Hybrid Heating Performance Case Study

This hybrid heating case study examines the real-world performance of a monitored Alpha E-Tec Hybrid installation over a 12-month period. The project evaluated seasonal efficiency, running costs and carbon emissions in an occupied home in Northern Ireland, demonstrating how hybrid heating can provide a practical lower-carbon solution for existing properties.

Project Overview

At the end of 2024, solv installed an Alpha E-Tec Hybrid heating system at a property in Wandsworth Gardens, East Belfast, combining an Air Source Heat Pump with a gas boiler. The installation was supported by Phoenix Energy and Alpha, with both units installed externally to minimise impact within the home during installation and free up additional storage space. In February 2025, a heat monitoring system supplied by OpenEnergyMonitor was installed to collect live performance data and assess real-world system performance, homeowner comfort and carbon reduction across a full year of operation.

The property:

Semi-detached house
EPC rating: E
Occupancy: 2 adults, 1 baby
10.5ºC average outside temperature

Heat Source Contribution

Although this EPC E property would traditionally be considered challenging to decarbonise due to its age, heat loss and limited retrofit opportunities, the Air Source Heat Pump still provided almost 44% of the home’s annual heating demand. Despite being intentionally undersized as part of the hybrid design, the heat pump made a significant contribution, with the gas boiler supplying the remaining 56% during periods of increased demand.

The results demonstrate how hybrid systems can bridge the gap between traditional heating and full electrification, offering a practical lower-carbon solution for many older homes across Northern Ireland without the need for extensive insulation upgrades.

The monitored hybrid heating system maintained strong seasonal efficiency across varying outdoor temperatures throughout the year. The Air Source Heat Pump (ASHP) element of the hybrid system achieved a COP above 3 during most heating months, demonstrating efficient operation even in colder weather. Lower efficiency recorded during warmer summer periods reflects reduced space heating demand and is not a reflection on the heat pump’s contribution.

Carbon Emissions Comparison

Compared to a traditional gas-only heating system, the hybrid installation achieved a substantial reduction in carbon emissions across the monitoring period. The system produced approximately 808kg of CO₂ emissions, compared to an estimated 1,583kg from an equivalent gas setup — representing a carbon reduction of almost 49% while continuing to maintain homeowner comfort and heating performance.

The hybrid heating system delivered a significant reduction in carbon emissions across the monitoring period, producing almost 49% less CO₂ than a comparable traditional gas-only heating system. Energy demand was also highest during the colder winter months, demonstrating the system’s ability to maintain efficient and reliable performance throughout periods of increased heating demand.

Running Cost Comparison

The monitored hybrid heating system achieved the lowest annual running costs across the compared heating technologies.

Gas £1,229.13
ASHP £1,322.72
Hybrid £1,148.14

Based on the monitored data, the hybrid system delivered estimated running cost savings of approximately 7% compared to a traditional gas-only heating system and 13% compared to a standalone Air Source Heat Pump system, while continuing to provide significantly lower carbon emissions.

Key Findings

Based on the monitored results of this case study, the hybrid heating system demonstrated strong real-world performance within an occupied Northern Ireland home, with no system/insulation upgrades, delivering significant carbon reductions alongside lower annual running costs when compared to traditional gas-only and standalone Air Source Heat Pump systems.

49% reduction in carbon emissions
775kg CO₂ saving
3.4 COP average seasonal system efficiency

The findings support hybrid heating as an effective lower-carbon solution for existing housing stock, capable of maintaining homeowner comfort and reliable heating performance while helping reduce both emissions and energy costs.