Ratings

Decoding the ratings on the label

What a contractor's quote sheet actually means, and the three mistakes, mismatched equipment, oversizing, and leaky ducts, that quietly erase an efficiency upgrade.

Decoding the ratings on the label

Every quote you get will be full of acronyms. There are only four that matter, and each one answers a different question.

SEER2

Cooling efficiency

Cooling delivered per watt-hour over a season. Minimum is 13.4–14.3 depending on region; 17–20 is high efficiency.

HSPF2

Heating efficiency

The same idea for the heating season. 7.5 is the federal floor for split systems; 9–11 is the premium tier.

COP

Efficiency right now

Heat out ÷ electricity in at one specific outdoor temperature. COP 3 means 300%. It falls as it gets colder outside.

Tons

Capacity, not weight

One ton = 12,000 BTU/h. Sizing should come from a Manual J load calculation, not a rule of thumb.

Rough capacity by home size

A sanity check on a contractor's proposal, not a substitute for Manual J.

Square feet

Size

750 – 1,000

1.5 – 2 tons

1,050 – 1,400

2.5 tons

1,450 – 1,700

3 tons

1,750 – 1,900

3.5 tons

1,950 – 2,200

4 tons

2,250 +

5 tons

Three things that quietly ruin efficiency

Mismatched indoor and outdoor units

Ratings are earned by a specific pair. Mix and match and you won't get the number on the label.

Oversizing

A too-big system short-cycles: worse humidity control, more wear, no efficiency benefit.

Leaky or undersized ducts

Duct losses of 20–30% are common in older homes and wipe out most of an efficiency upgrade.

Why the label number and your real bill can differ

SEER2 and HSPF2 are lab ratings earned by a specific, matched condenser-and-coil pairing under standardized conditions. Your actual bill also depends on duct condition, how correctly the system was sized, your thermostat settings, and your local climate, none of which show up on the spec sheet. That's why the savings calculator asks for your own electricity rate and run hours instead of quoting a single national number.