HEAT PUMPS / WEATHER COMPENSATION
The heating curve.
How outdoor temperature sets the flow temperature — and why small adjustments can improve comfort and efficiency.
01
Read the weather
The outdoor temperature tells the controller how much heat the home may need.
02
Set the flow
Colder weather calls for warmer water; milder weather allows a lower flow temperature.
03
Protect efficiency
Lower flow temperatures can improve COP and support a stronger seasonal SCOP.
04
Fine-tune comfort
Adjust the curve in small steps and watch how the whole home responds.
01 / THE BASICS
What is a heating curve?
A heating curve tells a heat pump what flow temperature to produce based on the outdoor temperature.
Heat pumps do not generate heat; they move it. The curve helps set the temperature at which that heat reaches the home.
When it’s colder outside, the system increases the flow temperature sent to your radiators or underfloor heating. When it’s milder outside, the flow temperature is reduced.
The aim is simple: provide just enough heat to keep the home comfortable without producing unnecessarily high water temperatures.
Think of the curve as the heat pump’s automatic weather compensation system.
02 / PERFORMANCE
Where the heating curve fits in.
The heating curve directly influences the flow temperature your heat pump produces. A curve set too high may keep the home warm, but it forces the heat pump to operate at higher temperatures than necessary.
Lower COP
Higher flow temperatures can reduce the heat produced for each unit of electricity.
More electricity
The compressor has to work harder to reach an unnecessarily high flow temperature.
Higher running costs
Poorer efficiency over the heating season increases electricity use and cost.
A well-optimised heating curve does the opposite. By keeping flow temperatures as low as possible for as much of the heating season as possible, the heat pump can achieve better efficiency throughout the year.
03 / COP AND SCOP
How better COP creates better SCOP.
The connection is straightforward. Every day your heat pump operates with a higher COP contributes to a higher SCOP.
If a heat pump runs at a COP of 4 during mild weather rather than a COP of 3, it uses less electricity to produce the same amount of heat.
When this improved performance is repeated over hundreds or thousands of operating hours throughout the year, the overall seasonal efficiency increases significantly.
This is why heating curve optimisation is often one of the quickest ways to improve heat pump performance without replacing any equipment.
04 / FLOW TEMPERATURE
Why lower flow temperatures matter.
Heat pumps are most efficient when the temperature difference between the heat source and the heating system is small.
01
At 35°C flow
If it is 7°C outside and the flow temperature is 35°C, the heat pump can operate very efficiently.
02
At 55°C flow
At the same 7°C outside, a 55°C flow makes the compressor work harder, reducing efficiency and increasing running costs.
HEAT PUMPS / WEATHER COMPENSATION
See the heating curve work.
Move the outdoor temperature, then raise or lower the curve. Watch the target water temperature, chart and heat-pump illustration respond.
This shifts the illustrative curve up or down; it is not a recommended setting for your home.
The heating curve
Colder outside → warmer water. Milder outside → cooler water.
This is why modern heat pump systems are often designed around:
- Larger radiators
- Underfloor heating
- Good insulation
- Effective weather compensation
These measures allow homes to stay warm while using lower flow temperatures.
05 / RECOGNISE THE SIGNS
Does the curve need adjustment?
Set too high
- Rooms overheating during mild weather
- Frequent cycling on and off
- Higher than expected electricity usage
- Elevated flow temperatures for long periods
Set too low
- Rooms struggling to reach target temperatures
- Reduced comfort during colder weather
The goal is finding the balance between comfort and efficiency.
06 / PRACTICAL TIPS
Make small changes and monitor the result.
If your heat pump uses weather compensation, consider the following:
01
Start low
Begin with the lowest heating curve that maintains comfort and only increase it if necessary.
02
Make small changes
Adjustments should be gradual. Small changes can have a significant impact on performance.
03
Monitor performance
Track room temperatures, flow temperatures, energy consumption and heat pump efficiency data.
04
Consider the system
The curve works alongside radiator sizing, insulation levels, thermostat settings and system controls.
Optimising all of these together delivers the best results.
THE MYWARMHOME VIEW
The link between comfort and efficiency.
A well-set heating curve keeps flow temperatures as low as possible while still maintaining a comfortable home. Lower flow temperatures improve COP, and consistently higher COP values throughout the heating season lead to a higher SCOP.
- Lower running costs
- Reduced carbon emissions
- Improved heat pump efficiency
- Better long-term performance
If rooms are uncomfortable, review heat emitters, controls and insulation as well as the curve before making a large adjustment.