SEER2 What Is SEER2: Step-by-Step Checklist for Choosing Efficient AC

What is SEER2 and why did it replace SEER?

SEER2 (Seasonal Energy Efficiency Ratio 2) measures how efficiently an AC or heat pump cools over a typical season. The big upgrade vs. old SEER is the test conditions. SEER2 uses higher external static pressure (0.5" w.c. instead of 0.1"), which better reflects real ductwork in real homes. Because the test is tougher, the numbers come out a bit lower than SEER but they’re more honest. Think of SEER2 as a “real-world” mpg rating.

use SEER2 when comparing new equipment and plan your system as a package outdoor unit, air handler or coil (air handlers) so everything is matched for the performance you’re paying for.

SEER vs. SEER2: how to compare without getting lost

As a quick mental conversion, SEER2 is typically about 4–5% lower than the old SEER for the same hardware. If you see legacy SEER data in a brochure, a 14 SEER ≈ 13.4 SEER2. But don’t shop on conversion charts alone. Two “equal” SEER2 units can behave very differently in your house depending on duct static, coil match, and setup. Ask for the AHRI matched system number on your quote and verify the SEER2/EER2 values for that exact pairing. If your ducts are restrictive, a great variable-speed system can still underperform so part of “buying efficiency” is fixing the air side during the install.

What SEER2 rating do I actually need?

Use climate, usage, and budget. Rough guide:

• 13–14 SEER2: Baseline. Works for small spaces or mild climates.

• 15–18 SEER2: Sweet spot for most homes—solid savings without a steep price jump.

• 19–25+ SEER2: Top tier. Best where cooling loads and electric rates are high.

If you’re considering ductless mini-splits, many offer excellent SEER2 and zoned comfort (ductless systems).When in doubt, aim for 15–18 SEER2 and invest the rest of your budget in proper sizing and installation quality.

Step 1 Assess your home’s cooling load (the right way)

Start with square footage of the cooled area. A quick sanity check is ~12 BTU per sq. ft. (e.g., 1,800 sq. ft. × 12 = 21,600 BTU ≈ 1.8 tons). That’s only a rough screen. Real load depends on insulation, window area and orientation, ceiling height, air leakage, people count, appliances, and local weather. Add-ons like sunrooms or bonus rooms can swing the total. Write down these factors before you call pros good contractors will ask. Want a head start? See our Sizing Guide, then request a Manual J with your quotes so you’re not guessing by tonnage alone.

Step 2 Pick the right system type for your home

• Central split AC/heat pump: Whole-home comfort if you have decent ducts. Pair with a matched air handler or furnace + coil for best results (AC & gas furnaces).

• Ductless mini-split: Perfect when ducts are missing or leaky, or for add-ons and offices. Flexible single- or multi-zone setups (ductless mini-splits).

• Packaged units: All-in-one rooftop or pad-mount. Great for tight indoor spaces or replacements (residential packaged AC).

• Room units (window/through-the-wall/PTAC): Target a single space or apartment (window units).

Match the choice to your layout, electrical capacity, and where the outdoor unit can breathe.

Step 3 Focus on efficiency features that actually save

Beyond the SEER2 label, features matter:

• ENERGY STAR®: For central split AC, look for ≥15.2 SEER2 (and solid EER2 for hot afternoons).

• Variable-speed/inverter compressors: Better part-load efficiency, quieter, tighter humidity control.

• Smart controls: Scheduling, geofencing, and data help trim waste.

• Clean refrigerants: R-32 equipment improves capacity per pound and can simplify service (R-32 condensers).

• Air quality options: High-MERV filtration, coil coatings, and dedicated ventilation if needed.

Think long-term: a well-controlled, right-sized 15–18 SEER2 inverter can beat a poorly installed 20+ SEER2 on your actual bill.

Step 4 Get the sizing right (Manual J beats rules of thumb)

Oversized systems short-cycle: rooms cool fast but feel clammy, filters load slowly, and parts wear quicker. Undersized systems run nonstop and still can’t keep up. Ask your contractor for a Manual J load calc (and Manual S/D for equipment/duct selection). They measure supply/return static pressure and check existing ductwork. If ducts are small or leaky, plan fixes during the install not later. Use our Design Center to share details and get better recommendations up front.

