Upgrading existing systems for heat pump compatibility across South West England
Switching to a heat pump is one of the most effective steps you can take to reduce your home's carbon footprint and energy bills. But for many homes, the existing central heating system needs upgrading before a heat pump can operate at its best.
At Devon Heat Pumps, we specialise in preparing homes for heat pump technology — assessing, redesigning and upgrading your heating distribution system so your new heat pump delivers maximum efficiency from day one. We handle everything from individual radiator upgrades through to complete system redesigns, working around you to minimise disruption throughout.
Traditional gas and oil boilers run at high flow temperatures — typically 70–80°C. Radiators and pipework in most UK homes were sized on the assumption that water this hot would be circulating through them. Heat pumps work differently.
A heat pump is most efficient when operating at lower flow temperatures, typically 35–55°C. At these lower temperatures, a standard-sized radiator simply cannot emit enough heat to warm the room effectively. The result without upgrading: the heat pump has to work harder, efficiency drops, and running costs rise.
Old System
High flow temps (70–80°C), undersized radiators, no zoning — inefficient with a heat pump
Retrofitted System
Low flow temps (35–55°C), correctly sized emitters, smart zoning — heat pump runs at peak COP
A central heating retrofit isn't a one-size-fits-all job. Every home is assessed on its own merits. Depending on your property and existing system, work may include any combination of the following:
Replacing undersized radiators with larger double-panel units, or adding fan-assisted convectors where space is limited — ensuring adequate heat output at low flow temperatures.
Upgrading or reconfiguring pipework where necessary to suit the heat pump's flow rates, including flushing and chemical treatment of the existing system.
Installing buffer vessels or unvented hot water cylinders compatible with heat pump operation, ensuring stable system pressure and reliable domestic hot water at the correct temperature.
Fitting smart thermostats, weather compensation controls and zone valves so your heat pump operates intelligently — reducing energy use and improving comfort in every room.
Getting the radiator specification right is critical. Because heat pumps deliver water at lower temperatures than a boiler, each radiator needs to be sized for the actual flow temperature the heat pump will use — not the 70°C assumption baked into most standard sizing tables.
As a rough guide, a radiator that would achieve its rated output at 70°C will produce significantly less heat at 45°C. We use room-by-room heat loss calculations to determine the exact output needed in every space, then specify radiators accordingly.
Large double or triple-panel steel radiators
The most common upgrade — larger surface area compensates for lower water temperature.
Fan-assisted radiators (fan convectors)
Ideal where space is constrained — a built-in fan boosts output even at low flow temperatures, allowing a smaller unit to do the job.
Underfloor heating (new areas)
Where practical, UFH is the ideal low-temperature emitter and pairs perfectly with heat pumps. We can combine UFH in new areas with upgraded radiators elsewhere.
We don't guess — we calculate. Before specifying a single radiator or recommending any works, we carry out a full heat loss assessment of your property. This tells us exactly how much heat each room needs to stay comfortable on the coldest winter days, which in turn drives every sizing decision we make.
Our system design process covers:
This rigorous approach is what separates a well-performing heat pump installation from one that underdelivers. We provide a full system design document as part of our MCS-compliant installation process.
Not everything needs replacing. One of the first things we do is a thorough survey of your existing heating system — identifying what's already fit for purpose and what genuinely needs upgrading. We approach every retrofit with the goal of minimising cost and disruption while still achieving the system performance your heat pump requires.
In many homes, a significant portion of the existing pipework and some radiators can be retained. We'll be upfront about what we find and give you a clear, itemised picture of what work is needed and why.
Survey First
We assess your existing system in detail before recommending any works, so there are no surprises.
Keep What Works
We only recommend replacing components that genuinely limit system performance — reducing cost and waste.
Phased Works
Where budget is a consideration, we can plan work in phases — prioritising the rooms that will benefit most first.
Minimal Disruption
Our experienced installers work efficiently and tidily, keeping your home comfortable throughout the process.
Ready to find out what's involved in retrofitting your home? Get in touch for a free, no-obligation survey and quote.
Request a QuoteGet in touch for a free, no-obligation survey. We'll assess your existing system, run the heat loss calculations and give you a clear quote for the works needed.