Hydraulic Balancing of the Heating System

Setting the presettable thermostatic and riser valves so that each radiator receives exactly the flow rate it needs to deliver its heat output.

How does hydraulic balancing work?

In a heating system, water follows the path of least resistance. Radiators close to the pump and boiler therefore receive too much water, distant radiators too little. To get the last rooms warm as well, flow temperature and pump output are increased – at the expense of efficiency. In hydraulic balancing, the heating load of each room is first calculated and the required flow rate per radiator derived from it. Pre-settable thermostatic valves or balancing valves on the risers are then adjusted so that each radiator receives exactly this amount of water. The result is even heat distribution at a lower flow temperature and lower pump speed. A distinction is made between Method A (approximate, based on radiator size) and Method B (room-by-room heating load calculation), with only Method B realising the full potential.

Which buildings benefit from hydraulic balancing?

Practically all buildings with radiators that have never been balanced or not since a refurbishment – typical signs are flow noise, unevenly heated rooms and a high flow temperature. Requirements are a room-by-room heating load calculation, pre-settable thermostatic valves or riser balancing valves, and a controllable, ideally high-efficiency heating pump. If pre-settable valves are missing, they are retrofitted as part of the measure. Balancing is not useful for pure underfloor heating systems with functioning Tichelmann (reverse return) piping, in which the loops are already of equal length. In Germany, balancing has been mandatory since 2024 for certain refurbishments and larger buildings; in Austria it is recommended and a prerequisite for many follow-on measures such as heat pumps or condensing boiler optimisation.

What does hydraulic balancing actually deliver?

Heating energy falls by 5 to 15 %, at the upper end for old systems that have never been adjusted. An apartment building with a space heating demand of 70,000 kWh saves around 6,600 kWh of natural gas and about 1.3 t of CO2 per year. In addition, the flow temperature can usually be lowered by 5 to 10 K after balancing. Costs are 600 to 1,200 € for a detached house and 100 to 200 € per dwelling in an apartment building. Over a 15-year service life, the measure pays back in 2 to 5 years.

Energy carrier

Erdgas, Heizöl, Pellet, Strom → Erdgas, Heizöl, Pellet, Strom

Savings potential

5-15 %

Worked example

An apartment building with 700 m² of usable floor area has a space heating demand of 70,000 kWh per year, met by a gas boiler with an efficiency of 0.85. The system has never been hydraulically balanced: the ground-floor flats are overheated, while the top-floor flats only get warm enough at a high flow temperature. After a room-by-room heating load calculation, the pre-settable thermostatic valves are set to the calculated flow rates and the pump is set to a lower head. A saving factor of 0.08, i.e. 8 % of the space heating demand, is assumed for such a system. The final energy saving is 70,000 × 0.08 / 0.85 = 6,588 kWh of natural gas per year. With an emission factor of 0.201 kg CO2/kWh, this corresponds to about 1.3 t of CO2 annually. At a cost of 100 to 200 € per dwelling, balancing pays back in 2 to 5 years.

Investment & payback

EFH: 600-1.200 €; MFH ca. 100-200 €/Wohneinheit · Service life: 15 a · Payback: 2-5 a

Applicability

Requirements

Exclusion criteria

Typical buildings

Frequently asked questions

How much does hydraulic balancing cost?

Hydraulic balancing costs 600 to 1,200 € for a detached house and about 100 to 200 € per dwelling in an apartment building. The price depends on whether a room-by-room heating load calculation is carried out and whether pre-settable thermostatic valves need to be retrofitted. With savings of 5 to 15 % of heating energy, the measure pays back in 2 to 5 years, with an effective life of around 15 years.

Is hydraulic balancing mandatory in Austria?

In Austria, hydraulic balancing is not legally required, but it is recommended and is a prerequisite or component of many subsidy programmes for boiler replacement. In Germany, it has been mandatory since 2024 under the Building Energy Act (GEG) for new heating systems and in larger residential buildings with gas heating. The calculation is based on the heating load standard DIN EN 12831 as well as ÖNORM H 7500 and VDI 3805.

How long does hydraulic balancing take?

Hydraulic balancing in a detached house with 8 to 12 radiators takes about half a day to a full working day. The larger part is spent on the heating load calculation and planning; setting the valves themselves is quick. In an apartment building, several days should be allowed, as all flats must be accessible. If valves need to be replaced, the duration increases accordingly.

What is the difference between Method A and Method B in hydraulic balancing?

In Method A, the flow rate is estimated approximately from radiator size and building type. In Method B, the heating load of each room is calculated individually according to DIN EN 12831 and the exact flow rate per radiator derived from it. Method B is more laborious but delivers considerably more accurate results and allows a greater reduction in flow temperature. Method B is usually required for heat pumps and subsidies.

Do you need new thermostatic valves for hydraulic balancing?

New thermostatic valves are only needed if the existing ones are not pre-settable. Pre-settable valves have a scale on the valve body that can be used to limit the maximum flow. Older valves without this function must be replaced, which costs 20 to 40 € per valve body plus installation. Alternatively, in apartment buildings, balancing valves can be fitted in the risers.

Related measures

Standards & sources

Metering points in the EDM Toolbox

Vor/Nach-Vergleich via Wärmemengenzähler im Heizkreislauf zeigt Erfolg sofort. EDM-Dashboard kann VL/RL-Temperaturen, Pumpenstrom und Witterung kombinieren - typische Erfolgskennzahl: VL kann nach Abgleich um 5-10 K abgesenkt werden.

All measures