HSPF Rating Explained: How Efficient Are High HSPF Heat Pumps?

When it comes to heating devices, there is no single specification more important than the HSPF rating.

HSPF rating is the key metric for all heating devices; be it heat pumps, furnaces, or water heaters.

Understanding it gives you the fundamental insight into all heating devices.

In fact, it’s so important that every larger heating device – below is an example of a mini-split heat pump – is required by law to include the HSPF rating:

energy guide hspf rating of heat pumps

HSPF stands for Heating Seasonal Performance Factor’. It is a metric that determines the overall energy-efficiency of heating devices in much the same way as the SEER rating for cooling devices.

It gives you an idea of how significantly will running such a heat pump impact your electricity bill. You can be looking at several $100 savings every heating season with a high HSPF rating heat pump.

AHRI defines HSPF as:

The total space heating required during the space heating season, expressed in BTU’s, divided by the total electrical energy consumed by the heat pump system during the same season, expressed in watt-hours.

(Source: AHRI)

Basically, the HSPF rating tells us how much heating effect (in BTUs) we will get per kilowatt-hour (kWh). Here are two practical examples:

  1. Heat pump with 8 HSPF will give us 8,000 BTUs of heat for every kWh.
  2. Heat pump with 10 HSPF will give us 10,000 BTUs of heat for every kWh.

Obviously, it’s much better to have a heat pump with a higher HSPF rating (in this case 10). Such a heating device will draw less energy for the same heating effect, and you will pay less in heating expenses. You can check out a list of the best mini-split heat pumps with the highest HSPF rating here.

In the following article, we will answer:

  1. How is the HSPF rating calculated?
  2. What is a good HSPF rating for heat pumps?
  3. How much electrical bill savings per season can you generate by choosing a device with a higher HSPF rating?

In the end, we made some calculations regarding the classic problem of “I know 10 HSPF heat pump is better than 8 HSPF heat pump, but 10 HSPF costs $3,000, and 8 HSPF costs $2,000.”

How Is HSPF Rating Calculated?

To understand it fully, we need to know how the HSPF rating is calculated. HSPF is a metric of energy-efficiency measured throughout the winter heating season. Every winter, we can measure:

  1. Electricity we spend on heating; the power use in kilowatt-hours.
  2. Heating effect we get; the heating capacity in BTUs.

Example: To heat out 1500 sq ft home during the 3-winter months (December, January, February), we spent 20,000 kWh. The heat pump powered by these kilowatt-hours produced a total of 160,000,000 BTU of heating effect.

Based on this, we can calculate the HSPF rating like this:

HSPF = Heating Effect (in BTU) / Electricity Spent (in Wh)

Be aware that we have to use watt-hours, not kilowatt-hours. The conversion is simple enough; 1 kWh = 1,000 Wh. If you use the numbers in our example, we get:

HSPF = 160,000,000 BTU / 20,000,000 Wh = 8

In short, the HSPF rating of such a heater is 8. How much did we spend on electricity? The US average price per kWh is $0.1319. We needed 20,000 kWh to warm our house. That comes to $0.1319 x 20,000 = $2,638 per heating season.

How much would we save if we used 10 HSPF units instead of 8 HSPF? In the case of 10 HSPF, we would have to use only 16,000 kWh instead of 20,000 kWh (8 HSPF). That would cost us $2,110.

Here is a quick summary of heating costs:

  • HSPF 8 = $2,638 per heating season in electricity costs.
  • HSPF 10 = $2,110 per heating season in electricity costs.

You can see that (in our example) higher HSPF 10 device produced $500 fewer electricity costs than lower HSPF 8 device. That’s the true power of energy-efficient heating, and it leads us to this point:

What Is A Good HSPF Rating For Heat Pumps?

Having a heat pump with a high HSPF rating is crucial. But what is a good heat pump HSPF rating?

In the US, the minimum federal HSPF rating for all units is 7.7. To earn an ENERGY STAR label, a heat pump achieves at least 8.5 HSPF (for mini-split heat pump systems) and 8.2 HSPF (single-phase heat pumps).

In short:

  • 7.7 HSPF is the minimum.
  • 8.5 HSPF is a good HSPF rating (earns an ENERGY STAR label).
  • There are heat pumps with 10 HSPF, or even higher.

To give you an idea of the difference in these HSPF ratings in the electricity dollars, we made some calculations. Let’s say that a 7.7 HSPF heat pump would need $1,000 for heating. How much would the 8.5 and 10 HSPF heat pumps need? Here is the cost calculation:

  • 7.7 HSPF = $1,000
  • 8.5 HSPF = $906
  • 10 HSPF = $770

As you can see, the 10 HSPF heat pump spends 23% less electricity for the same heating effect. In this case, that makes a $230 difference in favor of the 10 HSPF heat pump.

