Hydraulic balancing for heat pumps: What you should know

You are planning to switch to a heat pump or may have already installed one. In the documents from the heating contractor, one point quickly gets overlooked: hydraulic balancing. It sounds technical, and it is. But above all, it is crucial for what you expect from your heat pump: low operating costs, quiet operation, and reliably warm rooms.

Anyone who researches online quickly comes across contradictory statements. Sometimes balancing is mandatory, sometimes supposedly unnecessary. And it is often said that it is not possible at all with underfloor heating. No wonder this creates uncertainty.

A look at reality shows: Without functioning hydraulic balancing, a heat pump cannot work with maximum efficiency. The best heat pump settings are no use if the heating water circulates but does not arrive where it is needed.

Especially at low flow temperatures, as are common with modern heat pumps, hydraulic balancing is crucial. Only when the water volumes are distributed correctly and evenly does the system work efficiently.

If this fine-tuning is missing, the heat pump works with increased effort, switches on and off more frequently, consumes more electricity as a result, and breaks down faster. At the same time, distant rooms often remain undersupplied. This is not only unpleasant, but also costs real money in the long run.

In this article, you will learn why hydraulic balancing for heat pumps is so important, how it works, and what you can specifically do about it.

Even warmth throughout the house – that is what hydraulic balancing is all about

When you turn up a heating thermostat, you expect it to get warm. Exactly where you want it. But this only works everywhere in every room if the heating system is properly adjusted in the background. That is exactly what hydraulic balancing is about.

The principle behind it is simple: Radiators or underfloor heating should receive exactly the amount of water they need – no more, but also no less. Without this coordination, the heating water always takes the path of least resistance, and that initially means the radiators closest to the boiler room. More distant rooms, on the other hand, receive less heating water and therefore also less heat.

So that the distant rooms still get sufficiently warm, the flow temperature is often turned up. However, a higher flow temperature also means that the heat pump has to provide higher temperatures, which reduces its efficiency. This is directly noticeable on the electricity bill.

At the same time, relatively high temperatures return from the other radiators, causing the heat pump to cycle more frequently. This increases the strain on the heat pump and reduces its service life.

A correctly performed hydraulic balancing of the heating system prevents all of this. The system works evenly with low temperatures. Every room still becomes reliably warm, even at low outdoor temperatures. This means the system not only runs more efficiently, but also noticeably more quietly.

Therefore, the rule is: Hydraulically balance the heating system in order to operate the heat pump efficiently. This is not an optional finishing touch, but a central component for the efficiency of the heat pump and the comfort of the residents.

Is hydraulic balancing mandatory for heat pumps?

Hydraulic balancing has been mandatory for more than 50 years. Nevertheless, in the past it was only rarely carried out. Yet the simplest variant of hydraulic balancing is so simple that you can even do it yourself without a specialist company.

For an existing system, it is basically sufficient to set the valves by rule of thumb. This works via presettable heating valves, which are hidden under the thermostats. You will find them when you unscrew the thermostat heads.

The presettable heating valves usually have setting values from 1 to 6 or 1 to 9. The higher the value, the greater the possible flow rate. A good rule of thumb is to set the three radiators with the shortest distance to the boiler room to 3.

Leave the three radiators that are farthest away from the boiler room set to the maximum value for the time being. Set all remaining radiator valves to a value roughly in the middle, between 3 and the maximum value. With this method, you can already achieve a good result without much effort.

If you want to do it a little more precisely, then procedure A for hydraulic balancing is a good option. Procedure A is somewhat more accurate than the rule-of-thumb method mentioned above, but it still works in a fairly general way.

Standard values are used, per radiator or room. Compared with the very precise procedure B, this saves a lot of effort. With this method, systems can already be balanced accurately enough for trouble-free operation.

Subsidy only with proof: Why procedure B matters

However, if you want to apply for a subsidy from BAFA for the installation of a heat pump system, you must provide proof of hydraulic balancing for your system. Balancing is therefore a mandatory technical requirement.

The subsidy is only available if the system has been balanced and the specialist company formally confirms the balancing. Here, BAFA requires what is known as procedure B. In this process, the heating load must first be calculated for each room and the exact flow rate determined. The respective setting values for the heating thermostats then result from this calculation.

But balancing is worthwhile even without a subsidy. It reduces energy demand, improves heat distribution, and extends the service life of the system. An investment pays off over the years, especially with heat pump systems, through lower operating costs and greater comfort.

What hydraulic balancing costs depends on the condition of the system, but you will learn more about that later.

Calculate the room-by-room heating load: This is where you lay the foundation!

Before you set the flow in the heating system, you need to know how much heat each room actually needs. That is exactly what the heating load calculation provides. It forms the basis for heat balancing throughout the entire building and is therefore an indispensable first step on the way to a functioning heat pump system.

