What a named furnace changes in heat pump ratings
Take the same outdoor unit and the same indoor unit, once with a furnace named in the listing and once without. In the 8,921 such pairs among rated split systems, the listing with the furnace shows a higher SEER2 in 90% of cases, by a median of 1.8, while its heating capacity at 5°F is lower in 73% of cases.
Where furnaces appear in the list
A certified match in the EPA data can name three things: an outdoor unit, an indoor unit and a furnace. Furnaces are a split-system affair. Of the 65,134 certified matches behind the 936 rated split systems, 58,526 name a furnace and 6,608 do not. Among mini- and multi-splits only 12 matches name one, and no single-package listing does.
Split systems fall into three groups: 473 rated products have matches with and without a furnace, 50 are listed only with a furnace, and 413 never name one. The first group makes a direct comparison possible: the same indoor model can appear in both kinds of listing.
The same pairing, with and without a furnace
To keep the comparison clean, this page only sets a listing with a furnace against a listing without one when the outdoor unit and the indoor model are identical. That leaves 8,921 pairs on 115 rated products. Each row below is the difference when the furnace is named. Each rated product counts once, through one of its model numbers.
| Rating | Median change with a furnace | Higher | Same | Lower |
|---|---|---|---|---|
| SEER2 | +1.8 | 90% | 3% | 6% |
| EER2 | +0.7 | 80% | 15% | 6% |
| HSPF2 | +0.1 | 54% | 33% | 13% |
| COP at 5°F | no change | 40% | 46% | 14% |
| Heating capacity at 47°F | −200 Btu/h | 22% | 26% | 52% |
| Heating capacity at 17°F | −600 Btu/h | 22% | 5% | 73% |
| Heating capacity at 5°F | −600 Btu/h | 21% | 6% | 73% |
The cooling ratings move most clearly. SEER2 is higher in 90% of pairs and EER2 in 80%. Taking each rated product once, the typical SEER2 gain is 1, smaller than the 1.8 across all pairs, since products with many pairs weigh more in that figure.
HSPF2 moves far less. It rises by a median of 0.1, and in 33% of pairs it does not change at all. Heating capacity goes the other way: at 5°F the listing with a furnace is lower in 73% of pairs, by a median of 600 Btu/h. The list gives the figures and not the reason, and this page does not guess at one.
By compressor type
The size of the SEER2 change depends on the compressor. Variable-speed split systems gain a median of 2.4, two-stage units 1.1 and single-stage units 0.8. Most of the pairs come from variable-speed products, so they set the overall figure.
| Compressor | Rated products | Pairs | Median SEER2 change | Median HSPF2 change | Median 5°F capacity change |
|---|---|---|---|---|---|
| Single-stage | 5 | 217 | +0.8 | 0 | −700 Btu/h |
| Two-stage | 15 | 2,550 | +1.1 | 0 | −600 Btu/h |
| Variable-speed | 95 | 6,154 | +2.4 | +0.3 | −400 Btu/h |
The cold-climate designation can change too
The EPA designation is published per match, so a furnace can sit on either side of it. In 5,111 pairs both listings carry the designation, and in 2,573 neither does. The two disagree in the remaining 1,237: in 1,056 of them only the listing without a furnace is designated, and in 181 only the listing with one. For a product with both kinds of match, its designation therefore says less than the designation of one pairing does.
Which match holds the headline figure
This site headlines the best match of each product, so it matters which kind of listing holds it. Of the 473 rated products with both kinds of match, the top SEER2 comes from a listing with a furnace in 196 cases and the top HSPF2 in 183. The top 5°F capacity comes from one in 258. Those counts do not repeat the pair results above: a product's best figure can come from an indoor model that has no twin in the other kind of listing.
A worked pair
The Johnson Controls HH836E2S11 has more such pairs than any other rated product, 948. With indoor unit CTF36B5CDS1, the listing without a furnace shows SEER2 15.2 and HSPF2 8.5; with furnace CP9C060B12MP13 it shows SEER2 17 and HSPF2 8.5. The pairing check lists both in one table.
Reading a listing with a furnace
These figures compare certified listings under test conditions. They say nothing about which system suits a building, how a furnace and heat pump share the work, or what either costs to run, and this site gives no advice on any of that. What the data does support is a narrower habit: when reading a rating, check whether it comes from a listing with a furnace, and compare it with a listing of the same kind.
Sources
- U.S. EPA, ENERGY STAR Certified Heat Pumps (data.energystar.gov, dataset 83eb-xbyy), certified as of 2026-10-27.
- Rating families, ratios, medians, ranks and class bands computed by heatpumpratings.online; see How the ratings are read.