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The Realities Of Heat Pumps: Can They Replace Gas Boilers?

Can a heat pump replace gas boilers? That's the question many commercial and residential clients ask as the search for viable, alternative energy resources continues. The embers of the ongoing debate have been stoked by the government announcing it favours air source and ground source heat pumps as the eventual successors to boiler gas as part of its boiler upgrade scheme.


This blog aims to show the realities of heat pumps, how they compare to gas boilers and whether they will indeed replace gas boilers in the future.


We will explore how the two systems operate, their efficiency, eco-friendliness, and how much they cost to run and install.


Heat Pumps v Gas Boilers - Main Differences


Let's start the comparison by looking at how heat pumps and gas boilers work.


Firstly, boilers can heat cold water reasonably quickly, which is one of the main reasons they have proved so popular. They can heat radiators and, therefore, large open spaces - like offices or warehouses - to high temperatures in no time.


A boiler system is often designed to run at flow temperatures of around 70°C (this is the temperature of water sent round to your radiators). The water returns to the boiler after travelling around your radiators (called 'the return'), usually between 10-20°C cooler.


By contrast, heat pumps produce heat more slowly and at lower temperatures.


They ideally want to have an average temperature of roughly 37.5°C and a temperature difference of only 5°C. To be as effective, the radiators they feed in to need to have a much larger surface area. So rather than pumping water into traditional wall-mounted fixtures, they are probably best suited for underfloor heating systems.


When asking yourself whether to swap a gas boiler for a heat pump, you will need to be aware that existing radiators and pipework, as well as your existing source, may need to be updated.


Heat Pumps vs Gas Boilers - Efficiency


Which is more efficient: a gas boiler or a heat pump?


Natural gas boilers have a heat exchanger within the gas combustion chamber. Water passes through this exchanger and absorbs heat from the burning gas. Because it is so efficient, around 90% of the energy is absorbed into the water.


Furthermore, because much heat is created, water vapour condenses - hence the system being referred to as a condensing boiler.


The efficiency of a heat pump is known as the Coefficient of Performance (CoP). This is the ratio of the amount of electricity used to the amount of heat produced for the home.


For example, if the heat pump uses 1kWH of electricity and produces 3 kWh of heat, the CoP is 3 (or 300%) efficiency.


A wide range of contributing factors and many formulae are used to deliver and calculate this efficiency. So it is essential to understand precisely what you should expect from each system when comparing.


Heat Pumps vs Gas Boilers - Costs



A pound coin on a white background


This is ultimately what it boils down to: how much do either of the heating systems cost to set up and run?


Heat pumps are certainly more expensive to buy.


Currently, if you are looking at installing an air source heat pump, you can expect to pay between £8000 and £16000. It can even be as much as £28,000 if you need to upgrade radiators and replace pipework.


For ground source heat pumps, you are looking at around £14,000 to £25,000 for an installation and perhaps even more if you need a large borehole collector.


There are many variations of a boiler, with prices ranging from £500 to £2,500 depending on your chosen make and model. The installation will usually cost more.

But what about running costs?


As previously discussed, heat pumps run on electricity, and boilers burn gas. As a result, a cost comparison will need to consider the unit cost of each fuel.


Electricity costs between 12p and 24p per kWh, depending on your tariff. Alternatively, natural gas is between 3 and 5p.


This means that, in terms of financial cost, the heat pump would need a CoP between 3 and 5 (an efficiency of between 300 and 500%) to be comparable.


As the cost of gas and electricity changes, so will this calculation. However, there is one thing you can be sure of. The cost of energy will continue to rise, and the gap between the price between electricity and gas will close.


In the current climate, switching gas to heat pumps can be pretty expensive. Still, as the energy cost gap closes, the numbers will eventually become more favourable for heat pumps.


The fact that heat pumps save you money on energy bills and last twice as long as a commercial boiler means that over time, they will benefit you financially.


Heat Pumps vs Gas Boilers – Space Required


In order to further explain the realities of heat pumps vs boilers, we should also consider the amount of space both of them require.


Firstly, many of us will already be familiar with the size of a standard gas boiler.


However, heat pumps require alternative equipment for office set-ups.


There are two main types of heat pumps:


- air source

- ground source.


Air source heat pumps collect heat from ambient air whilst ground pumps receive heat from the ground.


Air source heat pumps usually have a large box measuring 1200mm by 1000m outside your building with a fan and compressor inside. This box absorbs heat from the air as the fan draws it through. Additionally, the outside unit needs 2 metres of space in front of it.


To install these, you will also need space inside the property for a hot water cylinder, control box and potentially a second buffer tank, which is about a third of the size of a standard tall hot water cylinder.


Ground source heat pumps, on the other hand, can be installed virtually anywhere. Open-loop systems will need access to a water source - but closed-loop systems do not, making them the more popular choice for urban companies.


The maximum length of the pipe will be 400m depending on the heat pump size you require. This means that, in total, the average system will need between 600 and 1200 square metres of land that is clear of trees and buildings.


Final Thoughts - Will Heat Pumps Replace Gas Boilers?


A white gas boiler on a turquoise background with the text 'Heat Pumps vs Gas Boilers' written next to it.

Although heat pumps are very sustainable and much more efficient than the standard gas boiler, they have some glaring limitations in the real world that don't always make them a suitable, direct replacement for gas boilers.


Firstly, they can be very costly to install compared to gas boilers.


Additionally, they are not yet suitable for every property. Suppose your business is poorly insulated and you have a limited budget. In that case, improving your insulation will be a far more cost-effective way of limiting your energy use (and therefore lowering your monthly bills).


Something else worth considering is that to replace your boiler with a heat pump, the radiators will likely need to be replaced.


And from our experience, we have found that many gas boiler installations are not set up optimally. Each unit can be programmed to better reflect the use of the building and could ultimately save you money on your bills. If in doubt, we can always check the basic installation is correct for you.


For these reasons and more, heat pumps may not yet be a viable alternative to gas boilers for everyone. However, as the energy cost gap closes, the numbers may eventually become more favourable toward heat pumps.


Hybrid systems - making use of both a heat pump and commercial boiler – are also becoming available. The advantage here is that the heat pump takes some of the strain - allowing the boiler to run for longer and reducing energy costs.


If you're unsure which to opt for or are wondering if switching to one rather than the other will benefit you, hybrid systems may be the way to go.


More About Javelin Controls


Javelin Controls Limited was originally formed 14 years ago and has subsequently developed to the stage where, in addition to supporting Hampshire and West Sussex County Councils, both directly and indirectly, in all things controls-related, it has also successfully completed a £1.3M contract for Hampshire County Council providing their schools portfolio with Boiler Energy Efficiency controls packages.


Get in touch with the Javelin Controls team to transform your work environment with a high-quality building management system. We’ll be more than happy to discuss your control and HVAC system requirements and find a customised solution to suit your business needs.


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