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Heat Pump FAQs

What is a heat pump?

Heat pumps are often described as being like a fridge in reverse. Although this doesn’t make their operation entirely obvious, it’s not far off! Heat pumps use the same refrigerant cycle as a fridge to move heat from one place to another. Despite the common misconception, fridges don’t work by filling the compartment with cold air – instead, they move the warm air out. A heat pump works in a similar way, but instead of moving warm air out, it moves warm air in. A heat pump extracts warmth from the outside air before concentrating it and transferring it into your home to provide heating and hot water.

How do heat pumps work?

A Vaillant heat pumpAt its simplest, heat pumps transfer outside energy into heat for your heating and hot water system. Some heat pumps extract energy from the air, and these are known as ‘air source heat pumps’. Another type of heat pump extracts energy from the ground, and these are known as ‘ground source heat pumps’. As their name suggests, they pump heat, taking energy (from the air or the ground) from a low temperature source and forcing that heat to a higher temperature for our heating.

Do heat pumps work as well as boilers?

As soon as any new initiative is launched, you can expect some scare mongering in the news and social media! But heat pumps (when properly fitted by an expert) are just as good, and in many ways better, than a conventional boiler. Despite what you might have read online, properly installed heat pumps are more than capable of keeping your home warm on the coldest of days.

It’s understandable that people are concerned about how a device is going to absorb heat from the ground when it’s snowy out – but there’s no need to worry! In the UK, the temperature of the ground doesn’t usually fall below 10 °C. Although you might think that’s a bit nippy, there’s still heat in the ground for the taking. Air source heat pumps will use ambient heat. 

Do heat pumps work when it’s cold?

Yes! Because of the way a heat pumps’ refrigeration cycle works, heat can be extracted out of the air at very low temperatures- even negative temperatures. Back to the fridge analogy, if you touch the grill on the back of a fridge, it feels warm. But it’s cold inside the fridge, and nothing warm has been put in it. This is similar to a heat pump, A heat pump will still operate to get your radiators and hot water to temperature, right the way down to -25c!*

What is an Air Source Heat Pump (ASHP)?

A Vaillant heat pump.An air source heat pump works by using a fan to draw in air from the outside and absorbing the heat into a liquid refrigerant. Using electricity, the heat pump compresses the liquid to increase its temperature. It then condenses back into a liquid to release its stored heat. Heat is sent to your radiators or is stored in a cylinder to provide you with hot water when you need it. Air source heat pumps are easier to install than a ground source heat pumps because they don’t need the network of underground pipes that a ground source heat pump requires.

What is a Ground Source Heat Pump (GSHP)?

Ground source heat pumps collect heat from the ground through a network of water pipes buried underground. A mixture of water and anti-freeze is pumped around the network of pipes and absorbs the naturally occurring heat in the ground. This heat is then transferred to a liquid refrigerant inside the heat pump. At this point, the process is the same as with the air source heat pump – electricity is used to compress the liquid refrigerant to increase its temperature. It then condenses back into a liquid to release its stored heat. Heat is sent to your radiators or is stored in a cylinder to provide you with hot water when you need it. Ground source heat pumps are more expensive than air source, because of the network of underground pipes that need to be installed. But they do tend to be more efficient.

How efficient are heat pumps?

One of the biggest advantages of heat pumps is that they’re incredibly energy efficient – which is referred to as the Coefficient of Performance (CoP). The CoP is the amount of heat generated for every kilowatt of electricity used. An air source heat pump can convert each kilowatt (kW) of electricity into 3-4 kW of heat. This means that they’re between 300%-400% efficient! This is pretty impressive when you compare it to a modern gas boiler with an energy efficiency of about 92%!

Why are heat pumps so efficient?

Heat pumps manage achieve their impressive energy efficiencies because they transfer heat rather than generate it. Because your boiler has to generate heat by burning fuel (usually gas), there will always be some energy wasted in the heating process.

Are heat pumps expensive to run?

