One of the most common concerns for homeowners upgrading to a heat pump is whether their existing radiators can remain in use. The good news? In many cases, yes—you can. However, it depends on your radiator size, system design, and the type of heat pump being installed.

This article will explain the key considerations and best practices when integrating air to water heat pumps with existing radiators.

✅ Why Radiator Compatibility Matters

Heat pumps—especially air to water systems—work best at lower flow temperatures (typically 35–55°C), compared to traditional gas or oil boilers (which operate at 70–80°C). Because of this, the ability of your radiators to deliver sufficient heat at these lower temperatures is crucial for overall efficiency and comfort.

Key Questions to Ask

1. Are My Radiators Big Enough?

Standard radiators installed for boiler systems may not be large enough to effectively heat rooms with lower temperature water from a heat pump. Undersized radiators can lead to:

• Slower heating times

• Reduced efficiency

• Cold spots

You may need to upsize certain radiators or add additional units in larger rooms.

2. What Type of Radiators Do I Have?

• Single panel radiators may struggle with heat output in low-flow systems.

• Double panel or column radiators perform better and are often compatible.

• Fan-assisted radiators (also called low-temperature radiators) are specifically designed for use with heat pumps.

3. Is My Home Well Insulated?

A well-insulated home loses less heat, making it easier for low-temperature radiators to maintain comfort. If your insulation is poor, radiators will need to work harder—possibly requiring upgrades.

What Are Your Options?

✔️ Use As-Is (If Compatible)

If your current radiators are sufficiently sized and your rooms are well-insulated, you may be able to use them without any changes.

Replace Select Radiators

Many heat pump retrofit projects involve replacing only a few key radiators—typically in the largest or coldest rooms.

➕ Add Supplementary Heating

In some cases, underfloor heating or a hybrid setup (with additional heat sources) may complement your existing radiators for a balanced system.

System Design Considerations

When adapting radiators for a heat pump:

• Heat loss calculations are essential to ensure each room gets enough heat.

• Install thermostatic radiator valves (TRVs) to fine-tune temperature control.

• Consider a buffer tank to improve system stability and reduce cycling.

Your HVAC installer will help size the radiators to your new low-temperature heating profile.

Pro Tip: Pre-Commissioning Test

Before installation, ask for a radiator survey. This test evaluates your current emitters under heat pump conditions, revealing which radiators need to be replaced or retained.

Benefits of Using Existing Radiators

• Lower upfront cost (vs. full underfloor installation)

• Faster installation timeline

• Minimal disruption to flooring or walls

• Compatible with retrofit-friendly air to water heat pumps

❗ When You Should Upgrade Radiators

• Rooms remain cold even after system balancing

• You plan to lower flow temperatures further to maximize efficiency

• Your radiators are old, corroded, or poorly maintained

• You want better comfort and modern aesthetics

Final Verdict

Yes, you can often use your existing radiators with an air to water heat pump—but some may need resizing or upgrading. A professional system assessment and radiator heat output calculation are critical to making the most of your investment.

Combining heat pump technology with an optimized radiator system can deliver low-carbon, energy-efficient heating that keeps your home warm all winter long.