Are you considering installing a hybrid heat pump? Here we explore their pros, cons, running costs and installation costs.
- What is a Hybrid Heating System?
- How does a hybrid heat pump system work?
- Why do I need the gas boiler if the heat pump can heat my home?
- What efficiency can I expect with a Hybrid Heat Pump Boiler?
- Are they suitable for all property types?
- Are hybrid heat pumps noisy?
- Hybrid Heat Pump Running Costs UK
- Will a hybrid heat pump save you money?
- Is there a specific type of hybrid boiler system I need?
- Hybrid Heat Pump Costs
- What are the benefits of installing a hybrid heat pump?
- Disadvantages of Hybrid Heat Pumps in the UK
Thinking of installing a hybrid heat pump in your home?
In the following guide, we’ll explain exactly what hybrid heat pumps are, how they work and the running costs, the benefits they offer, as well as potential disadvantages.
But, without further ado, let’s explain what a hybrid heating system is…
Ready to make your home more energy-efficient and cut down on your heating bills? Get a heat pump quote today from our trusted partners at Heat Geek here.
What is a Hybrid Heating System?
Essentially, a hybrid heating system is comprised of a traditional heating boiler, powered by natural gas, oil or LPG combined with a renewable technology such as an air or ground source heat pump.
Both of these products are harmonised by either a mechanical or electrical control centre (usually a wall-mounted box about a third of the size of a boiler).
Or in the case of Alpha Innovations' solution, a smart thermostat is linked to a powerful web server.
Hybrid systems are very popular in mainland Europe and demand from the UK market is growing.
This is largely driven by consumers' desire to reduce their carbon footprint and fossil fuel dependence without the disruption and cost of installing a traditional air source heat pump solution.
PS you can read our complete review of the Alpha E-Tec Hybrid Boiler here.
Alongside some of the world’s largest thermomechanical manufacturers such as Worcester Bosch, Alpha Innovation and Viessmann - the UK government is exploring how to further support the rollout of hybrid heat pumps.
An update on the consultation is expected to be released on 21st March 2023.
Check out the video below to see a hybrid heat pump installation case study in the UK:
How does a hybrid heat pump system work?
The general design concept for all hybrid heat pump systems is broadly similar, comprising three main components:
A renewable technology which in 95% of applications would be an ultra-efficient external air source heat pump
A traditional gas boiler - which can be either a combi, regular or system
A mechanical or electronic control unit to manage the system's efficiency
Each component has a job to do in balancing the performance and efficiency of the system.
The air source heat pump usually has a smaller output (3-6kw) than a traditional setup (6-12kw).
The purpose of the air source heat pump is to produce as much heating energy at the highest possible efficiency return.
Thanks to the smaller size of the unit and the lower flow temperatures required, this would be around 400%, meaning that for every 1kw of energy used, 4kw of energy is returned.
This renewable, high-efficiency heat is then circulated around the property to heat radiators or underfloor heating to an expected flow temperature of around 40-50 degrees.
The boiler unit operates much like an existing gas or oil boiler. They burn the fuel to produce heat for heating or in the case of a combi boiler, heating and domestic hot water.
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Modern efficient gas boilers can be up to 95% efficient. And thanks to the high calorific value of fossil fuels, boilers are usually rated between 20-35kw for their peak power outputs.
Heat-up times are rapid and they’re also versatile in their power production meaning that they can turn down (modulate) usually to 3-4kw when demand is lower.
The control unit is a piece of hardware or in the case of the Alpha Hybrid Heat Pump a smart controller, linked to a powerful server-based algorithm.
The unit's purpose is to manage energy production from both the heat pump and the boiler to suit the requirement of home heating needs, ensuring that the most efficient settings are used.
For the control unit to be effective, an external temperature probe is required, usually, these are built into the heat pump.
The sensor reports the current external ambient temperature back to the control unit, enabling the desired flow temperature of the system to be automatically adjusted (the lower the temp, the higher the efficiency).
This process is managed by something called a heat curve.
A heating curve is a delta (disparity) between the outside temperature, the current internal temperature, the desired temperature and the system flow temperature.
The lower the flow temperature a system can operate, the less fuel is required with the net result being a higher efficiency value.
There’s currently lots of noise from industry advocates about turning down your boiler flow temperature to save energy.
This is solid advice and a great place to start however, for your home to be comfortable during varying temperature cycles you may need to adjust this frequently, something that isn’t really that practical.