No – a heat pump that has been installed on a well-designed system won’t be expensive to run. But if you’re in the market for a new heat pump, it’s vital that you contact an expert. As you might expect, designing an efficient heat pump system is more complex than designing a system for a gas boiler. And poor design will lead to high bills.

This is where The Heating People really excel. We are proud to be Heat Geek Elite designers, working with the Heat Geek assured installation scheme. We design and install the most efficient heating systems for homes in the North West. When we design a system for you, we will advise on the projected efficiency of the system, which with a bit of information about your gas and electric pricing, can show you a projected running cost against that of a gas boiler. You have all the facts prior to installation.

What is the Heat Geek Assured Heat Pump Installation Service?

The Heat Geek Assured service means that you can be sure that you have an expert designing your heat pump system. Heat Geek personally vet and train Heat Geek installers to the highest industry standards. Heat Geek engineers have undergone the best system design training available and are heavily involved in ongoing peer to peer training. Heat Geeks know the very latest technology, methods and design practices available. This gives you the peace of mind that your installation is not only working but working to the maximum efficiency. The Heating People are proud to be Heat Geek Elite installers, the highest accolade there is in the industry!

What does it cost to install a heat pump?

An engineer installing a heat pump.The cost of installing heat pumps varies depending on what system is being installed. As a guide, the cost of an ASHP will be around £15-£20,000 before any government grants are applied. Whilst installing a heat pump isn’t cheap, it’s important that you weigh that against the pay back you’ll get on your energy bills – not to mention the environmental benefits! And you may be able to get some financial help too. You can apply for funding for a heat pump under the Renewable Heat Incentive, and there are also grants of £5,000 through the new Boiler Upgrade Scheme.

What financial help is there to install a heat pump?

A heat pump installation by The Heating People.The government has announced it will be giving households grants towards the cost of installing heat pumps, to try and achieve its target of installing 600,000 per year by 2028. Under the new ‘Boiler Upgrade Scheme’ grants of £5,000 will be made available to help households to afford to install air source heat pumps. There will be grants of up to £6,000 available towards the cost of installing a ground source heat pump.The government has set aside £450 million for the grants, with the total money allocated enough to cover 90,000 homes.

How do heat pumps save money on energy bills?

Because heat pumps are so efficient, they can save you money on your energy bills (certainly once the price of electricity comes down!) To illustrate this, think about a modern boiler with 92% energy efficiency. This boiler will use 92% of the supplied energy for heating your home but the remaining 8% of energy will be lost in the process of generating heat. So, this means that for every £1 you spend on heating your home, this boiler is wasting 8p!

Now think about a heat pump with 300% energy efficiency. Not only is this heat pump not wasting energy, but it’s also giving out more than you put in. Hopefully it’s now easy to see what a positive impact a heat pump can have on your energy bills! However, electricity prices are currently very high, particularly in comparison to gas. But it’s important to remember that heat pumps are so efficient, they can convert a unit of electrical energy into 2-4 times as much heat energy.

Will a heat pump reduce my carbon footprint?

Yes! The reason that the government has such ambitious targets for the installation of heat pumps, is because they’re much more environmentally friendly than gas boilers. According to EDF Energy, installing a heat pump could cut your carbon emissions by more than 23 tonnes of CO2 over 10 years. That’s the same as 30 return plane flights between Heathrow and Madrid! Heat pumps use some electricity to run. But if you’re able to power them with electricity from renewable sources, such as solar power, they are completely carbon neutral.

Are heat pumps 100% carbon neutral?

Heat pumps are much more eco-friendly than traditional gas boilers, but they are not 100% carbon neutral. This is because they use a small amount of electricity to run. If you want to be completely carbon neutral, you’ll need to run your heat pump on electricity from a renewable source such as solar power.

What is involved in getting a new heat pump with The Heating People?

