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.

13 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

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