{"id":20206,"date":"2026-09-18T02:48:44","date_gmt":"2026-09-18T02:48:44","guid":{"rendered":"https:\/\/www.jnodenergy.com\/?post_type=news&p=20206"},"modified":"2026-09-18T02:48:45","modified_gmt":"2026-09-18T02:48:45","slug":"how-to-read-heat-pump-performance-data-at-low-outdoor-temperatures","status":"publish","type":"news","link":"https:\/\/www.jnodenergy.com\/fr\/nouvelles\/how-to-read-heat-pump-performance-data-at-low-outdoor-temperatures\/","title":{"rendered":"How to Read Heat Pump Performance Data at Low Outdoor Temperatures?"},"content":{"rendered":"\n

Heat pump performance data can tell you much more than the nominal capacity shown on a product nameplate. A heat pump rated at 9 kW does not necessarily deliver 9 kW when the outdoor temperature falls to -15\u00b0C.<\/p>\n\n\n\n

This is why heat pump performance data matters when selecting a unit for a cold-climate project. The capacity shown in a product name or basic brochure is normally based on a specific test condition. Change the outdoor temperature or the required water temperature, and the result can change.<\/p>\n\n\n\n

For installers, distributors, and project buyers, the useful question is simple: how much heat can the unit deliver under the conditions of the project?<\/p>\n\n\n\n

Using Heat Pump Performance Data for Cold-Climate Selection<\/h2>\n\n\n\n

When reviewing a performance table, check the outdoor temperature first.<\/p>\n\n\n\n

A unit may be rated at 9 kW under a mild test condition, but a building normally needs more heating when the weather is coldest. For equipment selection, the more useful figure is therefore the capacity available at the project’s design outdoor temperature.<\/p>\n\n\n\n

JNOD’s JMU90HC is a good example. It is a 9 kW R290 monobloc top-blow heat pump, but its published capacity changes as outdoor temperature falls.<\/p>\n\n\n\n

\"How<\/figure>\n\n\n\n

At 35\u00b0C outlet water, the published heating capacity is:<\/p>\n\n\n\n

Outdoor temperature<\/th>Heating capacity<\/th><\/tr>
5\u00b0C<\/td>9.10 kW<\/td><\/tr>
-15\u00b0C<\/td>6.86 kW<\/td><\/tr>
-25\u00b0C<\/td>5.61 kW<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The model name stays the same. The available heating output does not.<\/p>\n\n\n\n

So when a product is described as a \u201c9 kW heat pump\u201d, the next question should be:<\/p>\n\n\n\n

9 kW at what outdoor temperature and what water temperature?<\/strong><\/p>\n\n\n\n

For cold-climate sizing, PNNL recommends using extended manufacturer performance data and comparing the available capacity with the building’s design heating load rather than relying only on nameplate capacity. See PNNL’s cold-climate heat pump sizing guidance<\/a>.<\/p>\n\n\n\n

Check the Water Temperature<\/h2>\n\n\n\n

Outdoor temperature is only part of the picture.<\/p>\n\n\n\n

A heat pump supplying 35\u00b0C water is working under a different condition from the same unit supplying 55\u00b0C water. That difference matters for systems using underfloor heating, radiators, or mixed emitters.<\/p>\n\n\n\n

The JMU90HC data shows this clearly. At -15\u00b0C outdoor temperature, its published heating capacity changes to:<\/p>\n\n\n\n

Outlet-water temperature<\/th>Heating capacity<\/th><\/tr>
35\u00b0C<\/td>6.86 kW<\/td><\/tr>
45\u00b0C<\/td>5.73 kW<\/td><\/tr>
55\u00b0C<\/td>5.41 kW<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

At -25\u00b0C, the published capacity is 5.61 kW at 35\u00b0C water, 4.45 kW at 45\u00b0C, and 3.91 kW at 55\u00b0C.<\/p>\n\n\n\n

This matters when comparing equipment. A project that needs 55\u00b0C water cannot use the 35\u00b0C performance figure simply because it is higher.<\/p>\n\n\n\n

The relationship between leaving-water temperature and system performance is covered in more detail in JNOD’s heat pump flow temperature guide for installers<\/a>.<\/p>\n\n\n\n

COP Is Only Useful With Its Test Conditions<\/h2>\n\n\n\n

COP is often the number buyers notice first, but it is easy to compare it incorrectly.<\/p>\n\n\n\n

The calculation is simple:<\/p>\n\n\n\n

COP = Heating output \u00f7 Electrical power input<\/strong><\/p>\n\n\n\n

The important part is the condition behind the number.<\/p>\n\n\n\n

For the JMU90HC, the published COP at 35\u00b0C outlet water is:<\/p>\n\n\n\n

Outdoor temperature<\/th>COP<\/th><\/tr>
5\u00b0C<\/td>4.70<\/td><\/tr>
-15\u00b0C<\/td>2.33<\/td><\/tr>
-25\u00b0C<\/td>1.72<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

