Ten flagship ducted lineups, measured against the federal minimum — not marketing claims.

Why this page uses "SEER2" instead of the plain "SEER" you might expect

Every rating on this page uses the letters SEER2 rather than just SEER — and that's not a typo or a downgrade. SEER2 is simply the current, more realistic version of the same cooling-efficiency test, in effect since 2023. Regulators at AHRI (the Air-Conditioning, Heating, and Refrigeration Institute, the industry group that runs the official lab tests every manufacturer has to pass) discovered the old test was too easy — it let equipment run in conditions friendlier than a real house with real ductwork ever sees. So they toughened it up, and that tougher test knocks about 5–7% off the score for the exact same physical equipment (SEER2.com; AHRI, 2023 Energy Efficiency Standards). Practically speaking, that just means one rule: judge every number on this page only against the other numbers on this page (or any other current SEER2 figure) — never against an old SEER number from a purchase, a brochure, or a memory of a unit from a few years back, since those come from an easier test and will look artificially better by comparison.

What EER2 means, and why it's worth knowing

EER2 (Energy Efficiency Ratio 2) measures the same thing as SEER2 — how much cooling a unit produces per dollar of electricity — but on one specific, brutally hot afternoon instead of averaged across a whole summer. Think of SEER2 as a car's combined MPG rating and EER2 as its mileage at highway speed on the hottest day of the year: SEER2 tells you what to expect on average; EER2 tells you what to expect when it matters most, like a 95°F heat wave when your air conditioner is working its hardest and your electric bill is highest. It matters most in hot, humid climates where summer afternoons regularly push equipment to its limit — a unit with a strong SEER2 but a weak (or unpublished) EER2 could still struggle, and cost more to run, exactly when you need it most. Of the ten flagship models compared here, only five publish an EER2 figure at all: Lennox leads at 13.2 EER2, followed closely by Carrier at 13.0. York and Bosch trail at 12.0 EER2 — still solid, but Lennox holds up noticeably better on that one brutal afternoon. Trane, American Standard, Goodman, Daikin, and Mitsubishi Electric don't publish an EER2 number for their flagship at all, which is a disclosure gap rather than evidence of a low score — worth asking a contractor for directly if peak-heat performance matters in your climate.

The models here are all "Most Efficient" — not just above average

Every model in this comparison qualifies for ENERGY STAR Most Efficient, a tier well above ENERGY STAR's regular certification and considerably above the federal minimum of 14.3 SEER2 / 7.5 HSPF2 (ENERGY STAR, Most Efficient 2025 criteria). In short: these are the cream of the crop. The comparison below looks at how these top-tier units differ from each other on installed cost, modulation (how smoothly a unit can throttle its output up or down), and — most importantly — the actual economics of owning one.

Modulation: Good, Better, Best

Modulation is how smoothly a unit can throttle its output in small steps rather than snapping between "on" and "off." It's a separate story from SEER2 and HSPF2 — those measure how efficient the equipment is; modulation measures how well it matches its output to what a room actually needs at any given moment, which avoids the energy waste of repeatedly blasting on and shutting off. Two things decide the tier below: turndown ratio (how far a unit can throttle down from full capacity — lower is better, since it means the unit can idle down for a mild day instead of overshooting) and speed increments (how fine-grained those adjustments are).

What the numbers show

A few patterns hold across the ten flagship lineups researched for this page:

