A heat pump for an old house with radiators

A heat pump can also be used in an older house with radiators. What matters, however, is what water temperature the radiators need and how large the heat loss of the house is. This determines whether a low- or high-temperature variant is chosen, or whether changes are recommended.

Why water temperature matters

A heat pump works most efficiently when it heats water to a lower temperature. Older radiators were often designed for a higher temperature from a boiler. The higher the water temperature the house needs, the more work the heat pump has to do.

What we assess

• the heat loss of the house and the condition of the insulation, windows and roof,
• the size and number of radiators in the individual rooms,
• what water temperature the house actually needs in frost,
• the condition of the heating system,
• hot water consumption.

Possible solutions

• a high-temperature heat pump – designed for systems with a higher water temperature; Daikin has one in the Altherma range,
• replacing selected radiators with larger ones, so that a lower water temperature is enough,
• insulation or new windows – reduces the required output,
• gradual steps – insulation first, heat pump afterwards.

What to watch out for

The most common mistake is choosing the output without knowing the heat loss – What heat pump output do I need?. With older houses it is worth spending more time on the design.

A simple test before you decide

If you have a gas boiler, try gradually reducing the heating water temperature on the boiler during a cold period and see whether the house still heats up. If it heats up at a lower temperature, that is a good sign, but it does not replace an accurate design. Note down the outdoor temperature, the set water temperature and which rooms could not keep up. This data is very useful for the design.

When radiators heat unevenly

Cold spots on radiators or a room that stays colder may be related to air or dirt in the system or incorrect balancing. It is therefore worth checking the condition of the system before connecting a new heat source. Heating system flushing may help.

Questions the design should answer

• What water temperature does the house need in the hardest frost?
• Is a low-temperature unit enough, or is a high-temperature one needed?
• Is it worth replacing some radiators?
• Will the heat pump be the main source, or will a backup remain? See A heat pump and a backup heat source: fireplace, boiler or electricity.

Subsidies

When replacing a heat source, subsidies for households may be available – Heat pump subsidy 2026: the new Zelená domácnostiam II.

We will assess your house

Send us information about your house and current heating. We will assess whether a Daikin heat pump is suitable and which variant to choose. For older houses with radiators there is, for example, the Daikin Altherma 3 H HT F. If your radiators do not heat evenly, heating system flushing may also help. Contact us · Daikin heat pumps