AFUE measures furnace heating efficiency, SEER2 measures air-conditioner and heat-pump cooling efficiency, and HSPF2 measures heat-pump heating efficiency. In every case, a higher number means less energy wasted and lower operating cost. AFUE is a percentage; SEER2 and HSPF2 are ratios where bigger is better.
Quick answer
- AFUE = furnace heating efficiency (a %). 80% is standard; 90–98.5% is high-efficiency.
- SEER2 = cooling efficiency. New systems start around 14–15; high-efficiency runs 16–20+.
- HSPF2 = heat-pump heating efficiency. Higher is better; 8–10+ is strong.
- Higher ratings cost more upfront but cut monthly bills — the gap pays back over the system's life.
AFUE — furnace heating efficiency
Annual Fuel Utilization Efficiency tells you what share of the fuel a furnace turns into usable heat. An 80% AFUE furnace converts 80% of the gas to heat and vents the other 20%. High-efficiency condensing furnaces reach 90–98.5% AFUE by capturing heat from exhaust gases that a standard furnace throws away. In colder parts of Pennsylvania and western Maryland, the fuel savings from a 95%+ furnace add up quickly over a long heating season.
SEER2 and HSPF2 — the 2023 standard
SEER2 (Seasonal Energy Efficiency Ratio 2) rates cooling; HSPF2 (Heating Seasonal Performance Factor 2) rates heat-pump heating. The '2' versions replaced the older SEER/HSPF ratings in 2023 and are tested under higher static pressure that better reflects real ductwork, so the numbers run slightly lower than the old scale. For both, higher is better: a 20 SEER2 unit uses far less electricity to deliver the same cooling as a 14 SEER2 unit.
How to use the numbers when buying
Match the rating to how much you run the system. If you cool heavily in summer or heat with a heat pump all winter, a higher SEER2/HSPF2 pays back faster. If a room or system runs only occasionally, a mid-tier rating may be the better value. Compare the efficiency premium against estimated annual savings and available rebates — that's the real decision, not the headline number alone.
Common mistakes to avoid
Buying efficiency without fixing the ducts
A high-SEER2 system on leaky, undersized ductwork can't deliver its rated efficiency. Air leaks and restrictions waste the very energy you paid extra to save. Duct sealing and correct sizing come first.
Comparing old SEER to new SEER2
Because SEER2 is tested differently, you can't directly compare a SEER2 number to an older SEER label — the SEER2 figure looks lower for equivalent equipment. Always compare like-for-like.
How Comfort Central Inc. helps
- We quote efficiency options side by side with estimated operating-cost differences so you can see the payback, not just the sticker.
- Our installs are matched (indoor + outdoor) so the system actually achieves its rated SEER2 instead of an unverified mismatch.
- We help identify utility and manufacturer rebates that apply to higher-efficiency equipment in our service area.
Frequently asked questions
What is a good SEER2 rating?
New central systems generally start around 14–15 SEER2. 16–18 is solidly high-efficiency, and premium variable-speed systems reach 20+ SEER2. The right level depends on how much you cool and the payback in your climate.
Is a 96% AFUE furnace worth it over an 80%?
In a cold climate with a long heating season — like much of Pennsylvania and western Maryland — the fuel savings from a 90–96% furnace usually justify the higher upfront cost over the system's life. In milder areas the payback is slower.
Why did the ratings change to SEER2 and HSPF2?
The Department of Energy updated the test procedure in 2023 to use higher external static pressure, which more closely matches installed ductwork. The result is a more realistic rating, with numbers slightly lower than the old SEER/HSPF scale.
Written by: Merle Vaughn · Last updated: June 17, 2026