A heat pump installation by The Heating PeopleIf you’re thinking about getting a heat pump, but are concerned about what’s involved – don’t worry, The Heating People are here to help! We are heating specialists who take the hassle out of high efficiency system design. Here’s what to expect from the process with an installation from us…

Step 1: Contact us

To get started, contact one of our friendly team at The Heating People. We’ll ask you a few simple questions about you and your property, and get you booked in for a discovery call with Heat Geek Elite installer, Liam. You can contact us in the following ways:

  • By phone on: 0151 7926245;
  • By email at: hello@theheatingpeople.co.uk;
  • through the contact form on our website.

Step 2: Discovery call

Katie installing a heat pump for The Heating People.We will call you as arranged on a date and time of your choosing, for a ‘discovery call’. During this call, we will take some more detailed information about your home and what you’re hoping to achieve from your heat pump. We will advise you on the suitability of your home and advise on any pitfalls. We can even give you an estimated installation cost on this call. If you’re happy, and we’re happy at the end of the call, we book an initial survey with you to do a more detailed assessment to provide a fixed price quotation.

Step 3: Technical survey

An engineer installing an aroTHERM heat pump.During the technical survey, we will visit your home and carry out a full heat loss assessment as well as an assessment of your existing heating system. This will allow us to design a heating system that is suitable to heat your home and to provide you with the lowest flow temperatures possible which will increase the efficiency of your system.

Step 4: Proposal

Following the technical visit, we will provide you with a proposal for the installation of your heat pump. We will also provide you with a report containing all of the technical information we gathered and the calculations completed on site. When you are happy to proceed with the work, we will book you in for your installation date.

Step 5: Installation

A heat pump installation by The Heating PeopleOn your installation day, your engineer will discuss the planned work, to ensure that everyone is happy with the plans. They will explain where they will need access to, and for how long, so that you can plan your day. Your engineer will put down floor coverings in all work areas and transit routes, so that you can rest assured that your home will be protected from any debris. Your engineer will decommission your old system, and will set to work installing your new heat pump. Your engineer will then set up your new system. They will complete a handover with you when all the work is complete. This ensures that you are as informed as possible on how to operate the heat pump, how to use all the controls, and how to get the best efficiency from your system.

The follow up

We take pride in our work, and The Heating People will come back and check that everything is working as designed after your heat pump has been operating in winter conditions.

Why do The Heating People install Vaillant aroTHERM heat pumps?

A heat pump installation by The Heating People.The Heating People are proud to be Vaillant Advance Installers because Vaillant has a growing focus on products and systems that use renewable energy. We share their motto of: ‘thinking ahead’ and only use products with high energy efficiency ratings and low carbon emissions. Many Vaillant products are based around the use of heat pumps taking heat from ambient air and the earth. Vaillant is expanding its UK manufacturing facility in Derbyshire to produce its aroTHERM plus heat pumps from 2022, and we really rate this heat pump!

The aroTHERM plus air-to-water heat pump is one of our personal favourites because it is environmentally friendly and future-proof:

  • Future-proof thanks to the most cutting-edge heat pump technology with natural refrigerant, reducing your carbon footprint;
  • High energy efficiency class;
  • Very quiet operation – can even be used in densely built-up terraced housing estates;
  • Outstanding quality and durability.

As Vaillant Advance Installers, we can offer a range of warranties of up to 7 years on parts and labour.

What controls should I use with my new heat pump?

Vaillant sensoCOMFORTWhen installing a Vaillant aroTHERM heat pump, we use Vaillant’s sensoCOMFORT controls. The sensoCOMFORT is Vaillant’s new control for multi-zone heating systems. It has been designed to be simple to install and use, and operates with Vaillant’s eBUS protocol. This ensures all components of the system can easily communicate with each other to provide optimum system performance. It’s perfect for multi-zone gas-fuelled systems, and hybrid or renewable installations.

The sensoCOMFORT comes with an outdoor sensor, providing weather compensation that automatically adjusts the flow rate from the boiler for ultimate efficiency. Load compensation comes as standard.

Are gas boilers being banned and replaced with heat pumps?

