Answer first
Lower the heating curve only in small steps and observe the home through representative weather. If rooms miss their design temperature, fix emitter, flow or heat-loss problems rather than accepting discomfort.
The best result is a surveyed system designed to meet each room’s heat loss at the lowest practical flow temperature, then commissioned with weather compensation.
The useful target is the lowest water temperature that maintains room comfort
View sourceRadiator output must be checked at the proposed temperatures
View sourceThe target temperature should fall as outdoor conditions become milder
View sourceAsk FLO about flow temperature and comfort
Share the property, current heating and the question holding up your decision. FLO will explain what to check next without pushing you into a survey.
Why temperature affects efficiency
The compressor has to create a larger temperature lift when outdoor air is cold or heating water is hot. Reducing an unnecessary lift can improve performance.
This is why a product’s rated efficiency changes between low- and high-temperature applications. It is also why one static flow target for every day can waste energy.
Radiators set the practical limit
Radiators release less heat as their average temperature moves closer to room temperature. The design must check the manufacturer output correction at the proposed flow and return temperatures.
Larger radiators, additional emitters or better heat retention may allow a lower curve. Simply turning the water down cannot create missing output.
Tune weather compensation carefully
Weather compensation raises water temperature as the weather becomes colder and lowers it in mild conditions. Start from the commissioned curve.
Make one small change, allow the building to settle and record room temperatures. Underfloor heating and heavy masonry may take longer to show the effect.
Look for system issues before raising the curve
One cold room may indicate balancing, air, valve or emitter problems. A cold whole home may point to curve, schedule, flow, filters or capacity.
Permanent boosts can hide the cause while increasing electricity use. Ask for technical aftercare if the design temperature cannot be maintained.
What to read next
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Questions people also ask
What flow temperature should my heat pump use?+
There is no universal number; it depends on heat loss, emitters, weather and design.
Can I lower it myself?+
Use only normal user controls, make small changes and keep the commissioned settings recorded.
Will bigger radiators help?+
They can deliver the same room heat at a lower water temperature if correctly selected and balanced.
Evidence used for this answer
Figures are explained in context and links go to the independent source. Prices, tariffs, scheme rules and standards can change, so check the source again before making a financial or technical decision.
- Energy Saving Trust: the most efficient way to run a heat pumpGuidance on weather compensation, longer run periods, setbacks, radiators, hot water and smart energy use.
- MCS heat-pump design standardTechnical requirements for heat loss, equipment selection, domestic hot water and system design.
- MCS domestic heat-pump guideConsumer guidance covering design, installation, controls, handover and maintenance.
- Energy Systems Catapult: heat-pump performance analysisMeasured seasonal performance and cold-weather operation from the Electrification of Heat demonstration project.