Heating load and heating output are often confused. The heating load describes the heat demand of a room, depending on the insulation standard, window area, and location in the house. The heating output, on the other hand, is what the radiators emit into the room or what your heat generator, i.e. the heat pump, delivers to the house. In order for all rooms to become evenly warm, heating load and heating output must match each other, meaning they should be roughly the same size.

Often the heating load is not calculated, but only estimated. But the rules of thumb for estimating have two major disadvantages:

First, the heating output is usually set too generously. This leads to an oversized heat pump. Oversizing is poison for a heat pump, however. As a result, it starts cycling more often, requires more electricity, and risks breaking down faster.

Second, every room is treated the same, even though a north-facing corner room with two exterior walls has completely different requirements than a well-protected room in the middle of the house. The more accurately the heating load is determined, the more precisely you can set your system.

The heating load calculation is carried out on the basis of the so-called standard outdoor temperature. This is the lowest outdoor temperature that can statistically be expected at your place of residence.

For me in southern Hesse, this value is minus ten degrees, for example. In some regions, however, it can get significantly colder. In Oberwiesenthal in the Ore Mountains, the standard outdoor temperature is even minus sixteen degrees. These sometimes significant differences are therefore also taken into account in the room-by-room heating load calculation.

Check the heating load calculation with a sense of proportion

The calculation not only shows you how much output your heat pump system must deliver in total, but also which radiators are suitable and which may still need to be adapted. Anyone who works carefully here lays the foundation for a quiet, efficient, and long-lasting system.

Tip: Sometimes even the heating load calculation delivers values for the heating output for the heat pump output that are too high. This is because the calculation takes into account many safety factors that are not required for heat pumps.

You can determine this by at least checking the heating load on the basis of heating energy consumption. If the heating load based on consumption is significantly lower than the heating load calculation, you should correct the heat pump output downward accordingly. In the heat pump knowledge portal, you can test the heating load based on heating energy consumption.

Check heating load and heating surfaces – this is how the next step works

Once the heating load has been determined for each room, the next question arises: Is the existing heating surface sufficient to cover this demand? Or are new radiators with a larger surface area and higher output needed, or is there even another solution?

Whether the installed heating element is sufficient depends on three factors. The type, its size, and the required flow temperature are relevant. The last point is particularly important, because the heat pump works most efficiently at low flow temperatures. If a radiator can manage with a maximum of 50 to 55 degrees, then it is perfectly suitable for operation with modern heating technology, such as the heat pump.

In older buildings, this can sometimes become tight. Old sectional radiators often have too little surface area and are designed for higher temperatures. In these cases, it is sometimes enough simply to install a modern radiator that can emit more output with the same size.

Sometimes that alone is not enough, however. Then it is worth looking at modern low-temperature radiators. These models transfer significantly more heat at a lower flow temperature. They achieve this, for example, through larger internal heat exchanger surfaces, the use of extremely heat-conductive aluminum as a material, or the use of small fans, known as activators.

Whether replacement is worthwhile also depends on the year of construction. In houses from around 1995 onward, panel radiators were often already installed that are suitable for lower temperatures.

In addition, the thermal insulation in these buildings is often so good that the existing radiators harmonize with the new heat pump. And that is without elaborate measures. Nevertheless, all radiators should also be checked in these houses, because just one element that is too small leads to higher flow temperatures and can thus slow down the entire system.

If the radiator is not enough: Surface heating as an alternative

If replacing individual radiators is not an option or you are renovating more extensively anyway, surface heating may also be considered. A heat pump with underfloor heating works particularly efficiently because the large surface area manages with a particularly low flow temperature. This increases efficiency and reduces operating costs.

However, retrofitting is only possible with considerable effort. The most cost-effective option for retrofitting is possible by milling the heating pipes into the existing screed. This preserves the floor structure, and the intervention in the building fabric remains comparatively limited.

In this case, the existing insulation is important. If there is no sufficient insulation layer under the screed, at least the basement ceiling toward the unheated basement should be insulated afterwards. Otherwise, a significant portion of the heat disappears into the basement, and that would be wasted money.

Whether radiator replacement or underfloor heating: The goal is for the heating surfaces to deliver the necessary output without the heat pump having to work excessively. Only when the interaction between heating load and heating surfaces is right are the foundations laid for an optimally functioning system.

Then not only the water volumes are correct, but also the entire interaction between heating load, flow temperature, and heat emission. A buffer storage tank can help reduce cycling, especially in systems with a low water volume.

