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HVAC 101

What Is HSPF2?

HSPF2 (Heating Seasonal Performance Factor 2) measures how efficiently a heat pump heats over a full season: the higher the number, the less electricity it uses per unit of warmth. It's the winter counterpart to SEER2, which grades the cooling side of the same machine. The Lennox heat pumps we install run from 7.5 HSPF2 in the value tier to 10.5 in the flagship. In South Louisiana's short heating season, it's also the less important of the two ratings, and it's worth understanding why before you pay for more of it.

The Winter Half of the Label

A heat pump earns two efficiency ratings because it works two jobs. SEER2 grades the cooling season. HSPF2, short for Heating Seasonal Performance Factor 2, grades the heating season: the total heat delivered across a winter of mixed weather, divided by the electricity consumed to deliver it. Higher is better on both scales, and you’ll find both numbers on the yellow EnergyGuide sticker and on every spec sheet we quote from.

The number deserves a moment’s appreciation. Because a heat pump moves heat in from the outdoor air instead of making it from fuel, it routinely delivers more heat energy than the electricity it draws. HSPF2 captures how well that advantage holds up across a whole season, cold snaps included.

Why There’s a 2 on the End

In 2023 the Department of Energy retired the original HSPF test in favor of one run under conditions closer to a real installation, with realistic duct resistance instead of ideal lab airflow. Same machine, harder exam, lower score. The changeover hit the cooling rating at the same time, which is how SEER became SEER2; we covered that half of the story separately. The practical takeaway is simple. Compare HSPF2 to HSPF2, because an old brochure’s HSPF number will flatter a unit that a current model quietly outperforms.

What Real Equipment Scores

New split-system heat pumps start at the federal minimum of 7.5 HSPF2. The Lennox lineup we install runs from 7.5 HSPF2 at the value end to 10.5 HSPF2 in the flagship, and the pattern in between is consistent: the stronger heating numbers arrive bundled with variable-speed compressors and the highest SEER2 ratings, while the mid-tier models land between the bookends on both scales. You almost never buy HSPF2 by itself. It rides along with the cooling performance and comfort features that define the upper tiers in the first place.

How Much Weight to Give It in Acadiana

Less than SEER2, and it isn’t close. Our heating season amounts to a stretch of cool mornings and a few real cold snaps somewhere between Thanksgiving and Mardi Gras, while the cooling season runs roughly eight months. A rating that governs the short season can’t move your annual bill the way the one governing the long season does. So shop in that order: choose the SEER2 level and staging you want, then let HSPF2 break ties between finalists. Any current heat pump will carry a Louisiana winter without drama, with auxiliary heat strips standing by for the rare hard freeze. If a heat pump is on your short list for the next replacement, our heat pump installation page covers how we handle them, and we’re glad to talk through your house at (337) 893-5646.

Quick Questions

What's the difference between HSPF and HSPF2?
Same measurement, tougher test. In 2023 the Department of Energy replaced the old lab procedure with one that mimics real-world ductwork conditions, and the same equipment scores lower on it. So don't compare an old HSPF figure against a new HSPF2 figure directly; the older number will look better than it deserves to.
What HSPF2 rating should I look for in Louisiana?
New split-system heat pumps start at the federal minimum of 7.5 HSPF2, and in our climate that does the job. The heating season here is too short for a higher rating to change your annual bills much. Put your attention on SEER2 instead; that's the rating on duty eight months a year.
Is a high HSPF2 worth paying extra for here?
Rarely on its own. The flagship units that reach 10.5 HSPF2 also carry the best SEER2 ratings and variable-speed comfort, so the heating number mostly rides along with things you wanted anyway. If two systems are otherwise close, pick the better SEER2 and don't lose sleep over half a point of HSPF2.
Does HSPF2 apply to gas furnaces?
No. Furnaces are rated by AFUE, the percentage of the fuel's energy that ends up as heat in your house. HSPF2 belongs to heat pumps alone, because they move heat instead of making it. If you're choosing between the two, our heat pump vs. furnace explainer walks through the whole decision.

Keep Learning

Heat Pump vs. Furnace in Louisiana

For most South Louisiana homes a heat pump wins: mild winters, one system for both seasons. And an honest look at when a gas furnace still makes sense.

What Is a Ton of Cooling?

One ton of cooling removes 12,000 BTU of heat per hour. What that means for sizing your Louisiana home's AC, and why bigger isn't better here.

Single-Stage vs. Variable-Speed AC

Single-stage, two-stage, or variable-speed AC: how each one runs, and why longer, lower cycles win the humidity fight in a Louisiana cooling season.

Lennox Lineup

Every model we install, with SEER2 and HSPF2 specs listed.

Heat Pump Installation

How heat pumps handle Louisiana winters, and how we install them.

Rather Have a Person Explain It?

Our technicians have been walking Acadiana homeowners through their systems since 1956. Call (337) 893-5646 or schedule a visit, and bring your questions.

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