A high temperature heat pump is an air source heat pump that can heat the water in your radiators to around 65°C to 80°C, close to what a traditional gas or oil boiler produces. Standard heat pumps usually work best at much lower temperatures, around 35°C to 55°C, which is why some older homes need bigger radiators or extra insulation before they can switch.
A high temperature model reduces or sometimes removes that need, making low carbon heating far easier for period properties, larger homes and houses with older radiators.
At Guscott Heating, we install air source heat pumps for homeowners and landlords right across Kent and the South East.
In this guide, we explain how high temperature heat pumps work, what they cost to buy and run, their pros and cons, and the types of property they suit best.
What Is a High Temperature Heat Pump and Who Is It For?
A high temperature heat pump is a renewable heating system that works like a standard air source heat pump but can deliver much hotter water to your radiators, and it is mainly for homes where a standard heat pump would struggle without major upgrades. It sits outside your home, takes free heat from the outdoor air and uses electricity to boost that heat to a temperature your existing radiators can use.
This matters a great deal in the UK. Around one in five homes in England was built before 1919, according to the English Housing Survey, and Kent has a large share of older housing, from Georgian townhouses in Faversham to Victorian villas in Sevenoaks and Edwardian semis across Medway.
Many of these homes have solid walls, single glazing in places and radiators sized for a hot boiler. A high temperature heat pump gives them a realistic route away from gas, oil and LPG.
You may also hear them called high temperature air source heat pumps, high flow temperature heat pumps or simply boiler replacement heat pumps.
Is your home suited to a high temperature heat pump? Guscott Heating provides air source heat pump installation across Kent and the wider South East of England. We will carry out a full room by room heat loss survey and tell you honestly whether a standard or high temperature model is the better choice for your home. Get in touch today for a free estimate tailored to your location.
How Does a High Temperature Heat Pump Work?
A high temperature heat pump works by collecting warmth from the outside air, squeezing it to raise its temperature, and passing that heat into the water that flows round your radiators and hot water cylinder. It is the same basic process as a fridge, only in reverse, and it keeps working even on cold winter days in Ashford or Maidstone.
In simple terms, it happens in four steps:
- A refrigerant, a special fluid inside the heat pump, soaks up heat from the outdoor air and turns into a gas.
- A compressor squeezes the gas, which makes it much hotter.
- The hot gas passes its heat into your heating water.
- The refrigerant cools, turns back into a liquid and starts the cycle again.
What Lets It Reach Higher Temperatures
Standard and high temperature heat pumps share the same basic design. The difference lies in the parts that allow a high temperature model to push water much hotter:
- Better refrigerants. Many modern high temperature units use R290, a natural refrigerant better known as propane. It handles high temperatures well and has a very low impact on the climate compared with older refrigerants. Some specialist models use carbon dioxide (R744).
- More capable compressors. Upgraded compressors and clever refrigerant circuits help the unit keep working hard in cold weather.
- Two stage systems. Some high temperature heat pumps use two refrigerant circuits, one feeding the next, to reach temperatures of 80°C or more. These are often called cascade heat pumps.
Well known examples include the Vaillant aroTHERM plus, the Daikin Altherma 3 H HT and the Mitsubishi Electric Ecodan R290 range, which can produce water at around 70°C to 75°C depending on the model and conditions.
Why It Does Not Run Hot All the Time
A high temperature heat pump does not run at full temperature all year. A setting called weather compensation automatically lowers the water temperature on milder days and only raises it when it is genuinely cold. Kent is one of the mildest parts of the UK, so for much of the heating season your system can run cooler and more efficiently, saving the hottest temperatures for the coldest spells.
What Are the Pros and Cons of a High Temperature Heat Pump?
The pros and cons of a high temperature heat pump balance easier installation and boiler like warmth against slightly higher running and upfront costs. Here is a side by side view.
| Pros | Cons |
| Works with existing radiators: Most homes can keep their current radiators and pipework, avoiding lifted floorboards and redecorating. | Lower efficiency at high temperatures: Running at 70°C uses noticeably more electricity than running at 45°C. |
| Familiar warmth: Radiators get as hot as they would with a gas boiler, so rooms heat up the way you are used to. | Higher upfront cost: The units are more complex, so they usually cost more than a standard heat pump. |
| A route off fossil fuels for older homes: Homes unsuited to standard heat pumps can still switch and cut carbon emissions. | Running costs can exceed gas: This is most likely on a standard electricity tariff rather than a heat pump tariff. |
| Protects period character: It is ideal for listed buildings and conservation areas where radiator or insulation changes are restricted. | Still needs insulation: Loft insulation and draught proofing still lower bills and help the system run cooler. |
| Grant eligible: It qualifies for the £7,500 Boiler Upgrade Scheme grant. | Relies on expert design: A poorly set up system can be expensive to run. |
How Does a High Temperature Heat Pump Compare With a Standard Heat Pump?