Bigger units can have higher HSPF ratings; multi-zone mini-split units are especially energy-efficiency in the winter. For example, in the list of the best 4 zone mini-split systems, you will find a heat pump with a 12+ HSPF rating.

How Much Can You Save By Buying Heat Pump With Higher HSPF Rating?

Several people have posed the following question, or thereabout, “I know 10 HSPF heat pump is better than 8 HSPF heat pump, but 10 HSPF costs $3,000, and 8 HSPF costs $2,000.”

Obviously, saving $1,000 seems like a good idea. But we need to be aware that the cost of any heat pump is comprised of:

Heat Pump (Total Cost) = Initial Cost Of Heat Pump + Electricity Costs

The real question is, does the lower running electricity costs justify the higher initial cost of a high HSPF heat pump. Some of you have requested an HSPF calculation that could explain that (and we’ve prepared it).

But let’s first look at one common example of two similar devices:

  1. 3 ton (36,000 BTU) heat pump with 8 HSPF that costs $2,000.
  2. 3 ton (36,000 BTU) heat pump with 10 HSPF that costs $3,000.

In 10 years, which one will be more financially viable?

Let’s first presume that the heating season lasts for 3 months, and you run the heat pump for 8 h per day, yielding 1000 working hours per season. Let’s also use the US national average kWh price of $0.1319.

Both devices generate 36,000,000 BTU of heating power. Knowing the HSPF rating, we can calculate how many kWh of electricity they burn using the following equation:

Electricity Spent = HSPF / Heating Capacity (BTU)

Here is how many kWh each device spends with the electricity dollar amount:

  • 8 HSPF spends 4,500 kWh. Electricity cost: $593.55.
  • 10 HSPF spends 3,600 kWh. Electricity cost: $474.84.

As you can see, every heating season, a 10 HSPF heap pump uses $118.71 less electricity. In 10 years, that’s $1187.10. So, the initial +$1,000 is well worth the extra cost, especially knowing this is a fairly conservative estimate.

HSPF rating is used to evaluate many types of mini splits. Here are some examples of spec-by-spec analysis in which HSPF rating was used as a contributing factor:

If you have any questions about the HSPF rating, you can use the comment section below and we will try to help you out.

25 thoughts on “HSPF Rating Explained: How Efficient Are High HSPF Heat Pumps?”

    • Hello Tom, heat pumps are usually used as an auxiliary means of heating in the winter. Heat pumps are a valid choice because they can be used both in summer (for cooling) and in winter (for heating).

      Reply
    • I have no choice because there is no natural gas service in my neighborhood. I have an 18 SEER/10 HSPF variable speed heat pump that was installed May 2019 and my power bills are about 40% less than they were with my old single stage heat pump system. My home is about 1400 square feet.

      Reply
      • Hello Ken, thank you for your insight. Recently, the mini-split heat pumps have gained in popularity quite a lot. Their heating efficiency is spectacular. There are dozens that have 10 HSPF. If you check the list of the best mini-split heat pumps here you can see that the most efficient ones have an HSPF rating of more than 11.

        Reply
      • If you don’t mind me asking, what did you pay for installation and what brand? And, was it a multi-zone mini-split or a standard system with an outside heat pump and indoor air handler with coil and back-up heat?
        Thank You!!

        Reply
  1. Heat pump with 8 HSPF will give us 8 BTU’s of heat for every kWh.
    Heat pump with 10 HSPF will give us 10 BTU’s of heat for every kWh.

    These 2 statements are incorrect with kWh there as you mentioned in following paragraphs.

    If there is no gas to choose, ASHP makes sense. But if gas supply exists, even 10 HSPF won’t make sense.
    1m3 NG makes 35kBtu which costs somewhere around 40cents
    with 10 HSPF ASHP, that would be 3.5kWh times 13.2cents, that is 46 cents
    Installation is not included, also how ASHP functions under -10C or even -20C is questionable.

    Reply
    • Hello Jeff, you’re correct, those calculations are theoretical, given the perfect conditions. In practice, the real output is affected by specific conditions like the ones you mentioned.

      Reply
      • Hi guys, so I was just going to do a quick calculator to compare NG (from the tankless gas combi unit I have) vs kWh (for the heat pump unit I’m looking to install).

        Do you already have that calculator somewhere on the site before I repeat the work, or some equivalent comparison I’m missing? Thanks!

