Rinnai’s Peter Seddon discusses hybrid systems and the separate technologies that combine to create an efficient configuration of components that produce heating and hot water. Continue reading to find out how a hybrid system operates and how gas and electricity are used to optimise system longevity, efficiency and performance.
A possible solution to UK decarbonisation is hybrid systems that accept two forms of fuel to ensure cost-effective and smooth operational performance that produces heat and hot water. What is a hybrid system and how do they operate to the benefit of the end-user?
Hybrid technology accepts two separate forms of power, one would be either natural gas or LPG, alongside solar thermal or a heat pump. Hybrid systems are designed to optimise factors such as outside temperature, current energy prices, property heating and DHW demand. Once data is collected Smart software will select the most economic and energy efficient fuel option to guarantee customer satisfaction.
For smart DHW hot water systems such as continuous flow water heaters used with heat pumps, the renewable heat generator provides the base load as the water heaters “top up” the temperature. This approach is inherent within the system and ensures optimal performance.
Using two separate energies offers a range of benefits for UK retrofit projects in a domestic or commercial application. The first advantage is from a financial viewpoint: as electric costs are higher than natural gas, utilising a system that accepts both renewable electricity and traditional fuel sources mean that costs will be lower and more manageable when compared to an exclusively electrical system. From a capital expenditure perspective, the cost of a hybrid is often lower than a full electric system creating lower whole of life costs.
In terms of operational performance, a hybrid heating and hot water system combines two technologies that ensures energy efficiency whilst supporting operational consistency. A hybrid system will benefit from the incorporated heat pump or solar thermal technology during favourable weather conditions whilst using the auxiliary appliance during periods of colder conditions. This will optimise the strengths of each technological approach in separate weather condition circumstances; the addition of a combustion-based water heating technology will boost the renewable base load to ensure DHW performance.
A further benefit for the end-user is that both lifecycles of each technology are lengthened. As each technology does not have to apply full effort to satisfy demand, component and overall system longevity will be increased due to a lessening of required workload.
Hybrid systems offer a practical route for environmental objectives to be accomplished. As not all customers can fully financially commit to decarbonising practises, an alternative mix of technologies that incorporates both renewable and traditional technologies and fuels is offered to bridge this gap. This practical approach introduces customers to alternative and clean energies whilst maintaining control over energy costs by still relying on conventional and more cost-effective methods of energy usage. Hybrid systems are particularly attractive for hotels, leisure facilities, healthcare environments, education buildings and multi-residential developments where high domestic hot water demand coincides with ambitious decarbonisation targets.
The Hybrid approach can also be instrumental within buildings that do not have the space, infrastructure or plant room facilities for full electrification and the increase in store hot water volumes.
A hybrid system is comprised of several features, components, technologies and fuels. The main elements of a hybrid heating and hot water system are listed below.
- Heat Pump: The renewable backbone of the system. Most hybrid systems utilise air source heat pumps (ASHPs). Ground source heat pumps (GSHPs) are also viable for specific applications, particularly in commercial settings.
- Condensing Gas Boiler / Water Heater: A high efficiency water heater serves as the auxiliary heat source. Modern condensing water heaters are designed to extract as much heat as possible from combustion gases, increasing energy efficiency.
- Solar Panels: When solar thermal collectors are included, they can contribute heat to the system directly or to a buffer tank. This heat can then be drawn upon before the system calls for either the heat pump, gas boiler and water heaters making it more energy efficient.
- Control Unit / Smart Thermostat: The ‘brain’ of the hybrid system, responsible for deciding which heat source to use based on real time conditions. Many units are integrated with weather compensation and predictive algorithms.
- Buffer Tank / Hot Water Cylinder: Optional but recommended for systems that provide domestic hot water (DHW). The buffer tank helps to smooth out demand fluctuations and improve efficiency. Other cylinders can include buffers for minimum water content and for additional hot water demand.
- Sensors and Meters: These measure temperature, flow rates, and energy consumption, feeding data back to the control system to enable automated switching.
Hybrid technology is a growing solution for commercial or domestic property owners who seek to limit carbon output and who cannot afford to financially commit to a true carbon neutral heating and hot water system. The profile of hybrid technology is becoming far more discernible both in the UK and Europe.
The HHGB (Hybrid Heating Great Britain) is a consortium of electric and gas suppliers, heat pump manufacturers and software solution providers. This coalition has recently released a report entitled: “Hybrid Heating Systems: Accelerating Decarbonisation in Britain’s Homes.” This report references analysis carried out by the DESNZ (Department of Energy Security and NetZero) that states hybrid technology can result in cost savings of up to 30% when compared to an air source heat pump.