Having an external weather probe mitigates this as the process becomes automated using complex algorithms.
More heat pump guides:
Why do I need the gas boiler if the heat pump can heat my home?
The gas boiler is there to support the heat pump in times of peak demand or very cold weather.
For combi systems, it's also there to produce demand for high-temperature domestic hot water for showers, taps and baths.
Something that a traditional air source heat pump cannot do without storing hot water in a cylinder.
This may also struggle to be heated to a suitable temperature (65°c) without dropping its efficiency to below an economically viable value.
Various manufacturer studies have shown that in a hybrid heat pump setting, up to 75% of the space heating is provided by the heat pump.
The gas boiler is only employed to step in when rapid heat-up times are required or when the external temperature drops below around 8°c.
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This is because a heat pump becomes less effective when the ambient air temperatures it needs to convert to heat become lower and therefore require more energy for conversion.
The same challenge presents itself when the unit is required to produce a much higher flow temperature for rapid heat-up requirements.
The management of the various component operations is executed by the control unit, in combination with the external weather probe.
You’ll also need your gas or oil boiler to produce hot water if you have a combi boiler.
If your system doesn’t feature, or rather isn’t suitable for a combi boiler then the alternative to this is to site a water storage cylinder within the property, combined with an electric immersion to reach the required 65°c.
Learn all about hybrid heat pump/boilers in our video tutorial below:
What efficiency can I expect with a Hybrid Heat Pump Boiler?
As we covered earlier in this article, the standalone efficiency of a standard heat pump (in optimal setting) is rated between 300% to 400%.
The size of the hybrid heat pump unit helps this overall efficiency improve by up to 420% thanks to its lower-rated output.
If the central heating (space heating) in your property was solely powered by the heat pump, achieving a flow temp of around 40°c, then your overall system efficiency would effectively be around 400%.
This optimal configuration would be achieved during milder periods when the temperature drops below certain thresholds.
In these situations, the heat pump either needs to increase flow temperature (increasing the heat supply to the radiators) with a drop in efficiency.
Or with a hybrid system, it can maintain the optimal flow rate of 40°c, boosted by the increased flow temperature by the gas boiler.
Once the system is up to temperature, the boiler switches off and regular service resumes.
According to Alpha Innovation which has installed close to 750,000 hybrid systems, data shows that typically:
A combined cycle across all seasons returns an overall efficiency of 130% at a flow temperature of 55°c and up to 160% at a flow temperature of 35°c.
Translated, this means that there are savings of up to 60% for gas usage for the space heating demands of a typical home.
Given that space heating emissions for the UK are estimated at over 6000 tonnes of Co2 per year, if everyone installed a hybrid heat pump system in their home it could make a huge impact.
In fact, by replacing a standalone gas boiler with a hybrid system, the UK could cut heating emissions by up to 60000 tonnes of Co2, the equivalent of taking 20,000 cars off the road each year.
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Are they suitable for all property types?
Unlike a traditional heat pump application, hybrid systems are suitable for pretty much any house type. The only requirement is that there is enough space to house the internal and external units.
There are no requirements to install increased surface area radiators, or a water cylinder if you don’t already have one.
You also don’t need planning permission or clearance from your local electrical network due to the low power rating of the heat pump.
It is worth bearing in mind that systems that can run at lower temperatures will return high efficiencies and therefore lower running costs.
This can be achieved by improving insulation, installing draught-proofing and upgrading radiators to modern, high-output units.
These measures are usually low cost compared with the requirements to install a traditional heat pump.
Are hybrid heat pumps noisy?
No, due to the compact size, smaller fans and relatively lower outputs than standard heat pumps, they’re almost silent.
Something like the Alpha Etec 33HB’s external unit is rated as low as 35db.
Hybrid Heat Pump Running Costs UK
Will a hybrid heat pump save you money?
Yes, the design intention and operation of a hybrid heat pump set-up essentially guarantee to ensure that you’re home is being heated by the most efficient configuration.
Either ultra-high efficient renewable energy or with fossil fuel assistance.
Smart systems like the Alpha Etec 33HB allow the user to enter their current electricity and gas tariff rates.
Using this data, Alpha’s powerful server technology instructs the control unit to operate in the ultimate efficient configuration.
For example, if you assume a customer was paying 10p/kw for gas and 30p/kw for electricity (usually, electricity is charged at about 3 x the cost of gas per unit), you could assume the following:
Scenario 1 - The outside temperature is 15°c and the current internal temperature is 18’c and the desired set temperature is 21°c.
