Lennox 3WPD036S6S-1P*
Matched with the 3WMD036S6-1P indoor unit, this system is certified to the ENERGY STAR cold-climate criteria and publishes 9.00 HSPF2 and 20.00 SEER2, with 36,000 BTU/h of heating at 5°F.
Heating capacity of the Lennox 3WPD036S6S-1P* at three outdoor temperatures, in BTU per hour. Paired with 3WMD036S6-1P: 36,000 at 5°F, 26,600 at 17°F, 40,000 at 47°F.
- HSPF29.00Btu/Wh, seasonal heating
- SEER220.00Btu/Wh, seasonal cooling
- COP at 5°F1.80at that test point
- Capacity at 5°F36,000BTU/h
- Share of 47°F capacity90.0%ours: 5°F ÷ 47°F
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.
Lennox 3WPD036S6S-1P* published specifications
| Outdoor unit | 3WPD036S6S-1P* |
|---|---|
| Indoor unit | 3WMD036S6-1P (3WPD Mini-Split) |
| Cold-climate certified | Yes |
| ENERGY STAR Most Efficient | Yes |
| SEER2 | 20.00 Btu/Wh |
| EER2 | 12.00 Btu/Wh |
| HSPF2 | 9.00 Btu/Wh |
| Cooling capacity | 33,000 BTU/h |
| Heating capacity at 47°F | 40,000 BTU/h |
| Heating capacity at 17°F | 26,600 BTU/h |
| Heating capacity at 5°F | 36,000 BTU/h |
| COP at 5°F | 1.80 |
| Compressor staging | Continuously variable |
| Refrigerant | R-32 |
| Date certified | 2026-04-27 |
| ENERGY STAR ID / AHRI reference | 4577149 / 218193085 |
| 5°F capacity as a share of 47°F (ours) | 90.0% |
| Capacity class (ours) | 30,000 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 4577149, AHRI reference 218193085. Certification partner: Lennox Industries. 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 3WPD036S6S-1P* paired with the 3WMD036S6-1P:
- At 47°F it delivers 40,000 BTU/h.
- At 17°F it delivers 26,600 BTU/h.
- At 5°F it delivers 36,000 BTU/h, which is 90.0% of the 47°F figure.
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 30,000 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.