The report also details a number of trials that have been carried out inside the UK and the Netherlands. As the Dutch housing stock is comparable to the UKs in terms of materials used in construction and the dimensions that are incorporated into the planning and building phases, any study that states a financial or operational benefit from home heating and hot water production in one country, can be also applied to the other.
The Netherlands was the location for a recent study conducted by the Association for Sustainable Heat, a leading Dutch trade association that represents manufacturing and industrial companies that specialise in producing sustainable and efficient property heating.
This particular study explored the effect of hybrid heating on 200 homes in the Netherlands. It was found that on average energy costs had annually decreased by £653, insinuating that hybrid heating and hot water provision could be the better option for customers in a financial context.
An additional trial on a smaller scale has also been conducted in South Belfast during 2024 by Pheonix Energy, the largest and most prominent gas distribution company in Northern Ireland. The trial aimed to explore the potential of hybrid technology for Northern Irish customers.
The key findings of the trial found that heating costs were 16% less than a traditional gas boiler and 20% lower than a standalone heat pump. Further reductions include a 51% removal of emissions when compared to gas boilers. Operational observations found that 84% of the heating load was covered by the heat pump and the remaining 16% was provided by the gas boiler. As the traditional element of the hybrid system (the gas fired boiler) managed peak load, the heat pump itself operated at 354% average efficiency.
A final noteworthy trial regarding hybrid systems was held in seven domestic properties in Wales, South-West England and London between 2020 and 2022. The trial was conducted by WWU (Wales and West Utilities) who manage the gas network across the South-West of England and Wales, Passiv – a UK smart energy technology company, Delta-EE, a Scottish energy consultancy and research firm, alongside the Imperial College of London.
The key findings of this trial concluded that compact hybrid heating systems could potentially deliver £100 in annual energy system cost savings per installation. Up to 14 million homes could be suited to hybrid heating. Smart controlled hybrid technology can provide a flexible approach to fuel utilisation once external factors such as grid stress or outside temperature are taken into account. The trial also found that 79% of participants were attracted to hybrid heating, whilst only 16% were aware of technologies beyond gas boilers.
Hybrid systems offer an immediately deployable pathway towards lower-carbon heating and hot water provision. By intelligently combining renewable technologies with high-efficiency gas appliances, building owners can reduce emissions, manage operational costs and maintain reliable performance without the infrastructure challenges often associated with full electrification. For many UK domestic and commercial properties, hybrid technology provides a practical bridge between today’s energy realities and tomorrow’s net zero ambitions.
RINNAI OFFERS CLEAR PATHWAYS TO LOWER CARBON AND DECARBONISATION PLUS CUSTOMER COST REDUCTIONS FOR COMMERCIAL, DOMESTIC AND OFF-GRID HEATING & HOT WATER DELIVERY.
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- Rinnai’s range of decarbonising products – H1/H2/H3 – consists of hot water heating units in gas/BioLPG/DME, hydrogen ready units, electric instantaneous hot water heaters, electric storage cylinders and buffer vessels, a comprehensive range of heat pumps, solar, hydrogen-ready or natural gas in any configuration of hybrid formats for either residential or commercial applications. Rinnai’s H1/2/3 range of products and systems offer contractors, consultants and end users a range of efficient, robust and affordable low carbon/decarbonising appliances which create practical, economic and technically feasible solutions.
- Rinnai is a world leading manufacturer of hot water heaters and produces over two million units a year, operating on each of the five continents. The brand has gained an established reputation for producing products that offer high performance, cost efficiency and extended working lives.
- Rinnai products are UKCA certified, A-rated water efficiency, accessed through multiple fuel options and are available for purchase 24/7, 365 days a year. Any unit can be delivered to any UK site within 24 hours.
- Rinnai offer carbon and cost comparison services that will calculate financial, and carbon savings made when investing in a Rinnai system. Rinnai also provide a system design service that will suggest an appropriate system for the property in question.
- Rinnai offer comprehensive training courses and technical support in all aspects of the water heating industry including detailed CPD’s.
- The Rinnai range covers all forms of fuels and appliances currently available – electric, gas, hydrogen, BioLPG, DME solar thermal, low GWP heat pumps and electric water heaters More information can be found on Rinnai’s website and its “Help Me Choose” webpage.
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