At 55\u00b0C outlet water, COP changes from 3.10 at 5\u00b0C to 1.66 at -15\u00b0C and 1.18 at -25\u00b0C.<\/p>\n\n\n\n

So if two heat pumps show different COP values, check the test conditions before comparing them.<\/p>\n\n\n\n

Use the same: Outdoor temperature + outlet-water temperature + test condition<\/strong><\/p>\n\n\n\n

for both products. A COP measured at 7\u00b0C outdoor temperature and 35\u00b0C water should not be compared directly with a COP measured at -15\u00b0C and 55\u00b0C water.<\/p>\n\n\n\n

For more operating data, see the JNOD JMU90HC R290 top-blow heat pump<\/a>.<\/p>\n\n\n\n

Check the Design Temperature Before Choosing the Model<\/h2>\n\n\n\n

A building does not stay at its design outdoor temperature all winter.<\/p>\n\n\n\n

The design temperature is the condition used to determine how much heating the building needs during colder weather. It varies by location and design method.<\/p>\n\n\n\n

That gives installers a practical way to use a performance table.<\/p>\n\n\n\n

Imagine a project with a calculated heating load of 6 kW at -15\u00b0C. A 9 kW heat pump may look large enough. The next step is to check its published capacity at: -15\u00b0C outdoor temperature<\/strong> and at the water temperature required by the heating system<\/strong>.<\/p>\n\n\n\n

For the JMU90HC, the published capacity at -15\u00b0C is 6.86 kW with 35\u00b0C outlet water, but 5.41 kW with 55\u00b0C outlet water.<\/p>\n\n\n\n

That difference can change the equipment decision.<\/p>\n\n\n\n

PNNL recommends this type of comparison for cold-climate heat pump selection: match the manufacturer’s extended performance data with the building’s design heating load.<\/p>\n\n\n\n

Do Not Confuse the Operating Limit With Heating Capacity<\/h2>\n\n\n\n

This specification is easy to misunderstand.<\/p>\n\n\n\n

If a heat pump is listed as operating down to -25\u00b0C<\/strong>, that tells you the specified operating limit. It does not mean the unit will produce its nominal rated capacity at -25\u00b0C.<\/p>\n\n\n\n

The JMU90HC illustrates the difference. Its published performance extends to -25\u00b0C, but the available heating capacity at that temperature is lower than at 5\u00b0C.<\/p>\n\n\n\n

So when you see:<\/p>\n\n\n\n

\n

Operating range: down to -25\u00b0C<\/strong><\/p>\n<\/blockquote>\n\n\n\n

look for the capacity table as well.<\/p>\n\n\n\n

The operating range tells you whether the unit can operate under that condition. The performance table tells you what output is available.<\/p>\n\n\n\n

JNOD’s cold climate heat pump solutions<\/a> are intended for projects where low outdoor temperatures are an important part of product selection.<\/p>\n\n\n\n

Minimum Capacity Matters Too<\/h2>\n\n\n\n

Cold-climate selection is not only about the coldest day.<\/p>\n\n\n\n

Most of the heating season is normally spent above the design outdoor temperature. An inverter heat pump therefore needs to reduce its output as the building load falls.<\/p>\n\n\n\n

This is where minimum capacity becomes useful.<\/p>\n\n\n\n

A unit that can cover the load on a very cold day may still need to operate at much lower output during milder weather. If the minimum capacity is too high for the application, cycling can become a concern.<\/p>\n\n\n\n

This is why PNNL also recommends considering both maximum and minimum heating capacity when selecting variable-capacity heat pumps.<\/p>\n\n\n\n

For an installer, it is worth checking both sides:<\/p>\n\n\n\n

Can the unit cover the peak load?<\/strong><\/p>\n\n\n\n

Can it turn down enough when the building needs less heat?<\/strong><\/p>\n\n\n\n

How to Read a Performance Table for a Real Project<\/h2>\n\n\n\n

A simple way to work with a performance table is to start with one actual design condition.<\/p>\n\n\n\n

For example:<\/p>\n\n\n\n

Design outdoor temperature:<\/strong> -15\u00b0C
Required outlet-water temperature:<\/strong> 45\u00b0C
Building heating load:<\/strong> 6 kW<\/p>\n\n\n\n

Now check the selected model at those conditions.<\/p>\n\n\n\n

For the JMU90HC, the published heating capacity at -15\u00b0C and 45\u00b0C outlet water is 5.73 kW<\/strong>, with a COP of 1.95<\/strong>.<\/p>\n\n\n\n

That immediately shows that the model does not provide the same output at -15\u00b0C as it does at its nominal rating condition.<\/p>\n\n\n\n

From there, the installer can look at the rest of the system:<\/p>\n\n\n\n