A hydrogen ready boiler and heat pump.You don’t need to worry about a ‘ban’ as such. But, the government has announced an ambition to phase out the installation of new gas boilers beyond 2035, in favour of ‘greener’ alternatives. This won’t impact your current boiler, and you can still replace your current one until 2035. After that, we’re likely to see a combination of both hydrogen boilers and heat pumps being used to heat our homes.

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Understanding boiler specifications

When you’re shopping for a new boiler, it can be hard to know where to start.

If you’ve taken your boiler search online, you were probably surprised by how much choice there is!

Although boilers essentially do the same job of keeping your home warm, and your baths hot, there’s a vast array of different makes and models to choose from.

And although boilers might all look very similar (to the untrained eye!) – don’t be fooled – not all boilers are created equal!

To find the most cost-effective and efficient way to heat your home, you need to make an informed decision, not one based solely on aesthetics or price.

This is where boiler specifications come in. The technical information found in a boiler specification is important. It will help you to find the most cost-effective and efficient way to heat your home.

But what does it all mean?!

The facts, figures, and general jargon contained in a boiler specification can be confusing. So, we’ve put together this handy guide to help you  understand what you’re looking at.

The three types of boilers

Diagram of the 3 types of boiler.Before we get into the nitty gritty, let’s start with the types of boilers that are available.

There are three main types of boilers for you to choose from: combi boilers; system boilers; and heat-only boilers. Since they all work differently, you’ll come across slightly different boiler specifications for each.

We’ve dedicated entire blogs to each of these boiler types, but we’ll summarise the key differences again here:

Combi boilers

Combination or ‘combi’ boiler is the most common type of domestic boiler in the UK. They provide a combination (hence the name!) of heating and hot water from one compact unit. They don’t require any external tanks or cylinders because they heat water instantaneously on demand.

Read their pros and cons here.

Heat-only boilers

Heat-only boilers, also known as traditional or conventional boilers, are usually fitted to an open-vented system, which require cold water and feed and expansion tanks in the loft. Since they store hot water in a cylinder, they can meet high demand for hot water, and are also perfect for homes with low mains pressure.

Read their pros and cons here.

System boilers

System boilers operate on a sealed system. So they don’t have tanks in the loft, but they do store hot water in a cylinder. As with heat-only boilers, this makes them well suited to homes with a high demand for water.

Read their pros and cons here.

Understanding boiler specifications

Now let’s look at some of the key terms you may come across in a boiler specification:

Understanding boiler specifications: DHW

DHW stands for Domestic Hot Water. This refers to the water that comes from a hot tap or is stored in a hot water cylinder (with a heat-only or system boiler).

With a combi boiler, the central heating and DHW are combined into one appliance. When you turn on a hot tap, a combi boiler prioritises the DHW, and stops pumping water to the heating circuit.

Understanding boiler specifications: CH output

CH stands for central heating. As well as providing your hot water for your taps and showers, your boiler also heats your home. It does this by heating water which is pumped around your radiators, before returning to the boiler for reheating.

Understanding boiler specifications: Boiler efficiency (ErP)

ErP stands for Energy-Related Products. It is a rating system which rates an appliance’s energy efficiency from A-G, with A-rated products being the most efficient.

You’ll also see this rating system on other household appliances, such as your fridge, washing machine and oven.

Combi boilers have two ErP ratings, one for heating your home, and one for heating water for your hot taps. This is because combi boilers power your central heating and hot water independently.

If you have a heat-only or a system boiler, you’ll just have one ErP rating for heating.

The purpose of ErP ratings

The purpose of the ErP rating system is to ensure that consumers are aware of how energy efficient (or not!) their appliances are.

In turn, this helps governments to reduce carbon emissions, while helping homeowners to reduce their energy bills.

All new boilers must be 92% efficient (or ‘A-Rated’ on the ErP label).

If you’re upgrading from a boiler with a lower efficiency rating, you’ll save money on your energy bills each year because efficient boilers waste less energy.

To find out more about this, you should check out our related blogs: What is an efficient boiler, and why should I want one? and What is Boiler Plus?

