How to run a heat pump efficiently: the settings that matter most

What to know first

This summary covers the settings that most affect comfort and efficiency in an air-to-water heat-pump system.

Heat pumps do not usually need to be operated like conventional boilers. For many homes, the practical approach is “low and steady”: keep heat available for longer, use a modest setback, and let the controls vary the water temperature.

This article concerns air-to-water heat pumps connected to radiators or underfloor heating. Air-to-air systems use different controls.

Why steady heating usually works better

A heat pump transfers heat most efficiently when it does not have to create very hot water or replace a large amount of lost heat quickly. Two brief heating periods copied from an old boiler schedule can leave a home slow to warm and may encourage higher flow temperatures.

Keeping the heating “on” does not mean the compressor runs continuously. It means the system is available to add heat when needed; the controls may slow, pause or restart the unit as demand changes.

Energy Saving Trust summarised the principle on 19 May 2026:

A setback must still suit the building and household. A small reduction can limit unnecessary demand, while a deep one may create a long recovery period.

What each heat-pump control actually does

Controller names vary, so this is a starting point rather than a substitute for the manual or handover settings.

These starting points reflect Energy Saving Trust’s operational advice and MCS design requirements. Manufacturer instructions and the commissioned design remain the final reference for a particular system.

Under MIS 3005-D, an MCS contractor must provide a handover pack containing commissioning documents, maintenance information, user manuals and warranties. The standard’s model handover document includes the design flow temperature, which is useful before changing advanced settings.

Set a schedule around the building, not old boiler habits

Start with the commissioned schedule. In many homes, heating is available across most or all of the day, with a lower target overnight or during a regular absence. Energy Saving Trust calls this reduction a “set-back” and advises against the large cool-down and recovery cycle common with boiler schedules.

The right setback is property-specific. A well-insulated home may cool slowly; a draughtier one may lose heat quickly. Underfloor heating also responds more slowly than radiators. Make small changes and judge comfort over several comparable days.

For a long absence, follow the manufacturer’s instructions for any holiday or frost-protection mode rather than assuming that the unit should be disconnected from its power supply.

Let weather compensation do the routine work

Flow temperature is crucial. Hotter water generally makes the heat pump work harder, but lowering it too far can leave rooms cold if the radiators, underfloor heating or water flow cannot release enough heat.

Weather compensation uses an outdoor sensor to raise the flow temperature in colder weather and lower it in milder conditions. This helps the heat pump match the building’s changing heat loss instead of producing the same water temperature all winter.

If the whole home is consistently warmer or cooler than intended, some controllers allow a small heating-curve “offset”. Energy Saving Trust suggests cautious one-degree reductions. Record the original setting and give each change time to show its effect.

MCS MIS 3005-D Issue 3.0 addresses higher-temperature designs. Where a proposed system is designed above 55°C, an alternative design at 55°C or below should also be supplied, and the efficiency and energy-consumption differences must be explained to the customer.

Expert insight

“The target is not a fashionable flow-temperature number. It is the lowest commissioned setting that keeps the intended rooms comfortable. One cold room may indicate a radiator, balancing or water-flow problem rather than a need to raise the whole system.”

Giles Crosse

Energy Editor

Experienced editor, journalist and communications consultant specialising in consumer energy and low carbon technologies.

• Editor and campaign author for Shell, EDF Energy and Good Energy.
• Consultant to the United Nations and contributor to the World Economic Forum.
• Journalist for Reuters, the BBC, The Economist and The Guardian.

More about Giles Crosse

Use radiator valves to trim rooms, not strangle the system

A thermostatic radiator valve, or TRV, reduces flow through a radiator as its room warms. This helps in bedrooms or rooms gaining heat from sunshine, cooking or appliances.

When many valves close, the heat pump has less active radiator area and water volume to absorb its output, which can increase cycling. A government study found this effect in a fixed-speed air source heat pump, although the 2011 test does not represent every modern inverter-controlled system. The system design takes priority.

Normal cycling is not automatically a fault. A 2012 government report found that rapid cycling can harm performance and said systems should be designed for cycles longer than around six minutes. That is design context, not a universal stopwatch test for every model.

Good to know

Use TRVs to maintain suitable room temperatures, not as the main way to correct a heating curve that is too high or poor system balancing.

Schedule hot water separately

A heat pump with a cylinder normally alternates between space heating and hot-water production. Many systems use “priority hot water”: the diverter valve directs the system to the cylinder until that cycle finishes, then returns to space heating. Radiators may therefore cool temporarily.

Schedule normal reheating before likely demand and avoid unnecessary reheating when little hot water is used. The right times depend on household use, cylinder size, control strategy and any time-based electricity tariff.

The ordinary hot-water setpoint is separate from the higher-temperature bacterial-control or pasteurisation cycle. MCS MIS 3005-D Issue 3.0, dated 5 December 2025, states:

MCS does not set one universal pasteurisation frequency in that clause. It says a bacterial risk assessment can help determine the frequency where periodic pasteurisation is used. Manufacturer, installer and site-specific instructions therefore matter.

Many systems use an immersion or booster heater to complete this higher-temperature cycle. A temporary rise in electricity use during it does not by itself show a fault.

A careful way to fine-tune the controls

1. Find the baseline. Check the handover pack, manual and design flow temperature. Record existing settings.

2. Stabilise the schedule. Keep the room target and heating periods consistent long enough to understand the home.

3. Change one setting. A small curve offset or one-degree adjustment is easier to assess than several changes together.

4. Compare like with like. Note outdoor weather, indoor comfort, hot-water use and booster operation.

5. Restore a setting when needed. Go back if rooms become cold, recovery is impractically slow or faults appear.

6. Escalate persistent problems. Ask a competent heat-pump professional to check heat loss, emitters, water flow, balancing, sensors and controls.

This sequence is a cautious editorial interpretation of the Energy Saving Trust advice to make small heating-curve changes and seek installer support where settings or performance are unclear.

Do not judge performance from electricity use alone. MCS identifies room temperatures, hot-water use, occupancy, ventilation, weather, flow temperature and system design as factors affecting demand or efficiency. A colder week can therefore use more electricity even when the underlying system efficiency has not deteriorated.

When the settings may not be the real problem

Contact the installer, manufacturer or a suitable heating engineer if the system shows recurring faults, cannot heat particular rooms, relies on the booster unusually often, loses pressure or short-cycles. Dirty filters, closed valves, undersized radiators, poor water flow or sensor problems can resemble a controls issue.

For a recent MCS installation, the handover pack should contain the design information, manuals, warranties and contractor details needed for a review. Avoid password-protected installer menus and do not disable safety or bacterial-control functions without appropriate instructions.

Key takeaways

• Run the heating for longer periods and use a modest setback rather than repeated hot bursts.

• Keep flow temperature as low as the commissioned system can comfortably support.

• Use weather compensation for routine outdoor-temperature changes.

• Adjust one setting at a time and record the original value.

• Use TRVs to trim rooms while leaving enough emitter area for stable operation.

• Schedule normal hot-water reheating around demand, but retain bacterial control.

• Seek help for persistent cold rooms, frequent booster use, faults or rapid cycling.

These conclusions combine current Energy Saving Trust operating advice with MCS design and handover requirements and the limitations identified in government cycling research.

Frequently asked questions