The trade-off is efficiency. The hotter the water a heat pump makes, the more electricity it needs for each unit of heat, so a system running at 65°C has a lower seasonal efficiency than one running at 45°C. Good design still matters: weather compensation runs the unit cooler on mild days and only raises the temperature in the coldest weather, which keeps running costs down across the year.
A survey in Hertfordshire can compare a high-temperature unit with upsizing a few radiators, for homes anywhere in Hertfordshire. Older homes around Hertfordshire often need a discreet unit position, such as a rear courtyard, which the survey looks for first. Period houses in Hertfordshire with original cast-iron radiators may suit a high-temperature unit that works with them.
Who it suits
- Older homes where insulation improvements are limited
- Rooms with no wall space for a larger radiator
- Homes with microbore pipework that would be disruptive to replace
- Period and listed homes where the radiators are part of the character
Grants and rules for heat pumps in England
Homes in Hertfordshire can use the Boiler Upgrade Scheme, which takes £7,500 off the cost of an air source heat pump when it replaces fossil-fuel or electric heating. Replacing oil or LPG heating qualifies for £9,000 for installations from 21 July 2026 to 31 March 2027, and air-to-air systems for £2,500. The MCS-certified installer named in your quote applies for the grant and deducts it from the price.
Installing heat pumps is zero-rated for VAT across the UK until 31 March 2027. Since 29 May 2025, permitted development in England allows up to two air source heat pumps on a house, each up to 1.5 m³, with no blanket 1 m boundary rule — the installation must still meet the MCS planning standards, including the noise check. Listed buildings, flats and some conservation-area positions need extra consent, which we check at survey.
High-temperature heat pumps prices in Hertfordshire
Here are typical prices for high-temperature heat pumps in Hertfordshire, installed and including VAT. Use the guide price tool for a figure based on your home, then a survey confirms it in writing.
| Home | Typical size | Installed guide price | After £7,500 grant |
|---|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £10,000–£13,150 | £2,500–£5,650 |
| 2–3 bedroom terrace or semi | 5–7 kW | £11,050–£14,200 | £3,550–£6,700 |
| 3 bedroom semi or small detached | 6–9 kW | £12,600–£16,300 | £5,100–£8,800 |
| 4 bedroom detached | 8–12 kW | £14,700–£18,900 | £7,200–£11,400 |
| 5+ bedroom or larger older house | 11–16 kW | £17,350–£23,650 | £9,850–£16,150 |
Installed, inc VAT: unit, cylinder, controls, minor pipework and commissioning. A high-temperature unit typically adds £1,500–£3,000.
Towns we cover in Hertfordshire
We cover 17 towns in Hertfordshire for high-temperature heat pumps. Each links to local guide prices and the grant position for England.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Hemel Hempstead | HP2 | Berkhamsted | 7 h 47 min |
| Stevenage | SG1 | Hitchin | 7 h 45 min |
| St Albans | AL1 | Radlett | 7 h 47 min |
| Welwyn Garden City | AL8 | Hatfield | 7 h 46 min |
| Cheshunt | EN8 | Hoddesdon | 7 h 47 min |
| Hatfield | AL10 | Welwyn Garden City | 7 h 47 min |
| Bishop's Stortford | CM23 | Ware | 7 h 46 min |
| Hitchin | SG6 | Letchworth Garden City | 7 h 45 min |
| Hoddesdon | EN11 | Ware | 7 h 47 min |
| Letchworth Garden City | SG6 | Hitchin | 7 h 45 min |
| Harpenden | AL5 | St Albans | 7 h 46 min |
| Hertford | SG13 | Ware | 7 h 47 min |
| Berkhamsted | HP4 | Tring | 7 h 47 min |
| Ware | SG12 | Hertford | 7 h 46 min |
| Royston | SG7 | Letchworth Garden City | 7 h 44 min |
| Radlett | WD7 | St Albans | 7 h 48 min |
| Tring | HP23 | Berkhamsted | 7 h 47 min |
High-temperature heat pumps questions
Can a heat pump work with my existing radiators?
Often, yes, especially with a high-temperature unit. Standard heat pumps run most efficiently at 35–50°C, so some radiators may be too small at those temperatures. A high-temperature unit can run at around 65–75°C, so existing radiators can usually heat rooms much as they do with a boiler, at a cost in efficiency. The survey checks every radiator against its room's heat loss.
Do I still need a hot water cylinder?
Yes. Like other air-to-water heat pumps, a high-temperature unit heats a stored cylinder rather than supplying hot water on demand. Its higher output temperature can help the cylinder reach the temperature needed for its periodic legionella cycle with less reliance on the immersion heater. The cylinder is sized for your household at survey.
Is a high-temperature heat pump right for a listed building?
It can be, because it reduces the need to replace period radiators or lift historic floors for new pipework. The outdoor unit position still matters: in England, listed buildings need listed building consent for external works, and the other nations have their own rules. We check what applies at survey and look for discreet positions, such as a rear courtyard or behind an outbuilding.
Why do many high-temperature units use R290?
R290 is propane, a natural refrigerant with a very low global warming impact. Its properties make higher water temperatures more achievable than with some earlier refrigerants. Because it is flammable, manufacturers set clearance zones around the outdoor unit from windows, doors, drains and other openings, which the survey uses when choosing a position.