As homeowners and builders move toward sustainable heating solutions, pairing a heat pump with existing or new radiator systems has become an increasingly popular and practical choice. But how do you ensure proper compatibility and performance when integrating a heat pump with radiators?

In this comprehensive guide, we explain how heat pumps work with radiators, key installation considerations, and step-by-step instructions for connecting the two systems efficiently.

Can You Use a Heat Pump with Radiators?

Yes — air-to-water heat pumps (and ground-source heat pumps) can work with radiators, but with some important conditions:

• Low-temperature radiators or oversized conventional radiators are ideal.

• The system must be designed or adapted for lower flow temperatures (typically 35°C–55°C).

• Proper integration ensures energy efficiency, comfort, and long-term reliability.

How Heat Pumps Work with Radiators

Unlike traditional boilers that supply water at high temperatures (70°C–80°C), heat pumps operate more efficiently at lower flow temperatures. This means the heat emitted from radiators may feel less intense, but the overall comfort is maintained through:

• Continuous, gentle heating

• Larger heat-emitting surfaces (e.g., bigger radiators or underfloor heating)

• Well-insulated homes that retain warmth effectively

To optimize this setup, it's essential to design the radiator circuit and flow rates specifically for heat pump compatibility.

Types of Radiators Suitable for Heat Pumps

If upgrading from a gas boiler, an installer may recommend replacing or resizing key radiators to achieve the desired heat output.

Step-by-Step: How to Connect a Heat Pump to Radiators

Step 1: Assess Building Heat Loss

A certified technician performs a room-by-room heat loss calculation to determine the required radiator output at lower temperatures.

Step 2: Select or Resize Radiators

Choose radiators based on the flow temperature your heat pump will deliver (usually 35°C–55°C). Use manufacturer heat output charts to match the right size.

Step 3: Install the Heat Pump

Install the air-to-water heat pump outdoors and connect it to a buffer tank or thermal store if needed. Ensure proper hydraulic separation and anti-vibration mounts.

Step 4: Design the Pipework and Hydraulics

• Use suitably sized piping to maintain flow rates

• Incorporate a mixing valve or weather compensation controller

• Consider using a buffer tank to reduce cycling and manage flow control

Step 5: Connect to the Radiator Circuit

• Connect the flow and return lines to the radiator distribution system

• Bleed the radiators and check for leaks

• Set system pressures appropriately

Step 6: Configure Controls and Thermostats

Install a smart or programmable thermostat that supports heat pump modulation and weather compensation.

Step 7: Commission the System

Run diagnostics, adjust flow rates, check delta T across radiators, and fine-tune control parameters.

Additional Tips for Efficient Operation

• Lower the flow temperature as much as possible without sacrificing comfort

• Use thermostatic radiator valves (TRVs) to balance room temperatures

• Insulate pipework to minimize heat loss

• Schedule regular maintenance for optimal performance and system longevity

Benefits of Connecting Heat Pumps to Radiators

• ✅ Energy-efficient heating, especially in well-insulated homes

• ✅ Reduced carbon emissions compared to fossil-fuel boilers

• ✅ Eligible for government incentives in many countries

• ✅ Can utilize existing radiator infrastructure with proper upgrades

Potential Challenges

Conclusion

Connecting a heat pump to a radiator system is a smart way to modernize your home's heating with minimal disruption — but it must be done correctly. From accurate sizing to smart controls, every detail matters for efficiency, comfort, and system longevity.

If you're retrofitting or building a new home, work with an experienced installer to design the perfect heat pump + radiator system for your needs.