High Temperature Heat Pumps: When You Need One
Published: March 2026 | Reading time: 8 minutes
Standard air source heat pumps work best at flow temperatures of 35-55°C. That's fine for homes with underfloor heating or generously sized radiators, but what if your home has small, older radiators that need 60°C or above to heat the rooms properly? Or you have a period property where replacing radiators isn't practical?
This is where high temperature heat pumps come in. They can deliver flow temperatures of 65-80°C — close to what a gas boiler provides — while still being significantly more efficient than direct electric heating. They're not the right choice for every home, but for certain properties, they solve a real problem.
What Is a High Temperature Heat Pump?
A high temperature heat pump works on the same principle as a standard unit — extracting heat from outdoor air using a refrigerant cycle. The difference is in the compressor technology and refrigerant used, which allow it to achieve much higher output temperatures.
- Standard heat pump: Maximum flow temperature typically 55-60°C (most efficient at 35-50°C)
- High temperature heat pump: Maximum flow temperature 65-80°C (some models up to 90°C)
High temperature models typically use cascade or two-stage compressor systems, or specialist refrigerants like R290 (propane) or CO2, to achieve these higher temperatures.
When Do You Need a High Temperature Heat Pump?
A high temperature system makes sense in specific situations:
1. Older Properties with Original Radiators
Many Victorian, Edwardian, and inter-war properties have small cast iron or pressed steel radiators that were designed for gas boiler flow temperatures of 70-80°C. At 45-50°C (standard heat pump temperatures), these radiators simply don't emit enough heat to warm the rooms adequately.
Replacing all the radiators in a period property can be expensive (£3,000-5,000+), disruptive, and sometimes undesirable — particularly if you have decorative cast iron radiators that are part of the home's character.
A high temperature heat pump can run these existing radiators at 65-70°C, providing adequate heating without any radiator changes. For a detailed look at whether your radiators need changing, see our guide on radiators for heat pumps.
2. Listed Buildings and Conservation Areas
In listed buildings, changing radiators or internal heating infrastructure may require listed building consent. Period features — including original radiators — are often protected. A high temperature heat pump allows the switch from gas without altering the building's historic fabric.
3. Properties Where Radiator Replacement Is Impractical
In some homes, the radiators are built into the architecture — recessed into walls, fitted under window seats, or integrated into cabinetry. Replacing or upsizing them would require significant building work. A high temperature system avoids this entirely.
4. Hard-to-Insulate Properties
Solid-walled properties (common in pre-1930s housing stock) are more expensive and complex to insulate than cavity wall houses. If your property has high heat loss due to solid walls, single glazing, or other insulation challenges, the heating system needs to work harder. Higher flow temperatures can compensate for higher heat loss without requiring extensive (and costly) insulation upgrades first.
5. Commercial and Larger Properties
Some commercial buildings, schools, churches, and larger residential properties have heating systems designed for high temperatures. Retrofitting these with standard heat pumps would require replacing the entire heat distribution system — a high temperature heat pump connects to the existing infrastructure.
Costs: High Temperature vs Standard Heat Pumps
High temperature heat pumps cost more than standard models — both to buy and to run. Here's the trade-off:
Purchase and Installation
| Type | Typical Installed Cost (3-bed home) |
|---|---|
| Standard air-to-water heat pump | £8,000 – £12,000 |
| High temperature heat pump | £10,000 – £16,000 |
The premium is typically £2,000-4,000 above a standard system. However, this needs to be weighed against the cost of radiator upgrades that a standard system might require. If you'd need £3,000-5,000 of radiator replacements for a standard heat pump, the high temperature option may actually be cheaper overall.
Running Costs
This is where the trade-off becomes important. Higher flow temperatures mean lower COP:
| Flow Temperature | Typical COP | Approximate Annual Cost (3-bed) |
|---|---|---|
| 35°C (UFH) | 3.5 – 4.5 | £500 – £700 |
| 45°C (large radiators) | 3.0 – 3.8 | £600 – £850 |
| 55°C (standard radiators) | 2.5 – 3.2 | £750 – £1,000 |
| 65°C (high temp) | 2.2 – 2.8 | £850 – £1,150 |
| 75°C (high temp) | 1.8 – 2.5 | £1,000 – £1,350 |
At 65°C, a high temperature heat pump achieves a COP of around 2.2-2.8. That's still significantly better than a direct electric heater (COP of 1.0) and broadly competitive with a gas boiler on running costs, depending on electricity and gas prices.
At 75°C+, efficiency drops further. At these temperatures, the running cost savings versus gas become marginal — the main benefit shifts to decarbonisation rather than bill savings.
The BUS Grant
High temperature heat pumps are eligible for the Boiler Upgrade Scheme grant (£7,500), provided they meet MCS standards. This significantly reduces the upfront cost premium.
Available Models in the UK
Several manufacturers now offer high temperature heat pump models for the UK market:
- Vaillant aroTHERM plus: R290 refrigerant, flow temperatures up to 75°C, widely available through Vaillant's installer network
- Daikin Altherma 3 H HT: Flow temperatures up to 70°C, versatile range of capacities
- Mitsubishi Ecodan R290: Newer R290 models achieving up to 75°C, building on the Ecodan's excellent track record
- Samsung EHS Mono HT: High temperature variant with competitive pricing
- NIBE S-Series: Flow temperatures up to 75°C, excellent cold-climate performance from Swedish engineering
- Bosch Compress 7800i: Up to 75°C, growing UK availability
The market for high temperature heat pumps is expanding rapidly as manufacturers recognise the need for retrofit-friendly solutions in the UK's older housing stock.