According to the Energy Saving Trust, if you swap a D-rated gas boiler to an A-rated condensing gas boiler, you could save around £170 a year on your central heating bill. The savings will be even greater if swapping from G-rated boiler to an A-rated one.

And, with gas prices soaring, the savings are likely to be substantially higher than that now!

Understanding boiler specifications: SEDBUK

Although SEDBUK was effectively replaced by the Energy related Products (ErP) directive in 2015, you’ll often still see SEDBUK appearing on boiler specifications.

SEDBUK stands for: ‘Seasonal Efficiency of Domestic Boilers in the UK’. SEDBUK was a UK initiative which provided a basis for fair comparison of the energy efficiency of different models of boilers.

The SEDBUK scale labelled boilers with a letter from A – G, with A being the most efficient boilers.

On the SEDBUK scale, boilers classed as A and B were highly efficient, whilst bands C to G were classed as having ‘standard efficiency’.

Understanding boiler specifications: Boiler power (kWs)

This can be confusing, because you’re more likely to have heard of people referring to boiler power as boiler ‘size’.

But when we’re talking about a boiler’s ‘size’, we’re not talking about its physical dimensions, but rather, its power.

Boiler power is measured in kilowatts (kW). The more power the boiler can generate in kWs, the bigger it is in terms of ‘size’.

At its simplest, a more powerful (or ‘bigger’) boiler will be able to heat more radiators and provide more hot water. But this doesn’t mean that bigger is always better!

Many people fall into the trap of choosing a boiler that’s too big (or too powerful) for their needs, thinking that it’s better to have too much power, than too little.

The problem with oversizing boilers

But too little power isn’t good either, because your boiler will struggle to provide enough heating and hot water for your needs.

So, you need to choose a boiler that’s power output can precisely meet your requirements. Whilst a lot of online ‘calculators’ say you can do this by counting your radiators – and this really grinds our gears! – this isn’t true.

The accurate way to size a boiler (and industry standard under Part L of the Energy Efficiency Regulations) is through a heat-loss calculation.

Rest assured, that The Heating People conduct heat-loss calculations as standard as part of your free survey. We will calculate and recommend the correct size of boiler for your home.

But so that you can understand this better, let’s look at what the Kw numbers mean…

What the numbers on the specification mean…

A diagram showing boiler input and output.When looking at a boiler specification, you might see two numbers by boiler power. One is the power input; the other is power output.

Both are measured in kW and, depending on the boiler type, can refer to just your central heating (CH) or both your heating and your domestic hot water (DHW).

Input refers to how much energy goes into the boiler to make it work, and it’ll be reflected in your energy bill.

Output tells you how much of that energy is converted into heat for your radiators and hot water for your taps. This number will always be lower than the input because no boiler is 100% efficient. Some energy will be lost in the heating process.

What is a kW?

A kilowatt is a measure of power, equal to 1,000 watts. Watts measure power generated per second.

So, a boiler with a maximum output of 30kW will produce 30,000 joules of energy per second when in operation. This energy is used to heat your home.

The higher the kW rating of a boiler, the more powerful it is, and the more radiators and taps it can supply at one time.

Why do combi boilers have higher power outputs?

You may notice that combi boilers often have larger power outputs than heat-only or system boilers. This is because combi boilers operate differently, by heating water instantly on demand.

Heat-only and system boilers don’t have to heat water instantly, they can heat it up more slowly because they store it in a cylinder for later use.

What is a kilowatt-hour (kWh)?

You might have come across kilowatt-hours on your energy bill, and be wondering how this differs from a kilowatt.

A kilowatt (kW) is a measurement of power. A kilowatt hour (kWh) measures how much energy an appliance could use if it was on for one hour.

For example, a 30 kW boiler needs 30 kWh of energy for each hour that it’s heating your home. So, if it’s operating for 3 hours then it will use 90 kWh of energy to do its job.

