Background

The homeowner of a 4-bedroom detached property in Essex contacted us after experiencing persistently high electricity bills following the installation of an 11kW air source heat pump. The system had been commissioned and signed off, yet running costs were considerably higher than anticipated.

The client’s primary concern was whether the system had been correctly configured, as comfort levels were acceptable but energy usage seemed excessive.

Property & System Overview

• Property: 4-bedroom detached home

• Location: Essex

• Heat Pump: 11kW ASHP

• Emitters: Radiators

• Original Flow Temperature: 50°C constant

• Weather Compensation: Disabled

The system was operating at a fixed 50°C flow temperature regardless of external conditions.

Initial Observations

During our desktop system review, we immediately identified that the system was not operating dynamically. Rather than modulating output in response to outdoor temperatures, it was maintaining a constant high flow temperature.

For a property of this type, maintaining 50°C continuously is rarely necessary, particularly during mild or transitional weather. This approach significantly reduces system efficiency and increases compressor workload.

Technical Findings

After analysing system configuration and control strategy, we identified several core issues:

1. Weather Compensation Disabled
   The weather compensation function — designed to automatically adjust flow temperature based on outdoor conditions — had been turned off. This meant the heat pump was not optimising itself seasonally.

2. Excessive Flow Temperature
   A fixed 50°C flow temperature was unnecessarily high for much of the heating season. Higher flow temperatures reduce Coefficient of Performance (COP), increasing electricity consumption.

3. Hydraulic Imbalance
   The heating circuit had not been properly balanced. Some radiators were receiving more flow than necessary, creating uneven heat distribution and forcing the system to work harder overall.

Impact on Performance

These combined issues resulted in:

• Elevated electricity consumption

• Reduced seasonal efficiency

• Increased compressor runtime

• Lower system optimisation potential

Although the system was technically functional, it was not operating in a manner aligned with best practice heat pump design principles.

Corrective Strategy

Our recommendations focused on optimisation rather than hardware changes:

• Enable and configure weather compensation correctly

• Reduce flow temperature to a more appropriate curve starting around 38°C

• Balance the heating circuit to ensure even distribution

• Adjust pump settings to support lower-temperature operation

This approach allows the system to operate more dynamically and efficiently.

Outcome

Following adjustments:

• Flow temperature reduced from 50°C to an average of 38°C under comparable conditions

• System responsiveness improved

• Projected running costs decreased

• Comfort levels maintained or improved

• Overall seasonal performance enhanced

The homeowner gained confidence that the system was capable of efficient operation when correctly configured.

Key Takeaway

This case demonstrates that high running costs are often not due to equipment failure, but configuration strategy. Proper weather compensation setup and flow temperature optimisation are critical to achieving the efficiency heat pumps are designed to deliver.