        Reply
        • Hello Joey, that’s a great idea! We don’t have natural gas to kWh calculator but we can make one, thanks to your suggestion. The basic question is this: “How much natural gas does it take to produce 1 kWh?”. 1 kWh is equal to 3,412 BTU; so, how much natural gas do we need to produce 3,412 BTU?

          Let’s calculate a bit: 1 cubic foot of natural gas can produce 1,038 BTUs. So we need 3,412 BTU / 1,038 BTU per cubic feet = 3.3 cubic feet of natural gas. Natural gas has a density of about 0.05 lb/ft3. That means you require about 0.165 lb of natural gas to produce 1 kWh (at 100% efficiency). Hope this helps.

          Reply
    • That calculation leaves out the efficiency of gas heaters. Some heat goes up with the smoke and the vents lose heat to roof and basement. Also, gas companies tend to raise rates in the winter, often by factor of two or more. But most importantly, one can get renewables based electricity while gas burns into CO2 and recent findings say most cities are leaking about 5% of natural gas into the atmosphere.

      Reply
      • Hello Sy, that’s exactly right. With calculations, we can only manage a limited number of variables; the heat loss and volatile gas rates are, unfortunately, hard to quantify.

        Reply
    • Hello Shannon, the HSPF rating doesn’t depend on the SEER rating. SEER is for cooling and HSPF is for heating.

      Reply
  2. So, a 96% nat gas furnace would burn 1,666 Therms to produce the same 160,000,000 BTUs. I am currently paying $1.20/ therm. That would have cost $2,000 instead of the $2,638 you paid. Its even marginally cheaper than the 10 HSPF heat pump

    Reply
    • Hello Matthew, if you are paying only $1.20/therm, go for natural gas. That’s a very low price per therm, usually they are $2+ per therm.

      Reply
  3. I live in New England where the winters are cold and summers are hot. I own a 212 sq ft condo would the 12000 be a good replacement for both heating and cooling ?

    Reply
    • Hello Mary, usually you take 20 BTU per sq ft for AC and at least 30 BTU per sq ft for heating. In your case, 40+ BTU would be a good idea, yes. 12,000 BTU unit seems a bit oversized but it’s better to be safe than sorry.

      Reply
  4. It seems for both cooling and heating your main goal is to obtain two costs and compare the two for savings.

    Savings isnt a concern until I know “how much will it cost to operate this heating device”.

    I can convert btu to kwh and then can calculate the costs. But I have been told that normal btu to kwh convertion is not the correct way to obtain the true kwh usage of a mini split.

    Reply
    • Hi James, a valuable insight. You can check our article about how much does it cost to run a mini split here.

      You are correct about that BTU to kWh conversion. Namely, if mini splits would have 100% efficiency, you could do that. However, mini splits usually have 300%+ efficiency (Coefficient Of Performance is 3 or more). That’s because they don’t ‘burn’ electricity; they merely use it to pump the existing heat in or out. That’s why they are that much more efficient. Hope some of this helps in understanding how to think about mini split usage.

      Reply
  5. I don’t know how to make the most sensible comment, so I’ll ramble for a minute:

    One important factor left out of the discussion is the ambient conditions — the heat output of a heat pump depends on the temperature of the air around the outside unit (right?).

    So the HSPF should somehow be related to that air temperature. Maybe a way to do that would be based on degree days (of heating required) during the heating season.

    I agree that HSPF should be a general indication of heating efficiency (e.g., a 10 HSPF heat pump is better (more efficient) than an 8 HSPF heat pump in most climates, but neither will achieve the rated HSPF if the climate is too cold, for two possible reasons:

    * all heat pumps have a lower limit on the temperature at which they can extract heat — some modern ones can work down to -5 (or maybe even -10) degrees which probably covers most climates in the continental US, but below that temperature, some form of supplemental heat is required (often electrical resistance, which presumably has an HSPF of 3.412). This will require considerably more electricity during periods when the temperature is that low.

    * presumably, heat pump efficiency varies with the ambient temperature around the outside unit. For example, if you are trying to heat an area to 72 degrees F and the outside ambient is 68 degrees F, the unit will use less electricty (or run for a shorter “cycle” than when the outside ambient temperature is say 30 degrees F.

    (I don’t know exactly how that works, I’m guessing that the compressor uses more power because pressures are higher (or something) when outside temperatures are lower.)

    Anyway, I guess my main point is that if you really want to get an accurate estimate of heating costs for a given space, HSPF doesn’t tell the entire story. Yes, a higher HSPF unit will cost less to run than a lower HSPF unit, but HSPF, by itself will not let you calculate the actual expected heating costs.

