Heat pumps
Heat pumps are a low-carbon alternative to traditional gas, oil, or electric boilers. Instead of generating heat by burning fuel or using resistive electricity, they move existing heat from the outside air, ground, or water into your home.
Because they move heat rather than generate it, heat pumps are highly efficient—often providing 3 to 4 units of heat for every 1 unit of electricity they use.
How heat pumps work
A heat pump works like a refrigerator in reverse. It uses a refrigerant cycle to absorb heat from the environment, compresses it to increase the temperature, and transfers that heat into your home’s central heating system (radiators or underfloor heating) and hot water tank.
Why choose a heat pump?
- Lower carbon emissions: Heat pumps can reduce your home’s carbon footprint by up to 70% compared to a gas boiler (Source: Energy Saving Trust).
- Highly efficient: Operating at 300-400% efficiency, they are far more efficient than the best condensing boilers (90-95%).
- Long lifespan: Heat pumps typically last 15-20 years, longer than most modern gas boilers.
- Government funding: You can get a £7,500 grant through the Boiler Upgrade Scheme to help with installation costs.
Fabric First: Heat pumps work most efficiently in well-insulated homes. Before installing a heat pump, we strongly recommend checking your insulation levels and draught-proofing your property.
Tools
- Heat pump calculator — Estimate the right system size and potential savings for your home.
- Running cost estimator — Compare your current heating costs with a heat pump.
Guides
- Choosing a heat pump — Which type is right for your property?
- Installation process — What to expect during the transition.
- Financial support and grants — BUS grants and 0% VAT.
- Air source vs Ground source — A detailed comparison of technologies.
- Maintenance and servicing — Keeping your system running efficiently.
- Radiator sizing guide — Ensure your radiators are ready for low flow temperatures.
- Running costs — Understanding COP and electricity usage.
- Noise levels and planning — Permitted development and positioning.
- Case studies — Real-world examples of heat pump retrofits.
Troubleshooting & common problems
Issues you might encounter with your heat pumps and how to solve them safely.
Radiators lukewarm with heat pump
Why your radiators don't feel 'hot' like they did with a gas boiler, and whether it's actually a problem.
Heat pump flow temperature too high
Why a high flow temperature is reducing your heat pump's efficiency and how to lower it to save money on your electricity bills.
Heat pump icing up
Identifying when ice on your outdoor unit is a normal part of operation and when it indicates a technical fault that needs fixing.
Typical UK costs and savings
Costs vary by property size, emitter upgrades (radiators/underfloor), and whether ground works are required.
- Air source heat pump (ASHP): typically £7,000–£14,000 before grants.
- Ground source heat pump (GSHP): typically £18,000–£35,000 before grants.
- Boiler Upgrade Scheme (BUS): grant of £7,500 towards eligible installations in England and Wales.
Running costs depend on your home’s heat demand, the system’s efficiency (seasonal COP), and your energy tariff. As a rule of thumb:
- A well‑designed ASHP with a seasonal COP of 3.0 uses about 1 kWh of electricity to deliver 3 kWh of heat.
- Smart time‑of‑use tariffs and weather/flow‑temperature optimisation can materially reduce running costs compared with flat tariffs.
Payback periods vary widely. Many households prioritise comfort and carbon reductions; others achieve favourable economics by combining fabric upgrades (insulation, air‑tightness), low flow temperatures, and smart tariffs.
Common pitfalls to avoid
- Undersized or unbalanced radiators leading to high flow temperatures and poor efficiency.
- Inadequate insulation or uncontrolled drafts increasing heat demand.
- Lack of weather compensation and poor commissioning.
- Choosing non‑certified installers (risking BUS grant ineligibility and performance issues).
Frequently asked questions
Do heat pumps work in cold weather?
Yes. Modern systems maintain performance well below 0°C. Efficiency (COP) falls as it gets colder, but correct sizing and low flow temperatures keep homes comfortable.
Will I need bigger radiators?
Often, yes. To run efficiently at lower flow temperatures (e.g., 40–50°C), some rooms may need larger radiators or underfloor heating.
Are heat pumps noisy?
Outdoor units produce a low hum. Good siting, anti‑vibration mounts, and acoustic enclosures keep noise within planning limits.
Do I need planning permission?
Most single ASHPs for houses are permitted development if they meet siting/noise limits. Flats, listed buildings, and some locations may need consent—check local rules.
How long do heat pumps last?
Typically 15–20 years for the outdoor unit; indoor components can last longer with maintenance.
Can I keep my existing hot water cylinder?
Often you’ll replace it with a heat‑pump‑ready cylinder (larger coil) for faster reheating and legionella protection.
Sources
- Energy Saving Trust — Heat pumps: efficiency, costs, performance.
- GOV.UK — Boiler Upgrade Scheme (BUS) guidance and eligibility.
- MCS — MIS 3005 (Heat pump installation standard) and certified installer search.
- Planning Portal — Permitted development rights for heat pumps in England/Wales.
Written by NetZeroNow Editorial Team | Last updated on 2026-03-23