A high temperature heat pump compares with a standard heat pump as the easier option to fit in older homes, while a standard heat pump is usually cheaper to run in homes that can take it. The trade off is simple: higher water temperatures mean fewer changes to your home but slightly lower efficiency.
| Feature | Standard air source heat pump | High temperature heat pump |
| Typical water temperature | 35°C to 55°C | 65°C to 80°C |
| Typical efficiency (SCOP) | Around 3 to 4 | Around 2.5 to 3.2 |
| Radiator upgrades | Often needed in older homes | Often fewer or none needed |
| Insulation upgrades | Usually recommended | Still helpful, but less critical |
| Typical installed cost before grant | £8,000 to £15,000 | £10,000 to £18,000 |
| Boiler Upgrade Scheme grant | £7,500 | £7,500 |
| Best suited to | Modern or well insulated homes | Period, larger and harder to insulate homes |
SCOP stands for seasonal coefficient of performance. A SCOP of 3 means you get roughly three units of heat for every one unit of electricity you pay for, averaged over a year.
It is worth knowing that a well designed standard heat pump with a few upgraded radiators can often heat an older home perfectly well. A high temperature model is the right answer when those upgrades would be too costly, too disruptive or simply not possible, which is why a proper survey matters.
How Much Does a High Temperature Heat Pump Cost to Install?
A high temperature heat pump typically costs around £10,000 to £18,000 to install before any grant, and roughly £2,500 to £10,500 once the £7,500 Boiler Upgrade Scheme grant is taken off. The unit itself usually costs a little more than a standard model, but you may save money elsewhere because fewer radiators need replacing.
| Property type | Typical cost before grant | Typical cost after £7,500 grant |
| Two to three bedroom period terrace or semi | £10,000 to £13,000 | £2,500 to £5,500 |
| Three to four bedroom detached home | £12,000 to £15,000 | £4,500 to £7,500 |
| Large or rural home with high heat demand | £14,000 to £18,000+ | £6,500 to £10,500+ |
These are typical ranges and are a guide only. Your price depends on the size of your home, how much heat it loses, whether you need a new hot water cylinder and how easy the installation is.
What Affects the Price
- Heat demand. Bigger or draughtier homes need a larger, more powerful unit.
- Hot water cylinder. Homes moving from a combi boiler will need a cylinder.
- Radiators and pipework. Even high temperature systems sometimes need one or two radiators upgrading.
- Electrics and controls. Some homes need electrical upgrades or new smart controls.
- Location of the outdoor unit. Longer pipe runs and tricky access add time and cost.
Grants and Financial Support
High temperature heat pumps qualify for the same support as standard air source heat pumps:
- Boiler Upgrade Scheme: £7,500 off the cost in England and Wales, claimed for you by your MCS certified installer. You must own the property, and the heat pump must replace a fossil fuel or direct electric heating system.
- 0% VAT: Heat pumps and their installation are currently charged at 0% VAT in Great Britain until at least March 2027.
- Local support. Lower income households may qualify for help through council run schemes such as the Warm Homes: Local Grant. Check with your district council, whether that is Swale, Thanet, Dover or elsewhere in Kent.
How Much Does a High Temperature Heat Pump Cost to Run?
A high temperature heat pump costs slightly more to run than a standard heat pump, but on a smart tariff it can be cheaper than oil or LPG and close to the cost of gas. The higher the water temperature, the more electricity the heat pump uses, so running costs depend heavily on how well the system is designed and how cool it can run for most of the year.
The table below shows rough yearly heating and hot water costs for a typical older Kent home needing around 14,000 kWh of heat a year. It assumes electricity at around 26p per kWh, a heat pump tariff averaging around 15p per kWh, gas at around 6.5p per kWh, heating oil at around 6.5p per kWh and LPG at around 8p per kWh. These are illustrative figures only, as energy prices change regularly.
| Heating system | Assumed efficiency | Approx. cost, standard tariff | Approx. cost, heat pump tariff |
| Standard heat pump with radiator upgrades | SCOP 3.4 | £1,070 | £620 |
| High temperature heat pump | SCOP 2.8 | £1,300 | £750 |
| Modern gas boiler | 88% | £1,035 | Not applicable |
| Oil boiler | 85% | £1,070 | Not applicable |
| LPG boiler | 88% | £1,270 | Not applicable |
On top of these figures, gas, oil and LPG users also pay for standing charges, tank rental or boiler servicing, while a full switch to a heat pump means you can drop the gas standing charge altogether, worth roughly £100 to £120 a year.
The key takeaway is that the biggest savings come from replacing oil and LPG, which is especially relevant for rural, off gas homes across the Kent Weald and Romney Marsh, around villages near Cranbrook (TN17), Headcorn (TN27) and New Romney (TN28).
Which Properties Are Best Suited to a High Temperature Heat Pump?