• The spread between #1 and #10 is wider than it looks at first glance. Carrier's Infinity 23/27VNA3 tops the list at 23.0 SEER2, roughly 21% above Bosch's IDS Ultra at 19.0 SEER2 — and both are premium, variable-capacity flagship products, not budget units.
• Modulation range is a separate efficiency story from SEER2 — and both matter. SEER2 measures one thing: how much cooling (or heating, for HSPF2) a unit squeezes out of a fixed amount of electricity in lab testing. How smoothly a unit can throttle its output — in small, gradual steps rather than just "on" or "off" — is a different kind of efficiency, because it avoids wasted energy from constantly cycling on and off at full power for a small heating or cooling need. Lennox and Bosch both advertise 1% modulation increments across wide turndown ranges (Bosch to 33% of full capacity), while several other flagship units modulate in coarser steps. The two ratings are independent of each other, and a unit's real-world, day-to-day efficiency depends on both.
• Installed cost doesn't track SEER2 in a straight line. Goodman's GZV9S posts a strong 21.0 SEER2 at an installed cost roughly 40–60% below several competitors rated similarly or lower — a reminder that brand positioning and dealer network pricing move installed cost as much as the compressor technology inside the unit.

How high-efficiency heat pumps impact the economics

1. You pay a real premium upfront — but a smaller one than you'd expect. The ten flagship heat pumps above average roughly $11,100 installed. A like-for-like 80–90% AFUE (Annual Fuel Utilization Efficiency — the furnace equivalent of SEER2) gas furnace paired with a central air conditioner runs roughly $9,800–$11,000 installed by independent cost estimators (CostCandor's HVAC replacement calculator), consistent with our own Chicago case study — putting the realistic premium at roughly 0–15%, well below the 30%+ gap often assumed, mostly because a genuinely high-efficiency furnace-and-AC combo isn't cheap either. What that premium buys is a large efficiency jump: converting the table's average HSPF2 (9.8) into a coefficient of performance (COP — the ratio of heat delivered to electricity consumed) works out to roughly COP 2.9 (HSPF2 ÷ 3.412), meaning the heat pump delivers about 2.9 units of heat for every unit of electricity it uses, or roughly 290% efficient. A 90% AFUE furnace delivers, by definition, 0.9 units of heat per unit of fuel — 90% efficient. That's a gap of roughly 200 percentage points in raw heating efficiency. It's an efficiency comparison, though, not a cost comparison, since electricity and gas are priced on entirely different scales — which is exactly why climate and local utility rates, not the rating alone, decide whether that efficiency pays off. That's the subject of the next two points.
2. In a Northern climate like Chicago, that efficiency edge usually isn't enough to beat gas on cost. Our own Chicago case study found a cold-climate heat pump running $13,756 more over 10 years than simply replacing an aging furnace and AC in kind — driven mainly by ComEd's roughly 24¢/kWh electricity rate against Illinois's cheap $1.48/therm gas (Chicago case study). For this reason, the more economically feasible setup for most Chicago-area homes is usually a dual-fuel (hybrid) system: pairing a 20 SEER2 heat pump with a 90% AFUE gas furnace. The heat pump handles all the cooling and delivers cheap, highly efficient electric heat during the mild spring and fall — generally above about 35°F outdoors — while the system automatically switches to the gas furnace once a deep Chicago freeze pushes temperatures below that point, where gas heat is cheaper to run. In the all-electric scenario, over a 15-year ownership horizon, an Inflation Reduction Act-funded rebate would generally be needed to close that cost gap — and as of this writing, Illinois's IRA-funded rebate programs are still pending federal approval and haven't opened to homeowners yet (Illinois EPA).
3. Milder climates with lower electricity rates, like St. Louis, tend to flip this math in the heat pump's favor. Ameren Missouri's residential electricity rate runs around 13–14¢/kWh — roughly half of the ComEd rate that drove the Chicago result above (Ameren Missouri rate information). A lower electric rate directly narrows or reverses the heating-cost gap, and St. Louis's milder winters mean a heat pump spends more of the year running efficiently rather than deep in cold-climate backup mode — which is also where modulation capability (see above) earns its keep, capturing savings across the long stretches of partial heating and cooling load a milder climate produces. This is a directional read rather than a full case study; local gas prices and equipment choice will move the actual numbers, so run your own ZIP code through the comparison calculator rather than treat this as a guarantee.