One of the emerging options within the UK heating and hot water market is the hybrid system. ‘Hybrid’ typically means two heat sources operating under a single control strategy (for example, an air source heat pump (ASHP) combined with a gas/LPG boiler or water heater), which can be configured to share load across space heating and/ or domestic hot water (DHW).
Hybrid heating and hot water systems may draw on electricity (including on-site generation such as solar PV), solar thermal, heat pumps, and combustion fuels such as natural gas, LPG or oil. Some systems may also be compatible with lower-carbon fuels (for example BioLPG) and, where available and certified, hydrogen-blended gas supplies.
Hybrid systems typically combine a traditional combustion appliance (e.g., natural gas, oil or LPG) with a lower-carbon technology such as a heat pump or solar thermal. Properly designed controls can optimise operation based on outside temperature, flow temperature requirements, energy prices/tariffs, and space-heating and DHW demand, while still meeting comfort and hot water performance requirements.
For DHW systems such as continuous flow water heaters used alongside heat pumps, the heat pump can be sized to cover a significant proportion of the annual base load, with the combustion appliance providing ‘top-up’ heat for peak demand, high setpoints, or resilience. This can help maintain consistent DHW delivery, as long as it is correctly sized and commissioned.
Where electricity unit rates are higher than natural gas, a hybrid system can be operated to target lower running costs than an all-electric solution, depending on heat pump seasonal performance (COP/SPF), required flow temperatures, tariffs, and site demand profile. Some hybrid configurations may also reduce up-front costs compared with a full electrification approach, particularly where existing plant or distribution temperatures would otherwise require substantial upgrades.
A further potential benefit for the end-user is improved asset utilisation. If the system is correctly sized, commissioned and controlled (including avoiding excessive cycling), the workload can be shared between technologies, reducing stress on individual components and supporting long-term reliability. Actual service life will still depend on operating conditions, maintenance, and product selection.
"A hybrid system can be operated to target lower running costs than an all-electric heat pump solution. "
Hybrid systems can offer a practical route towards net zero objectives, particularly where full electrification is constrained by budget, space, electrical capacity, or emitter temperatures. Carbon reductions depend on how the system is designed and operated (including the proportion of annual heat delivered by the heat pump and the carbon intensity of the electricity supply), but a well-controlled hybrid can reduce emissions while maintaining service continuity and giving operators flexibility to manage running costs.
Smart solar, smart heat pump and smart condensing gas (including hydrogen-blend compatible where available) technologies can be integrated with controls that select the most appropriate heat source for prevailing conditions and objectives (for example cost, carbon, resilience), which can help reduce running costs and support long-term reliability when correctly designed and maintained.
REAL-WORLD SOLUTIONS
Hybrid heat pump systems provide practical, economic, and technical solutions as best exemplified by a recent installation at a luxury complex at Farringdon in the City of London. At this site, a hybrid water heating array of Low-GWP 50kW heat pumps plus bespoke thermal water stores, with optimised coil transfer to maximise heat pump performance, have been combined with 10 cascaded Hydrogen blends ready (I2HY20 certified) continuous flow water heaters.
The systems were delivered direct to site in one complete consignment, ready for installation. This expansive complex comprises a luxury hotel, prestigious and contemporary office space alongside affordable housing units.
The expansive retrofit site will pay respect to this heritage with many of the original features retained in the 150+ bedroom luxury hotel, almost 20,000 sq ft of opulent capital city office space and nine newbuild affordable residential units. The hotel group running the site already has one other unit in London with two more planned.
Hybrid systems have been installed and continue to offer seamless operational efficiency at many other locations. A national chain of gyms has successfully piloted a Low-GWP commercial ASHP with the aim of replacing their existing carbon intensive electric storage water heater systems, which rely on multiple electrical immersions.
The flexibility of the bespoke hybrid system design has ensured that some of the existing electric water heaters can stay in place as part of a cost-saving hybrid heat pump system while still reducing carbon emissions.
Each gym studio that has been measured revealed different kW load limits ranging from 8kW to 20kW. The gym owners were advised and then decided on the necessary decarbonising technology required for each individual gym, which included:
• Low-GWP R290 ASHP’s
• Electric storage water heaters
• Optimised heat pump cylinder coil cylinder or plate heat exchanger
• Unvented kit (cold water feed)
• System controls.
Consultants, contractors, specifiers, and installers are advised to consider using manufacturers and suppliers of decarbonising technology with proven records of successful installations of hybrid systems that equip locations with the ability to reduce costs and emissions.
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