SEER2 Glossary: Plain-English HVAC Terms Every Homeowner Should Know

The day SEER2 hit the block (and why your estimate changed)

Last summer, my neighbor waved me down while I was unloading a condenser: “Why does this new estimate say SEER2 instead of SEER?” Great question. In 2023, the industry switched to a tougher, more realistic test. That means today’s labels better match real homes with real ductwork. If you shopped years ago, numbers look a bit lower now that’s normal, not a downgrade. Our plan in this guide: walk through the essential terms (SEER2, EER2, HSPF2, AFUE, tonnage, static pressure, filters, refrigerants), share quick pro tips from actual installs, and help you decide what to do next without fluff. And if you’d like design help, swing by our Design Center we’ll map it out with you..

SEER2 in plain English (the new seasonal yardstick)

SEER2 estimates how efficiently an AC or heat pump cools your home over an entire season. It’s total cooling output (BTUs) divided by electricity used (watt-hours). The updated test cranks up external static pressure from 0.1" to 0.5" water column, which mirrors real duct resistance. Because the test is tougher, SEER2 ratings are often ~0.6–2 points lower than the old SEER for the same equipment but performance didn’t drop; the yardstick changed. Minimums since 2023: 13.4 SEER2 (Northern) and 14.3 SEER2 (Southeast/Southwest). For many homes, stepping up a tier is worth it when summer bills arrive.

EER2: the “hottest day” snapshot

Where SEER2 is a seasonal average, EER2 is a snapshot at 95°F outdoors, 80°F indoors, 50% humidity. If your climate is consistently hot (think desert Southwest or deep South), EER2 can tell you how a unit behaves when the thermometer is grumpy. It’s especially useful for sun-baked rooms, west-facing exposures, and homes with limited shade. When comparing models, a strong EER2 can be your tie-breaker.

When to lean on EER2

1. Peak-load homes: Long, brutal afternoons? EER2 helps.

2. Marginal ductwork: High attic temps can stress systems; EER2 performance matters.

3. Utility rate spikes: If power costs soar during peak hours, better EER2 softens the blow.

If you run the AC hard from 3–7 pm, prioritize EER2 along with SEER2. Ask us to show both on any product short-list.

HSPF2: the heat-pump number that matters in winter

HSPF2 measures how efficiently a heat pump heats across the whole heating season. It uses the same tougher test logic as SEER2, so the number is realistic. Current minimums: 7.5 HSPF2 for split heat pumps and 6.7 HSPF2 for packaged. In milder and shoulder seasons, a good HSPF2 heat pump often beats gas on operating cost; in colder snaps, pairing with backup heat (electric strips or gas furnace) keeps you comfortable and safe.

Smart combos

• All-electric with backup strips for mild climates.

• Dual fuel (heat pump + gas furnace) for variable winters; heat pump runs cheap above a set outdoor temperature, furnace takes over below it. Browse Dual-Fuel & R-32 AC + Gas options.

If your utility offers time-of-use or heat-pump rebates, HSPF2 is your friend. We’ll help decode the fine print.

AFUE: if you’re staying with a furnace

If your home uses a gas or oil furnace, AFUE (Annual Fuel Utilization Efficiency) is your rating. 80–85% AFUE is standard efficiency; 90–98% AFUE is high efficiency (condensing). A 95% AFUE furnace turns 95% of fuel into heat over the season. Upgrading old 70–80% units can make a noticeable dent in winter bills, especially in colder regions. The catch? Condensing furnaces need proper venting and condensate handling; that’s normal, just plan the route.

Quick picks

• Basement? Condensing furnaces often fit well and vent out the side wall.

• Tight closet? Mind clearances and return air—starving the blower reduces lifespan.

• Shopping furnaces? See Furnaces and ask about match-up coils if you’re keeping the existing AC.

If your ducts are leaky, fix them before judging furnace efficiency. The heat you paid for shouldn’t end up in the attic.

The M1 test: why today’s labels feel more honest

The M1 procedure birthed SEER2/EER2/HSPF2. Two big shifts homeowners should know:

• Higher test static pressure (0.5" w.c.) to simulate real-world duct resistance.

• More realistic cycling/airflow conditions, so the lab behaves more like your hallway.

The result? Labels that track closer to how systems actually run. That’s good news for budgets and expectations. If you’re comparing gear from different years, make sure you’re not mixing old SEER with new SEER2. Also, if you’re eyeing ENERGY STAR®, many 2025 qualifying splits target 15.2 SEER2 and 8.1 HSPF2 for heat pumps, and 15.2 SEER2 / 12.0 EER2 for central ACs.

When we design your system, we check external static pressure. If it’s high, we correct duct issues so your new equipment actually earns its label.