High Temperature Heat Pumps vs Other Solutions
A high temperature heat pump isn't the only option for older properties. Let's compare the alternatives:
Option 1: Standard Heat Pump + New Radiators
- Cost: £8,000-12,000 (heat pump) + £3,000-5,000 (radiators) = £11,000-17,000
- Running costs: Lower (higher COP at lower flow temperatures)
- Disruption: Higher (radiator replacement involves plumbing and decoration work)
- Long-term winner: Better efficiency means this option pays back over 10-15 years
Option 2: High Temperature Heat Pump + Existing Radiators
- Cost: £10,000-16,000 (no radiator changes needed)
- Running costs: Higher (lower COP at higher flow temperatures)
- Disruption: Lower (minimal internal changes)
- Best for: Properties where radiator replacement is costly, impractical, or undesirable
Option 3: Hybrid Heat Pump (Heat Pump + Gas Boiler)
- Cost: £8,000-12,000 (heat pump) + existing boiler
- Running costs: Variable — heat pump handles mild weather, gas boiler kicks in during cold snaps
- Disruption: Low (keeps existing system, adds heat pump)
- Downside: Still uses gas, doesn't fully decarbonise, boiler will need replacing eventually
Option 4: Standard Heat Pump + Partial Radiator Upgrade
- Cost: £8,000-12,000 (heat pump) + £1,000-2,000 (a few radiators)
- Running costs: Moderate (flow temperature of 50-55°C as compromise)
- Disruption: Moderate
- Best for: Properties where only a few radiators are undersized
The right choice depends on your specific property, budget, and priorities. Your installer should present these options after completing a proper heat loss survey.
Efficiency Tips for High Temperature Heat Pumps
Even with a high temperature system, you can improve efficiency:
1. Use Weather Compensation
Don't run at 70°C all year round. Weather compensation automatically reduces the flow temperature on milder days. Your system might run at 65°C in January but only 45°C in October — significantly boosting average seasonal efficiency.
2. Insulate Where You Can
Even if your property is hard to fully insulate, targeted improvements make a difference. Loft insulation (if accessible), draught-proofing around doors and windows, and internal wall insulation in key rooms all reduce heat demand and allow lower flow temperatures.
3. Consider Hybrid Approach Room by Room
You might install a high temperature heat pump but also upgrade the radiators in one or two key rooms (e.g., the living room). This allows you to run at slightly lower flow temperatures while still keeping the original radiators elsewhere.
4. Use the Lowest Temperature That Works
Don't assume you need 75°C just because your old boiler ran at that temperature. Try 65°C and see if the house stays warm. Many homeowners find their radiators cope at lower temperatures than expected — especially after adding loft insulation or draught-proofing.
Frequently Asked Questions
What is a high temperature heat pump?
A heat pump designed to deliver water at 65-80°C (some up to 90°C), compared to standard models that typically max out at 55-60°C. They use advanced compressor technology or specialist refrigerants to achieve these higher temperatures while maintaining reasonable efficiency.
Are high temperature heat pumps less efficient?
Yes, at the same flow temperature comparison point. A high temperature heat pump running at 70°C will have a lower COP (around 2.2-2.8) than a standard heat pump running at 45°C (COP 3.0-3.8). However, the high temperature model may still be the more practical and cost-effective choice if the alternative involves extensive radiator replacements.
Do high temperature heat pumps qualify for the BUS grant?
Yes. High temperature air-to-water heat pumps are eligible for the £7,500 Boiler Upgrade Scheme grant, provided they're installed by an MCS-certified installer and meet the scheme's requirements.
Can I use a high temperature heat pump with underfloor heating?
Yes, but there's no benefit to doing so. Underfloor heating works optimally at 30-40°C, so a standard heat pump would be more efficient and cheaper. A high temperature model is designed for situations where you need higher flow temperatures — if you have UFH, you don't.
How much noisier are high temperature heat pumps?
Not significantly. Noise levels are comparable to standard models — typically 40-55 dB at one metre. The higher operating temperatures don't substantially affect outdoor noise output.
Is a high temperature heat pump right for my Victorian terrace?
Possibly. Victorian terraces often have small radiators, solid walls, and high ceilings — all factors that favour a high temperature system. However, a proper heat loss survey is essential. Some Victorian properties work well with a standard heat pump after modest radiator upgrades; others genuinely need high temperature capability.
Will high temperature heat pumps get cheaper?
Almost certainly. As the UK retrofit market grows and more manufacturers enter the high temperature segment, competition will drive prices down. The technology is also improving — expect to see better COPs at high temperatures as compressor and refrigerant technology advances.
The Bottom Line
High temperature heat pumps bridge the gap between modern heating technology and the UK's older housing stock. If your property has small radiators, solid walls, or period features you want to preserve, a high temperature system lets you switch to a heat pump without ripping out your existing heating infrastructure.
The trade-off is lower efficiency and higher running costs compared to a standard heat pump operating at lower temperatures. But compared to the cost of extensive radiator replacements — or continuing to burn gas indefinitely — a high temperature heat pump is a practical, cost-effective solution for many UK homes.
The best first step is a proper heat loss survey that assesses your specific property. Use our heat pump calculator for an initial estimate, or get free quotes from MCS-certified installers who can recommend the right system for your home.