Clement Boston Heat Pumps gets asked about SEER2 and HSPF2 ratings on almost every estimate, usually because two quotes list different numbers. This guide explains what each rating measures, which ones change your comfort and bills in a Boston winter, and how to read them on a spec sheet without overpaying for a tier you won’t notice.
The three numbers on a heat pump label
Each rating answers a different question: SEER2 is cooling over a summer, HSPF2 is heating over a winter, and COP is heating at one outdoor temperature.
| Rating | What it measures | Units | What it tells you |
|---|---|---|---|
| SEER2 | Cooling delivered over a test summer, divided by electricity used | BTU per watt-hour | How cheaply it cools |
| EER2 | Cooling at one hot condition (95°F outdoors) | BTU per watt-hour | How it handles a heat wave |
| HSPF2 | Heating delivered over a test winter, divided by electricity used | BTU per watt-hour | Average heating efficiency |
| COP | Heat out divided by electricity in, at one temperature | A plain ratio | Heating efficiency on a specific night |
The federal minimum for a new split-system heat pump is 14.3 SEER2 and 7.5 HSPF2. Every cold-climate unit sold for a Massachusetts house clears that easily, so the minimums rarely decide anything here.
SEER2: the cooling number
SEER2 measures how much cooling a unit delivers for each watt-hour over a modeled summer. Higher means less electricity for the same cooling.
Why it matters less in Boston
Logan averages fourteen days a year at or above 90°F, and summer humidity matters more than peak heat. A heat pump that runs long, slow cycles pulls more moisture out of the air than a higher-rated unit that’s oversized and short-cycles. Sizing, which the sizing guide covers, does more for summer comfort than SEER2 points.
What the “2” changed
Since 2023, ratings use the M1 test procedure, which runs the equipment against higher external static pressure, closer to the resistance of real ducts. The same unit scores lower under SEER2 than it did under SEER.
That’s also why we measure static pressure in your ducts at the first visit. A duct system more restrictive than the test condition costs efficiency the label never shows, and duct testing and repair is how that gets fixed.
HSPF2: the heating season average
HSPF2 is the heating version of SEER2: heat delivered over a modeled winter, divided by electricity used. It’s useful for comparing units, but it’s an average, not a cold-night figure.
What it hides
The HSPF2 calculation weights mild and moderate weather heavily, because that’s where most heating hours fall. Two units can share an HSPF2 while one loses far more capacity at 5°F. In a house sized to Logan’s 7°F design temperature, or colder inland near Hanscom Field, that difference decides whether the backup heat runs.
COP and capacity at 5°F: the numbers that matter here
COP tells you how much heat you get for each unit of electricity at a stated temperature, and capacity tells you how much heat the unit can still deliver there.
| Figure | ENERGY STAR cold-climate floor | Why it matters |
|---|---|---|
| COP at 5°F | At least 1.75 | Running cost on the coldest nights |
| Capacity at 5°F | At least 70% of the 47°F rating | Whether the heat pump carries the house without backup strips |
Electric baseboard has a COP of 1.0 at every temperature. A cold-climate heat pump at 1.75 or better on a 5°F night still delivers 75% more heat per kilowatt-hour, and far more on a 35°F day. See do heat pumps work in Massachusetts for how that plays out over a winter.
Why Mass Save cares
Mass Save’s heat pump rebates require equipment on the ENERGY STAR cold-climate list and its qualified products list. The cold-climate test is what makes a unit eligible; a high SEER2 alone does not. The rebate guide covers the rest of the conditions.
Efficiency tiers and what they buy
Manufacturers sell the same tonnage at two or three efficiency tiers. The step up usually buys a more finely modulating compressor and fan, not more heat on the coldest night.
- Entry cold-climate tier: meets the cold-climate floor; often fine for a well-sealed house with sound ducts.
- Mid tier: wider modulation, quieter low-speed operation, better part-load efficiency.
- Top tier: the highest SEER2 and HSPF2, often with a proprietary communicating thermostat.
The price gap between tiers is real, and the savings depend on your house, your rate and how you run it. We don’t promise a payback; we show the capacity at 5°F for each option on the estimate so the comparison is honest. Most cold-climate ducted units already modulate; see variable speed heat pumps.
When a higher tier earns its cost
A long cooling-heavy top floor, a house where noise at a tight lot line matters, or a home with no backup heat at all can justify the step up. A leaky house usually can’t: air sealing it first saves more than the tier would.
Reading a spec sheet or AHRI certificate
Ratings belong to a matched pair, not to the outdoor unit alone. The indoor coil or air handler changes the numbers.
- Find the AHRI reference number for the exact outdoor and indoor models being quoted.
- Check the listed heating capacity at 47°F and at 5°F, and the COP at 5°F.
- Confirm the pair appears on the ENERGY STAR cold-climate list.
- Compare SEER2 and HSPF2 last, and only against the same pairing on other quotes.
If one quote lists an outdoor unit with a mismatched or unnamed indoor coil, the ratings on it may not apply. That matters most on a heat pump replacement, where reusing an old air handler can quietly drop the system below its listed figures and out of rebate eligibility.
What we put on the estimate
Our written estimate lists the equipment pair and its capacity at 5°F, beside the load calculation for your house at your town’s design temperature. That’s the comparison that tells you whether a unit will heat the house.
If you’re weighing two quotes, our quote checklist lists the other lines to compare, and the cost guide shows how equipment choices move the price. For figures on your own house, call us or send the form.