6 common mistakes in hydraulic balancing and how to avoid them

Hydraulic balancing is not rocket science, but it should be well prepared. These six mistakes occur particularly often in practice and can be easily avoided with the right approach:

1. Estimation instead of calculation: Anyone who relies on general values saves in the wrong place. Without the room-by-room heating load calculation, the balancing remains inaccurate. The result: incorrect settings and unnecessary energy consumption.
2. Heat pump output too high: If the heat pump’s heating output is too large, it will cycle frequently, which shortens its service life. Checking the heating load based on actual heating energy consumption helps here. You can check the heating load here.
3. Radiators incorrectly sized: Radiators that are too small or unsuitable slow down the whole system. Especially with heat pumps that work with low flow temperatures, the heating surface must be right.
4. No valve presetting: Only once the presettings on the thermostatic valves have been made according to the hydraulic balancing does the system run perfectly. The water volumes must be set precisely – room by room.
5. Flow temperature too high: A poorly adjusted system runs at an unnecessarily high temperature. This lowers efficiency and increases electricity costs. Anyone who wants to hydraulically set the heat pump must also keep an eye on the heating surfaces.
6. Specialist company missing or wrong service provider: Not every installer takes the time to fully adjust the system. If the heat pump is to be subsidized, the hydraulic balancing must not be done by yourself. This is only possible with professional support from a specialist company.

What does hydraulic balancing cost and where can you save?

The costs for hydraulic balancing depend heavily on the condition of the heating system. In a typical single-family house with standard radiators and existing thermostatic valves, they are usually between 300 and 900 euros (as of May 2025). The decisive factor is whether a room-by-room heating load calculation including radiator check is already available and whether valves or radiators need to be adapted.

If additional work is added, such as replacing a radiator or converting to presettable valves, the costs rise accordingly. With surface heating, it can also become more complex and therefore more expensive.

However, support is available. The Federal Office for Economic Affairs and Export Control BAFA subsidizes heating optimization with grants. Anyone who installs a new heat pump receives the subsidy only if the flow rates have been professionally set and documented. Funding is also possible for existing systems, provided the balancing is carried out and documented professionally.

Done properly, balancing saves significantly more over the years than it costs. Lower electricity consumption, a longer service life for the technology, and more everyday comfort – these are the benefits.

By the way: Anyone who also generates hot water with the heat pump can of course do so.

What happens if you do without balancing?

A functioning heating system is not a luxury, but a technical necessity. If the correct setting of the water volumes is missing, this has direct consequences:

• Uneven heat distribution: Without regulated flow, some radiators receive too much heat, others too little. This leads to oversupply in individual rooms, while elsewhere it cannot get warm enough.
• Higher electricity consumption due to frequent cycling: If a heat pump constantly starts up and switches off again, electricity consumption rises. This so-called cycling often occurs when the system is not hydraulically balanced. A buffer storage tank can additionally help reduce cycling. It absorbs excess heat and releases it evenly. This makes the system run more quietly and efficiently.
• Shorter service life of the heat pump: Frequent cycling increases wear on the heat pump. This shortens the service life of the technology and therefore increases maintenance costs.
• Lost subsidies: Without proof of hydraulic balancing of the heating system, there is no subsidy. Anyone who saves here gives away money and ends up paying extra.

Conclusion: Good planning saves money and ensures warm feet

Hydraulic balancing is more than a checkmark on the checklist. It ensures that your heat pump runs perfectly, the rooms become evenly warm, and electricity consumption stays within reasonable limits. Especially at low flow temperatures, as are typical for heat pumps, balancing determines comfort and cost-effectiveness.

Do not rely on rough estimates. Only a proper calculation shows whether radiators, valves, and pipework fit together. The settings of a heat pump only produce the desired effect when the system as a whole is coordinated.

Whether you are building new or modernizing an existing system: Without balancing, you waste energy and risk losing subsidies. An investment in planning and setting the heat transfer system pays off. Anyone who works properly now will have less stress later, lower operating costs, and greater living comfort.

If you want to take the next step, speak with a specialist company or get advice from a qualified energy consultant. The hydraulic balancing must be carried out according to a recognized procedure and documented in writing; otherwise, it is considered not completed for the BAFA subsidy.

Not every installer automatically includes balancing. Therefore, check the offer and, if necessary, ask specifically about it before you sign the offer. Many people also obtain independent advice beforehand to check whether the existing system is suitable for a heat pump at all.

You can get an initial assessment directly with our free heat pump check. With just a few details, you can find out whether your house is generally suitable for a heat pump.

Image sources:

1. Featured image: (Photo: Adobe Stock)
2. Presettable radiator valve (Photo: Carsten Herbert)
3. Removed heating thermostat – the adjustable valve is located underneath (Photo: Carsten Herbert)
4. Calculate heating load and realistically assess costs (Photo: Canva / used license-free with rights for commercial use)
5. Ribbed radiator in an older building (Photo: Carsten Herbert)
6. Very old radiator – setting via valve without thermostat (Photo: Carsten Herbert)
7. Specialist adjusts heating pipes in the basement (Photo: Canva / used license-free with rights for commercial use)