing.
What a higher rating actually saves in our climate
The arithmetic is a ratio, not a promise. Replacing a 13 SEER unit from the mid-2000s with a 16 SEER2 machine cuts the electricity used for the same cooling by roughly a fifth. Stepping from there to 22 SEER2 cuts a quarter off a number that is already much smaller. Ontario's cooling season runs from roughly late June to early September, so the first step pays back in a reasonable span and the second one usually does not.
The honest order of spending is sizing first, staging second, headline efficiency third. An oversized single-stage unit short-cycles, never runs long enough to dehumidify, and leaves the house clammy at 22 °C no matter what the label says — our AC sizing guide explains how the load calculation works.
Heat pumps: SEER2 for cooling, HSPF2 for heating
A heat pump carries both ratings, and in Ontario the heating side matters more because heating hours dwarf cooling hours. HSPF2 is a seasonal average, though, and it doesn't tell you what the machine does on the coldest night. For that, read the manufacturer's rated heating capacity at -15 °C and at -25 °C, which is the specification cold-climate programs and technicians actually work from. See cold-climate heat pumps in Toronto.
Does SEER2 change your rebates?
Standalone air conditioner rebates in Ontario are thin. The Home Renovation Savings Program, run through Enbridge Gas and Save on Energy since January 2025, is pointed at heat pumps and building envelope work rather than at cooling-only equipment. Where SEER2 does matter is eligibility: programs that reference ENERGY STAR are effectively referencing that 15.2 SEER2 / 12.0 EER2 threshold. Check the current Ontario rebate picture before you assume a model qualifies.
Two house-specific tie-breakers are worth naming. If a household runs humid — damp basement, allergy concerns — go inverter-driven, because long low-output cycles pull moisture out and short blasts don't. And if the ducts are original to a house with a single central return, fix the return before buying the efficiency, or you'll pay for a rating you never receive.
Get help choosing
ZK Mechanical sizes and specifies air conditioners across Burlington, Oakville, Hamilton and the wider GTA, and we quote the AHRI-matched combination rather than a condenser model on its own. If you're budgeting the project, our GTA AC installation cost guide shows where the efficiency premium sits against everything else. See our cooling services or request a free assessment.
Frequently asked questions
What is the minimum SEER2 rating in Ontario?
Ontario sets no provincial minimum. The floor is federal, updated when SEER2 took effect in 2023, and every split system legally sold in Canada meets it — so the base unit in any quote is already at the minimum. The useful threshold above it is ENERGY STAR, which for split central air requires at least 15.2 SEER2 together with 12.0 EER2.
Is higher SEER2 always better?
Better, yes; worth it, not always. Replacing a mid-2000s 13 SEER unit with a 16 SEER2 machine cuts cooling electricity by roughly a fifth. Stepping from 16 to 22 SEER2 trims a quarter off a much smaller remainder, across a cooling season that runs from late June to early September here. Spend on correct sizing and staging before you spend on the last few points.
What's the difference between SEER and SEER2?
SEER2 was introduced January 2023 with more rigorous testing — specifically higher external static pressure (0.5 inWC vs. 0.1 inWC) that better reflects real-world ductwork. As a result, the same physical equipment rates ~5% lower on SEER2 vs. old SEER. A 16 SEER unit by old measurement is roughly 15.2 SEER2. The equipment didn't get worse — the rating got more honest.
Do I need an ENERGY STAR air conditioner?
Not by law, but it is a useful shorthand. ENERGY STAR for split central air means at least 15.2 SEER2 and 12.0 EER2, comfortably above the federal floor, and several rebate programs use the ENERGY STAR listing as their eligibility test instead of writing thresholds of their own. Confirm the listing applies to the matched indoor and outdoor combination, not just the condenser.
How does SEER2 apply to heat pumps?
A heat pump carries SEER2 for cooling and HSPF2 for heating, and in Ontario the heating figure carries more weight because heating hours far outnumber cooling hours. HSPF2 is still a seasonal average, so it says little about the coldest nights. For that, read the rated heating capacity at -15 °C and -25 °C, which is what cold-climate programs and technicians actually work from.