Step 5 Plan your budget, rebates, and payback

Installed cost depends on home size, efficiency level, duct changes, electrical upgrades, and local labor/permits. A rough range many homeowners see is several thousand dollars for standard split systems, moving higher for multi-zone ductless or premium inverter packages. Balance upfront vs. operating cost: higher SEER2 units cost more but can cut bills for years especially if your utility rates are high. Check utility rebates and tax incentives and don’t forget financing options. Ask your contractor for a simple payback estimate using your actual kWh rate, cooling hours, and thermostat settings.

Step 6 Compare models and quotes like a pro

Get 3–4 written quotes from licensed, insured contractors. Each should include: the AHRI match number, SEER2/EER2, noise ratings (look for low dB at typical operation), warranty details, and scope (duct fixes, pads, disconnects, line-set work). Don’t shop equipment price alone compare the total system and install plan.

If you need quick help choosing categories or accessories, browse our Help Center for what typically rides along with a replacement.

Step 7 Installation day: details that protect your efficiency

Smart prep pays off. Confirm permits, clear paths for equipment, verify electrical capacity, and have the pad/stands ready. On install day, watch for the basics: nitrogen-purged brazing, proper vacuum to 500 microns or better, weighed-in refrigerant charge, leak check, and airflow set to match the coil/heat-pump mode. Your tech should measure supply/return static, confirm temperature split, and register warranties. If running new lines, use the right line sets and follow manufacturer torque specs. Before they leave, get a quick tutorial on your thermostat and filter access.

Step 8 Dial in the setup after install

Program your thermostat for your schedule (a smart stat helps). Typical starting points: 78°F when home in summer, a few degrees higher when away, and use ceiling fans to feel cooler without cranking the setpoint. For multi-zone or ductless, set realistic temperatures per room instead of “max cool.” If humidity is high, let the system run longer at lower fan speeds for better moisture removal. Consider zoning or wall-mounted ductless heads in hot spots (wall-mounted mini-splits) to take load off the main system.

Step 9 Maintenance that keeps SEER2 performance alive

Monthly, inspect and replace filters as needed (more often with pets or renovation dust). Quarterly, rinse outdoor coils and keep two feet of clearance around the unit. Annually ideally before cooling season schedule professional service: coil cleaning as needed, electrical checks, refrigerant verification, condensate treatment, and a static pressure reading to catch duct issues early. Keep shrubs trimmed, clear the drain line, and make sure supplies/registers aren’t blocked by rugs or furniture. 

For packaged or PTAC gear, follow the manufacturer’s cleaning intervals (PTAC units).

FAQs:

Does SEER2 change anything for my current AC?

No. Existing systems keep their original rating. SEER2 applies to new equipment tested under the updated standard.

How do I convert SEER to SEER2?

A simple rough rule is SEER2 ≈ SEER × 0.955. Use it for ballpark comparisons only; always rely on the AHRI match for the exact system you’re buying.

Is a higher SEER2 always worth it?

Not always. If your ducts are poor or the install is sloppy, you won’t see the savings. Often, a 15–18 SEER2 inverter with great installation beats an ultra-high SEER2 on a bad duct system.

What’s the difference between SEER2, EER2, and HSPF2?

SEER2 = seasonal cooling efficiency. EER2 = efficiency at a single hot-day condition (helpful in very hot climates). HSPF2 = seasonal heating efficiency for heat pumps.

How often should I change filters?

Check monthly; replace as needed. Many homes fall in the 1–3 month range. High-MERV filters load faster—watch pressure and airflow.

Do mini-splits really save more?

They can. Zoned control and inverter operation help avoid duct losses. For additions or rooms that vary in use, they’re hard to beat (mini-splits).

Can I use R-32 equipment in my home?

Yes where available and permitted. R-32 units are efficient and service-friendly when installed to code (R-32 systems).