SEER2, HSPF2, AFUE — What These Numbers Actually Mean

HVAC equipment comes with a soup of acronyms and numbers that are supposed to help you make a smart decision. Here's what they actually tell you — and what they don't.

The one thing all these ratings have in common

They all answer the same basic question: how much of the energy you pay for turns into actual heating or cooling? A higher number is always better. That's it. Everything else is details.

SEER2 — cooling efficiency

What it stands for: Seasonal Energy Efficiency Ratio 2

What it measures: How efficiently the system cools your home over an entire cooling season — not just at peak performance, but across the full range of summer temperatures.

What the numbers mean in practice:

• 14–15 SEER2 — Meets current minimum federal requirements. Functional, affordable, nothing special.
• 16–17 SEER2 — The sweet spot for most Western Washington homes. Noticeably lower cooling costs than a baseline system.
• 18–20 SEER2 — Premium efficiency. You'll see the savings, especially as our summers keep getting warmer. These systems typically qualify for the highest PSE rebate tier ($600).

The real-world difference: Replacing a 10-year-old 13 SEER system with a new 18 SEER2 system can reduce your cooling costs by roughly 30–40%. That's not a manufacturer's marketing claim — it's basic math. You're getting the same cooling from significantly less electricity.

What SEER2 doesn't tell you: How well the system heats. A high SEER2 rating says nothing about heating performance. For that, you need HSPF2.

HSPF2 — heating efficiency (heat pumps)

What it stands for: Heating Seasonal Performance Factor 2

What it measures: How efficiently a heat pump heats your home across the full heating season, including colder days when the system has to work harder.

What the numbers mean in practice:

• 7.5–8.5 HSPF2 — Standard efficiency. Gets the job done, but you'll feel it on your electric bill during January.
• 8.5–9.5 HSPF2 — Good efficiency. Solid performer for our climate.
• 9.5–10.5+ HSPF2 — High efficiency, cold-climate rated. These systems maintain strong heating output even as outdoor temps drop. Most qualify for Energy Star and the highest PSE rebate tiers.

Why this number matters more than SEER2 in Western Washington: We heat our homes 8–9 months of the year. We cool them for maybe 2–3. Your heating efficiency rating has a much bigger impact on your annual energy costs than your cooling rating. When comparing heat pumps, pay more attention to HSPF2 than SEER2.

Cold climate certification: Systems with HSPF2 of 9.5+ and SEER2 of 16+ typically earn Cold Climate Heat Pump certification, meaning they've been tested and verified to perform well in colder conditions. For homes in the foothills — Enumclaw, Buckley, Greenwater — this designation is worth paying attention to.

AFUE — furnace efficiency

What it stands for: Annual Fuel Utilization Efficiency

What it measures: What percentage of the fuel your furnace burns actually becomes heat in your home. The rest goes up the flue as exhaust.

What the numbers mean in practice:

• 80% AFUE — For every dollar of gas you burn, 80 cents heats your home and 20 cents goes out the exhaust vent. These are standard-efficiency furnaces with conventional venting.
• 96% AFUE — 96 cents of every dollar heats your home. These are condensing furnaces that extract extra heat from exhaust gases. They require different (PVC) venting.
• 97–98% AFUE — Top-tier efficiency. The Carrier Infinity series hits 98%, meaning virtually all the fuel becomes usable heat.

The 80% vs. 96% decision: This isn't always just about efficiency. If your home currently has an 80% furnace with standard metal flue venting, upgrading to a 96%+ system means installing new PVC condensate venting. That's usually straightforward, but it adds to the installation scope. If you're replacing an existing 80% furnace and your venting is in good shape, sometimes staying at 80% with a better blower motor and controls is the smarter financial move. It depends on your home — and that's exactly the kind of thing we assess during an in-home estimate.

One thing to note: AFUE only measures the furnace's gas-to-heat conversion. It doesn't account for heat lost through your ductwork. A 98% AFUE furnace connected to leaky ducts is still wasting energy — just not at the furnace itself.

EER2 — peak cooling efficiency

What it stands for: Energy Efficiency Ratio 2

What it measures: How efficiently the system cools at a specific high temperature (95°F outdoor, 80°F indoor). This is peak-load performance, not seasonal average.

When it matters: Honestly, for most Western Washington homeowners, EER2 is the least important of the four ratings. We don't spend many hours at 95°F. It matters more in Phoenix than Puyallup. That said, a higher EER2 does indicate the system handles heat spikes well — and with the heat events we've seen in recent summers, it's not a bad tiebreaker when comparing similar systems.

The bottom line

When you're comparing systems, here's the cheat sheet:

If you're buying a heat pump: Look at HSPF2 first (heating efficiency matters most here), then SEER2 (cooling), then EER2 (peak cooling). Higher numbers in all three = lower energy bills.

If you're buying a gas furnace: AFUE is your number. 96%+ saves real money over the life of the system, but 80% can still be the right call depending on your home's venting setup.

If you're buying a dual fuel system: You're looking at both — HSPF2/SEER2 for the heat pump side, and AFUE for the furnace side.

And if the numbers start blurring together, just ask us. We'll show you what each option means for your specific home and your specific energy costs — not in acronyms, but in dollars.