The system needs to warm the property by 3°c to achieve the target.
Given the mild external temperature, the heat losses will be reduced and the system would be able to flow at a lower temp to achieve the customer's target set temperature.
The system knows that the heat pump can achieve this without the aid of the gas boiler using approx 4kw, at a flow temperature of 40°c and returning an efficiency of 400%.
This means the target temperature can be achieved for 30p (7.5p/kw x 4kw).
Scenario 2 – The outside temperature is 5°c, the current internal temperature is 15’c and the target temperature is 21°c.
The system needs to heat the property by 7°c and it's likely that heat losses due to the cold external temperature will be higher.
The system knows the flow temp needs to be 55°c to achieve the desired set temperature and uses approximately 20kw.
Doing this would drop the efficiency rating of the heat pump to 200% without the aid of the gas boiler (as with a traditional heat pump setup) this would cost £3 (20 x 15p/kw).
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The system, therefore, decides to use the 10kw from the heat pump up to a flow temp of 40°c at a cost of 75p (10 x 7.5p/kw) then use the gas boiler to increase the temperature to the required 55’c.
To achieve this, the boiler will use an additional 10kw of energy at 10p/kw, bringing the combined cost to £1.70.
If the property only had a gas boiler, 20kw would still be required however all of this power would come from the boiler, costing £2 (20 X 10p/kw).
Is there a specific type of hybrid boiler system I need?
Some solutions are designed to be retrofitted onto your existing system, using various components from different manufacturers.
Some are “whole box” solutions where all the components are from one manufacturer and designed from the ground up.
Much like the bicycle industry offers complete E-bike solutions and retrofits electric motor/battery conversion kits.
The motor industry also rolled out the majority of electric cars this way too.
In fact, most manufacturers converted combustion engine cars to incorporate hybrid battery solutions, then later developed purpose-built hybrid cars and EVs.
Generally, a purpose-built solution such as the Alpha Etec HB 33 is favourable over retrofit kits.
This is mainly due to factors such as:
Compatibility issues with older boilers
Diagnosing product failures (i.e which manufacturer is liable for the repair)
Maintenance – engineers would need to be trained on various manufactures products
Retrofit systems can cost more to buy as they usually need additional components to work
Hybrid Heat Pump Costs
Material prices vary between manufacturers.
Full kit costs including the heat pump, indoor control unit, pipework, insulation, water treatment and fittings start from around £5,000 and can cost as much as £8,000.
Labour costs are very specific to the individual or company quoting, generally speaking, an installation would take 2 or 3 days to complete and would require two installers (the units can weigh over 100kg).
You’d expect to pay between £1500-£3000 for labour. Around another £500 should be budgeted for any electrical connections.
Purpose-built solutions which include everything above but also a new high-efficiency boiler usually cost about the same as all the components come from one manufacturer and not from multiple suppliers.
What are the benefits of installing a hybrid heat pump?
Hybrid heat pumps offer many positive benefits to consumers and the environment.
These include the following:
Reduced carbon emissions by up to 60% for the space heating element of gas boiler emissions.
Reduced energy costs thanks to system efficiency
Reduced dependence on units of electricity as the heat pump can work up to 420% efficiency.
Piece of mind for consumers who are worried about the cost of stand-alone heat pumps.
Back up heating in the event of a component failure. If either the heat pump or the boiler fails, heat is still available from the opposing component until a repair visit is carried out.
Unlike traditional heat pumps, hybrid heat pumps are suitable for most applications where replacing pipework or significantly increasing radiator sizes is not an option or is within budget.
Disadvantages of Hybrid Heat Pumps in the UK
Whilst hybrid heat pump boilers offer significant advances in meeting our decarbonisation goals, there are some drawbacks you should be aware of.
Currently, in England, hybrid heat pumps are not included in the government's boiler upgrade scheme (BUS) where consumers can claim up to £6000 towards the cost of installing a traditional heat pump.
Hybrid heat pumps don’t currently qualify for zero rated vat treatment
There is still a requirement to site an external unit, something which UK consumers aren’t familiar with (you can buy a fancy cover)
Installation costs can be 2 or three times the cost of installing a traditional gas boiler – get an online quote for a traditional gas boiler or a hybrid heat pump boiler here in 60 seconds.
Whilst your gas usage will drop by up to 60%, you will still have to buy some electricity to power the heat pump, thankfully, the heat pump will convert every pound you buy into £4 worth of heat in the optimal setting.
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