    So, now my question — is there a chart, website, or some other resource that talks about and gives information on how the HSPF varies with ambient outside temperature?

    As a follow-up to my previous comment, I would add:

    If you are trying to compare the cost of NG (Natural Gas) to heat a space to that of a heat pump, you should consider that a given amount of NG will always produce a given amount of heat (BTUs) regardless of the ambient temperature, while with a heat pump, the kwhrs to produce a given amount of heat will vary with the outside temperature.

    (And, just to complicate things a little more:

    * Yes, the ambient temperature around the space to be heated will affect the heat loss from that space (and the number of BTUs required to heat it to a given temperature, ….

    * But, for a heat pump, the ambient temperature is sort of a “double whammy” (technical term 😉 — ambient temperature affects both (1) the BTUs required to heat the space to a given temperature, and (2) the number of BTUs provided by the heat pump per kwhr of electricity.

    Reply
    • Hi Bill, that was quite an interesting rant. It’s true, the heat pump efficiency depends on the outdoor temperature. This temperature vs heat pump efficiency article explains the situation quite well. HSPF is a standardized metric that tries to capture the real-life outdoor temperature conditions.

      Namely, the HSPF test procedure involves measuring heat pump energy efficiency at:
      – 47 degrees (47°F) for high temperature testing.
      – 17 degrees (17°F) for low temperature testing.
      – 35 degrees (35°F for frost accumulation testing.

      In short, the HSPF rating does try to emulate the real-time ambient conditions as much as possible.

      At lower and lower outdoor temperatures, the efficiency will be lower and lower. This efficiency it measured primarily by COP or Coefficient of Performance. It does not change HSPF rating, because HSPF rating is measured in laboratory testing.

      At very low temperature (below freezing), the gas furnaces, for example, will have the same efficiency while the heat pump efficiency will be decreasing. At some point, it will be better (more financially viable) to start heating with gas instead of with electricity. That’s why many homeowners have a heat pump with a furnace backup. At very low temperatures, the furnace comes online while the heat pump shuts off.

      I hope this at least gives some insight. All your points are quite on point.

      Reply
  6. I am weighing the options between a 18,000 btu mini split and a 35,000 btu gas vented fireplace to heat a roughly 500 sq. ft. room. The gas vented fireplace is 76% efficient. Would a mini split be more economical to heat with current electric rates being 9-10 cents per Kwh vs gas rates of .75 per therm (but projected to increase by 50%)..

    Reply
    • Hi Jeff, electricity price of 9-10 cents per kWh is very low; that’s why an 18,000 BTU mini split would be a better choice. The problem is if you live in the northern US. The efficiency of mini splits (Coefficient Of Performance) decreases with the temperature. Nonetheless, with gas prices projected to increase so much, a mini split really has an advantage here. If you need some suggestions, this MrCool 18,000 BTU unit would be perfect because it has a high 10 HSFP efficiency and runs efficienctly in low temperatures as well.

      Reply
      • Thank You. What is funny about that is in our area we usually stick with gas appliances because natural gas is/was cheaper. Looking at national averages I see we are low for electric right now.
        I am looking at the MrCool 18000 BTU 4th generation unit which boast a HSFP of 11.5 but living in northwest PA, which I think is considered a zone 5 lowers that to a HSFP 9. Looking at our average monthly temps (on my gas bill) we are generally between 28F to 38F with the exception of February which is typically 19 – 20. There have been times we dip below 0 but not that often. I believe this unit says -13. Is it safe to assume that this would work fine in my climate?
        I followed your formula and used the calculator to see what average would be on electric use but get lost on comparing to usage of gas and therms.

        Reply
        • Hi Jeff, these energy prices are through the roof and volatile, making a good calculation for the next 10-20 years much harder. But, yes, heat pumps like the MrCool 18k are definitely a go-to choice when living in warmer climates. With the 3rd and now 4th generation, you will get a high efficiency at lower temperatures as well. As you have adequately pointed out, it all depends on the price of electricity vs the price of gas.

          That -13F. Yes, the unit will work fine, the more important part is how efficient it will be. As we have pointed out in our article about heat pumps and temperature relationship here, a heat pump can be more than 300% efficient at 40F (Coefficient Of Performance is above 3.0) but at low temperatures, it can fall down to 100% or even below. The low-temperature heat pumps like MrCool 4th generation will still be efficient at 0 degrees but at -13F, the efficiency can fall off the cliff. Nonetheless, heat pumps are the future and a good choice, especially with the rising costs of gas. Hope this helps.

          Reply

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