SEER, AFUE, HSPF Explained: Understanding HVAC Efficiency Ratings

When shopping for HVAC equipment, you'll encounter efficiency ratings. Here's what they actually mean.

Air Conditioner Ratings

SEER (Seasonal Energy Efficiency Ratio) Measures cooling efficiency over a typical cooling season. Higher = more efficient.

• Minimum legal: 14-15 SEER (varies by region)
• Standard efficiency: 14-16 SEER
• High efficiency: 17-21 SEER
• Ultra-high efficiency: 21+ SEER

SEER2 A newer testing standard introduced in 2023. SEER2 numbers are about 4.5% lower than equivalent SEER numbers due to stricter testing conditions. A 14.3 SEER2 unit is roughly equivalent to a 15 SEER unit.

EER (Energy Efficiency Ratio) Measures efficiency at a specific condition (95°F outdoors). Useful for very hot climates but less relevant for the Bay Area.

Furnace Ratings

AFUE (Annual Fuel Utilization Efficiency) Percentage of fuel that becomes heat. The rest goes up the flue.

• Old furnaces: 56-70% AFUE
• Standard efficiency: 80-83% AFUE
• High efficiency: 90-98% AFUE

A 95% AFUE furnace converts 95% of the gas to heat. Only 5% is lost.

Heat Pump Ratings

HSPF (Heating Seasonal Performance Factor) Measures heating efficiency over a season. Higher = more efficient.

• Minimum: 7.7 HSPF
• Standard: 8-9 HSPF
• High efficiency: 10+ HSPF

HSPF2 The newer standard, similar to SEER2. Numbers are about 4.5% lower.

Heat pumps also have SEER ratings for cooling mode.

What Should You Buy?

Consider Your Usage If you barely use AC, paying for 21 SEER might not make sense. If you cool heavily, higher efficiency pays off faster.

Do the Math The efficiency difference between a 16 SEER and 20 SEER AC might save $100-200/year. If the higher efficiency unit costs $1,000 more, that's a 5-10 year payback.

Climate Matters In the Bay Area's mild climate, you might use less heating and cooling than other regions, extending payback periods on high-efficiency equipment.

Don't Overlook Installation Even the most efficient equipment underperforms if installed poorly. A properly installed 16 SEER system can outperform a poorly installed 20 SEER system.