Understanding boiler specifications: Boiler modulation

A diagram showing boiler modulation.You’ll see some specifications talking about boiler modulation. But unless you’re in the heating industry, this probably won’t mean much to you!

So, what does boiler modulation mean, and why is it important?

Boiler modulation refers to the ability of the boiler to automatically reduce its output to suit the demand for heat.

Let’s say you only need 15 kw of heat for your home for the next couple of hours. But you have a 30kw boiler.

Instead of your boiler outputting 30kw and then cycling on and off, your boiler would reduce its output by turning down its flame by 50%.

The advantage to this is that it lowers the amount of gas being used by your boiler. This saves energy, and therefore money on your energy bills.

It also creates a more consistent environment and helps to prolong the life of your boiler by preventing on/off cycling.

What are modulation ratios?

Diagram showing boiler modulation ratios.Boiler manufacturers state the ability of a boiler to modulate as a modulation ratio.

The fraction refers to a boiler’s minimum output in relation to its maximum output. The wider the modulation range, the better the ratio.

Let’s look at some examples to help explain this:

Boiler A

Boiler A has a maximum output of 30kW and has a 5:1 ratio. This means that the maximum power it can output to heat your home is 30kW, and it can modulate this down to 6kW.

Boiler B

Boiler B has a maximum power output of 30kW and a 10:1 ratio. This means that the maximum power it can output to your home is 30kW, and it can modulate this down to 3 kW.

Boiler C

Boiler C has a maximum output of 30kW and an extremely impressive 17:1 ratio. This means that the maximum power it can output to your home is 30kW, and it can modulate this down to 1.7 kW.

So, which of the boilers in our examples is the most efficient?

Boiler C is the most efficient boiler because it can modulate its output from 30kW to 1.7kW with a total of 17 different heat outputs.

Lower power output means less fuel burned, and more money saved on your bills.

To put this in perspective… If you only need a very small increase in heat, Boiler A would fire at 6Kw, but Boiler C would fire at a lower (and more efficient) 1.7Kw.

A non-modulating boiler would fire at its maximum output of 30Kw regardless of the heat demand, consuming unnecessary energy and overheating the home.

Another advantage is that there will be less boiler cycling, and so there will be a lower level of stress placed upon the boiler, potentially extending its lifespan.

If you’re interested in boiler modulation, you might also be interested in our related article on the benefits of low temperature heating.

Understanding boiler specifications: Water flow rate

An important feature specific to combi boilers, is the water flow rate.

Measured in litres per minute, the water flow rate shows how much hot water your boiler can send to your taps in one minute.

Sometimes the output specifications for a boiler will state the maximum flow rate that the boiler can provide at a specific temperature. For example, you might see a flow rate of 15 l/min at a temperature of 40 degrees centigrade.

Generally, the more taps and showers you have in your home, the higher water flow rate you need.

However, you could be wasting your money if you choose the boiler with the maximum flow rate, if the mains supply to your house is lower than the flow rate of the boiler.

If you were to buy a boiler with a flow rate of 12 litres per minute (l/min), but the flow rate of your mains water is only 8l/min, your boiler won’t be able to reach 12 l/min.

If your mains water isn’t coming in fast, it won’t come out of your tap fast either!

Understanding boiler specifications: Pressure

Technical specifications for boilers often include figures related to gas and water pressure, and are typically measured in bars.

‘Minimum inlet pressure’ describes the lowest pressure required for gas entering the boiler in order for your boiler to operate safely and efficiently.

There also might be a minimum and maximum rate for water pressure.

Conclusion

A boiler is a big investment, and you’ll want to get it right. After all, it’s going to be tasked with keeping you and your family warm and comfortable for at least the next decade!

So, we hope that reading this guide has left you feeling better equipped to research your new boiler.

But if you still feel overwhelmed, don’t worry, The Heating People are here to help!  Contact one of our friendly team to set up a free, no obligation appointment with one of our heating specialists.

They’ll visit your home, complete a survey, then talk through your options and answer any questions.

Useful links:

Heat Geek: What is boiler modulation?