Capacity basics: tonnage, BTUs, and airflow you can trust

Tonnage is cooling capacity, not weight. 1 ton = 12,000 BTU/h. Typical homes land here:

• 1.5–2 tons: ~1,000–1,400 sq ft

• 2.5–3 tons: ~1,400–1,800 sq ft

• 3.5–4 tons: ~1,800–2,400 sq ft

Airflow is measured in CFM (cubic feet per minute). A handy rule is ~400 CFM per ton. Undersized returns or crushed flex reduce CFM, raise static pressure, and make even premium gear act average.

How we size (no guessing)

1. Look at windows, insulation, sun exposure, occupants, and ducts.

2. Run a proper load calc

3. Match tonnage + CFM + coil to your conditions.

Use our Sizing Guide to sanity-check numbers.

Bigger isn’t safer. Oversizing causes short cycling, humidity issues, and noise.

8) Cleaner air, clear choices: MERV, MPR, and FPR

Filters come with different yardsticks: MERV (industry-standard 1–16), MPR (3M, 300–2200), and FPR (Home Depot, 4–10). For most homes:

• MERV 6–8: Basic dust/pollen

• MERV 9–12: Good with pets or mild allergies

• MERV 13–16: Serious filtration (think smoke/health concerns)

Higher filtration can raise static pressure if the filter rack is small. We often upsize the filter cabinet or use a deeper media filter to keep airflow healthy.

If you’re jumping to MERV 13, measure pressure drop before/after the upgrade. We can spec a larger cabinet so you breathe easier without choking the blower.

Need help picking a setup? Our Help Center and HVAC Tips blog are good quick reads.

System types that actually fit your home (not your neighbor’s)

Split systems put the coil/furnace or air handler inside and the condenser outside—most common for houses. Package units bundle it all outside; useful where indoor space is tight or for rooftops (see Package Units). Heat pumps can both heat and cool; air conditioners cool only and pair with a furnace or strips. Dual fuel pairs a heat pump with gas for smart switchover in cold snaps.

No ducts or adding an addition? Consider Ductless Mini-Splits quick installs, room-by-room control, and solid efficiency.

For garages, studios, and bonus rooms, ductless avoids long, lossy runs and weird temperature swings.

Ducts, static pressure, plenums, and zoning the hidden heroes

Comfort lives and dies in the ductwork. The supply plenum feeds conditioned air to your home; the return plenum brings it back. Kinks, long flex runs, undersized returns, and stuffed filters raise static pressure (measured in inches of water column). High static makes systems loud, short-lived, and inefficient. If one bedroom is always wrong, consider zoning (thermostats controlling motorized dampers in separate branches).

What we fix a lot

• Undersized returns (we add/upsized them).

• Long flex spaghetti (we straighten/shorten runs).

• No balancing dampers (we add them so rooms stop fighting).

Before buying pricier equipment, spend a little on duct corrections. It’s often the best dollars-per-degree you can invest.

Refrigerants: R-410A vs R-32 what’s changing and why it matters

R-410A has worked well for years but carries a higher global warming potential (GWP ~2,088). R-32 is a newer option with GWP ~675 (about 68% lower) and roughly ~10% efficiency potential in many designs. Regulators and manufacturers are moving that direction, so if you’re shopping today, it’s smart to compare both.

For apartments or hotels, see R-32 PTAC Units.

If you’re replacing the outdoor unit with R-32, plan coil compatibility and line-set details early. We’ll help kit the parts so the installation day goes smoothly.

Your simple, step-by-step shopping plan (bookmark this)

When you’re ready, follow this no-nonsense checklist:

1. Confirm the goal: Cooling only (AC) or year-round (heat pump/dual fuel)?

2. Right size it: Use our Sizing Guide and ask for a load calc.

3. Check the ducts: Measure static pressure; fix returns/long runs now.

4. Pick the rating set: SEER2 + EER2 for hot climates; add HSPF2 for heat pumps.

5. Consider refrigerant: Compare R-410A vs R-32 options.

6. Choose the format: Split Ductless.

7. Plan the parts: Coil match pad, disconnect, filter cabinet.

8. Learn the install day flow: Use our Help Center to speed things up.

9. Budget it: See HVAC Financing.

10. Ask anything: We mean it Contact Us.

Screenshot this list and the model numbers you like. When we talk, we’ll confirm SEER2/EER2/HSPF2, duct readiness, and any ENERGY STAR® or utility rebates that make sense.

Handy glossary recap (pin this)

• SEER2: Seasonal efficiency (newer, tougher test).

• EER2: Peak-day cooling snapshot (95°F).

• HSPF2: Heat-pump heating efficiency across winter.

• AFUE: Furnace seasonal fuel efficiency.

• Tonnage/BTU: System capacity; 1 ton = 12,000 BTU/h.

• CFM: Airflow; ~400 CFM/ton is a good target.

• Static Pressure: Air resistance in ducts; keep it reasonable.

• MERV/MPR/FPR: Filter rating systems.

• R-32 vs R-410A: Lower GWP and efficiency potential vs established standard.

If you want help translating this into a cart with the right sizes, coils, and parts, start at The Furnace Outlet. We’ll walk it with you like a good neighbor step by step, no guesswork.