HeatSpec Guide

Certified systems / LG

LG KUSAE121A

Matched with the KNSAE121A indoor unit, this system is certified by ENERGY STAR but not to the cold-climate criteria and publishes 8.50 HSPF2 and 18.00 SEER2, with 8,400 BTU/h of heating at 5°F.

Heating capacity of the LG KUSAE121A at three outdoor temperatures, in BTU per hour. Paired with KNSAE121A: 8,400 at 5°F, 8,000 at 17°F, 12,000 at 47°F.

Not cold-climate certified. Paired with KNSAE121A. Points are the only three heating capacities the dataset publishes for this system; the lines between them are drawn to join those points and are not measurements. ENERGY STAR Certified Heat Pumps, retrieved 2026-10-16.

What these numbers are and are not. SEER2, EER2, HSPF2 and the COP at 5°F are results from a standard rating procedure, measured at fixed temperatures and airflow in a laboratory. They are not predictions for your house, your climate or your winter. Two systems with the same HSPF2 can use different amounts of electricity in the same building, and the same system will perform differently in Boston and in Atlanta. Use the published capacity at 5°F to judge whether a system still produces heat on a cold night; use HSPF2 only to compare systems with each other.

LG KUSAE121A published specifications

Every figure below is the value the dataset publishes for ENERGY STAR ID 3555706. Nothing is calculated except the two rows marked as ours.
Outdoor unitKUSAE121A
Indoor unitKNSAE121A (KUSAE121A)
Cold-climate certifiedNo
ENERGY STAR Most EfficientNo
SEER218.00 Btu/Wh
EER212.00 Btu/Wh
HSPF28.50 Btu/Wh
Cooling capacity11,000 BTU/h
Heating capacity at 47°F12,000 BTU/h
Heating capacity at 17°F8,000 BTU/h
Heating capacity at 5°F8,400 BTU/h
COP at 5°F1.70
Compressor stagingContinuously variable
RefrigerantR-32
Date certified2026-09-30
ENERGY STAR ID / AHRI reference3555706 / 214931166
5°F capacity as a share of 47°F (ours)70.0%
Capacity class (ours)12,000 BTU/h nominal

Source. ENERGY STAR Certified Heat Pumps, U.S. EPA, retrieved 2026-10-16 from the dataset's Socrata API. Record identified by ENERGY STAR ID 3555706, AHRI reference 214931166. Certification partner: LG Electronics, Inc.. Model numbers are reproduced exactly as published, including the asterisks ENERGY STAR carries as the manufacturer's wildcard for trim variants.

What the published capacities say about cold weather

A heat pump moves heat from outdoor air, so the colder that air gets, the less heat there is to move. The dataset publishes capacity at three outdoor temperatures, and the shape between them is the single most useful thing on this page. For the KUSAE121A paired with the KNSAE121A:

ENERGY STAR does not list this system under its cold-climate criteria. It is still a certified heat pump; it simply was not certified against the program's additional low-temperature requirements. In a cold climate that makes the published 5°F capacity above, and any backup heat you plan for, the numbers to look at.

Running cost for a 12,000 BTU/h system like this one

Worked as an illustration, not a quote: a house that burned 600 therms of gas in a year through an 80% AFUE furnace needed about 48.0 million BTU of delivered heat. At $1.50 a therm that gas cost $900. Delivering the same heat with a heat pump rated at 8.50 HSPF2 takes 5,647 kWh, which at $0.18 a kWh costs $1,016. The two costs are equal at $0.159 a kWh.

Those four prices are not your prices, and HSPF2 is a rating-condition figure rather than a seasonal measurement for your climate. Change every input in the running-cost calculator, which shows each formula as it works.

Comparable systems

Same nominal capacity class (12,000 BTU/h), closest published HSPF2 to this one. Colour marks cold-climate certification.

More: all 92 certified systems, or the explainer on SEER2 vs HSPF2.