HeatSpec Guide

Certified systems / LG

LG KUSAH121B

Matched with the KNSAH121B indoor unit, this system is certified to the ENERGY STAR cold-climate criteria and publishes 9.00 HSPF2 and 20.00 SEER2, with 8,400 BTU/h of heating at 5°F.

Heating capacity of the LG KUSAH121B at three outdoor temperatures, in BTU per hour. Paired with KNSAH121B: 8,400 at 5°F, 8,000 at 17°F, 12,000 at 47°F.

Cold-climate certified by ENERGY STAR. Paired with KNSAH121B. 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 KUSAH121B published specifications

Every figure below is the value the dataset publishes for ENERGY STAR ID 4430140. Nothing is calculated except the two rows marked as ours.
Outdoor unitKUSAH121B
Indoor unitKNSAH121B (KUSAH121B)
Cold-climate certifiedYes
ENERGY STAR Most EfficientYes
SEER220.00 Btu/Wh
EER212.30 Btu/Wh
HSPF29.00 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°F1.80
Compressor stagingContinuously variable
RefrigerantR-32
Date certified2026-09-30
ENERGY STAR ID / AHRI reference4430140 / 217485854
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 4430140, AHRI reference 217485854. 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 KUSAH121B paired with the KNSAH121B:

ENERGY STAR lists this system as meeting its cold-climate criteria, which the program describes as better low-temperature heating performance, suitable for use as a home's sole heating source. That is the program's judgement on the published test data, not a promise about any particular winter or any particular house.

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 9.00 HSPF2 takes 5,333 kWh, which at $0.18 a kWh costs $960. The two costs are equal at $0.169 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.