The properties best suited to a high temperature heat pump are period homes, solid wall houses, listed and conservation area properties, large homes with high heat demand and off gas rural homes with older radiators. In these homes, a standard heat pump would often need costly or disruptive work first.
Victorian, Edwardian and Georgian Homes
Older homes with solid brick walls lose heat faster than modern cavity wall houses and often have radiators sized for a hot boiler. They are common in Canterbury, Tunbridge Wells, Rochester, Faversham, Folkestone and Broadstairs.
Listed Buildings and Conservation Areas
Where you need permission to change windows, add external insulation or alter original features, keeping existing radiators can make a heat pump project far simpler. Kent has thousands of listed buildings, with historic centres in places such as Sandwich, Canterbury and Faversham.
Large Homes With High Heat Demand
Bigger detached houses and farmhouses can need more heat than a standard unit can comfortably deliver at low temperatures. Many such homes sit in villages around Sevenoaks, Marden and Wye.
Rural Off Gas Properties
Homes heated by oil or LPG often have older systems and higher fuel costs, and they gain most from switching. A high temperature model lets them move away from fuel deliveries without rebuilding the whole heating system.
Homes Where Radiator Upgrades Are Not Practical
Some homeowners simply do not want the disruption of new radiators, perhaps because of recent redecoration, limited wall space or valuable original cast iron radiators. A high temperature heat pump can respect those choices.
Is a High Temperature Heat Pump a Good Choice for Landlords?
A high temperature heat pump can be a good choice for landlords with older rental properties, because it allows a switch to low carbon heating with minimal disruption between tenancies. Fewer radiator changes mean less redecorating and a faster turnaround.
- EPC rules. Privately rented homes in England and Wales must currently be rated at least EPC E, and the government has set out plans to raise this to C by 2030. Replacing oil, LPG or old electric heating with a heat pump can help lift a rating.
- Grant support. Landlords can claim the £7,500 Boiler Upgrade Scheme grant on eligible properties.
- Tenant comfort. Radiators that feel as warm as a boiler are easy for tenants to understand, which can mean fewer complaints and call outs.
- No gas safety certificate. If a property becomes fully electric with no gas appliances, the annual Gas Safe landlord certificate is no longer needed there.
We work with landlords across Medway, Maidstone, Canterbury and Thanet, from Gillingham to Ramsgate.
Ready to Find Out if a High Temperature Heat Pump Is Right for Your Home?
If you are considering a high temperature heat pump, Guscott Heating can help you determine which system best suits your property. Request a free online heat pump estimate to explore your installation options, understand the likely costs and find out whether a high temperature or standard air source heat pump is more suitable for your heating requirements.
Request your free online heat pump estimate today and find out which system could work best for your property.
We can also explain how the £7,500 Boiler Upgrade Scheme grant could reduce your installation costs, subject to eligibility.
Guscott Heating provides expert air source heat pump installation across Kent and the wider South East of England.
Whether you own a period property, a rural farmhouse or a rental property, our MCS-certified team can help you explore suitable heating solutions based on your home’s requirements.
Frequently Asked Questions
Is a High Temperature Heat Pump the Same as a Hybrid Heat Pump?
A high temperature heat pump is not the same as a hybrid heat pump. A high temperature model is a standalone heat pump that does all the heating on its own. A hybrid pairs a heat pump with a gas, oil or LPG boiler that takes over on cold days. Hybrids do not qualify for the Boiler Upgrade Scheme, while high temperature heat pumps do.
Are High Temperature Heat Pumps With Propane Refrigerant Safe?
High temperature heat pumps that use propane (R290) are safe when installed correctly. The refrigerant is sealed inside the outdoor unit in a small quantity, and the system is built to strict safety standards. Your installer will follow the manufacturer’s guidance on positioning, such as keeping the unit a safe distance from drains, doors and windows.
Are High Temperature Heat Pumps Louder Than Standard Models?
High temperature heat pumps are generally no louder than standard models in normal use. The fan may sound a little busier on very cold days when the unit is working hardest. To count as permitted development in England, a heat pump must meet the MCS noise standard of 42 decibels at your neighbour’s nearest window, and we plan the position of the unit with this in mind.
Can a High Temperature Heat Pump Heat Water Hot Enough to Prevent Legionella?
A high temperature heat pump can heat stored water to 60°C or more, which is the temperature recommended to control legionella bacteria. Standard heat pumps often rely on an electric immersion heater for a weekly boost to reach this temperature. A high temperature model can usually do it on its own, which can save a little electricity.
How Long Does It Take to Install a High Temperature Heat Pump?
Installing a high temperature heat pump usually takes two to five working days, depending on the size of your home and whether a new hot water cylinder is needed. Because fewer radiators normally need replacing, installation can be quicker and less disruptive than a standard heat pump in an older home. Your heating is typically only off for a day or two.
