Outside Boilers and Is Installing an External Boiler Good or Bad?

James Elston
Written by James Elston
Updated on 27th January 2024
Posted on 5th December 2023
Topic: Boiler Advice
outside boilers

Tired of your boiler taking up valuable space indoors or disrupting your peace with its noise? Installing an outside boiler might be the solution you’re looking for.

However, there are both benefits and challenges of external boilers to consider before making this decision.

In this blog, our heating experts at Boiler Central explore the advantages and drawbacks of outside boilers, discuss some top options in the market, and provide guidance on safety, regulations, and cost comparisons.

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Guide to Putting Boilers Outside Overview

  • Why is it a good idea? Installing an outdoor boiler can provide space efficiency, reduced noise levels and improved access for maintenance.
  • Why is it a bad idea? Challenges of installing an external boiler include weather-related damage, increased installation costs and heating efficiency concerns.
  • What to think about – Consider factors such as space, noise levels, installation costs and safety regulations before making a decision on whether to install an outdoor or indoor boiler.

Benefits of Installing an Outdoor Boiler

Outdoor boilers, including oil and gas boiler models, have become increasingly popular due to their space-saving capabilities, reduced noise levels, and easier maintenance access.

But what does this mean for homeowners in terms of gas consumption of their new boiler? We will analyse these advantages further in the upcoming parts.

Space-Saving Solution

One of the primary motivations for installing an outdoor boiler in a small property is the lack of indoor space for a heating system.

By moving the boiler outdoors, you can free up valuable space indoors, potentially eliminating the need for a dedicated boiler room or storage area. This is especially beneficial for those with limited indoor space, such as small apartments or tiny homes.

Outdoor boilers come in various sizes and heating capacities. Choosing the appropriate size boiler is necessary to guarantee the best heating performance and avoid excessive energy use.

By taking the time to choose the best outdoor boiler for your property, you can maximise the space-saving benefits and improve your overall living experience.

Reduced Noise Levels

Boiler noise can be a significant disturbance, especially when located near living or sleeping areas. Indoor natural gas boilers typically produce noise levels ranging from the quietest boilers at 40 dB to 60 dB. By installing a boiler outdoors, you can significantly reduce noise disturbances inside your home.

Many outdoor boiler models are designed to operate with minimal noise, such as the Viessmann Vitodens 200, Grant Vortex Pro XS 26, and Vaillant ecoTEC Plus Range, which have noise levels as low as 41 dB and 45 dB respectively. These external boilers provide efficient heating without compromising your home’s peace and quiet.

Easier Maintenance Access

Outdoor boiler installations offer several advantages in terms of maintenance compared to boiler indoors. Their accessible positioning allows for easier servicing and repair work without entering the property.

This means less disruption to your home and a cleaner environment during maintenance procedures, making it an ideal choice for those considering a new boiler.

Outdoor boilers, such as those from Mistral, feature multi-directional flue outlet options, pre-punched pipe entry points on both sides and the back, and a lockable cabinet door for easy access to the combustion chamber.

These features, along with the durable boiler casing, make servicing and maintaining your outdoor boiler a breeze, ensuring your heating system operates at its best for years to come.

Can You Put a Combi Boiler Outside?

While outdoor combi boilers come with several benefits, there are also challenges to consider. Some of these challenges include weather-related damage, increased installation costs, and heating efficiency concerns.

We will examine these issues in more depth in the upcoming parts.

Weather-Related Damage

Outdoor boilers are more vulnerable to damage from inclement weather, including freezing pipes and component degradation.

Freezing temperatures can cause pipes to freeze and burst, leading to water damage and costly repairs. Prolonged exposure to rain, snow, and moisture can also cause rust and corrosion, affecting the boiler’s components and overall efficiency.

Steps such as adequate maintenance, insulation, and weather protection are necessary to guard your outdoor boiler against severe weather conditions. These measures can help prevent damage and ensure the longevity of your boiler.

Increased Boiler Installation Costs

Installing a combi boiler outside can be more expensive than an indoor new boiler installation due to factors such as additional building and infrastructure, more complex fuel delivery systems, and possible rerouting of gas connections.

Rerouting gas connections can cost between £400 to £900, depending on the complexity of the rerouting. Insulation for an outdoor boiler can range from £100 to £4,000, depending on the size and type of insulation.

Moreover, extending pipework in outdoor boiler installations may cost between £500 and £1,000, depending on the requirements for fresh flue, pipework, and other materials. While these additional boiler costs can be a deterrent, the benefits of an outdoor boiler may outweigh the initial expenses for some homeowners.

Heating Efficiency Concerns

Outdoor boilers may experience reduced heating efficiency due to increased exposure to harsh weather conditions and potential oversizing. Cold temperatures can result in increased energy consumption and higher heating bills.

Furthermore, an oversized boiler may have a higher minimum output, which can lead to inefficient operation throughout the year and on/off boiler cycling behaviour, further decreasing efficiency.

Choosing the correct size and adopting measures to reduce heat losses, like adequate insulation and weather protection, is vital to guarantee the best efficiency for your outdoor boiler. Regular servicing and maintenance can also help keep your boiler running at its best, ensuring optimal heating flow.

Top External Boiler Options in the Market

If you’re considering a condensing boiler or an external boiler for your home, there are several top options available in the market. Oil and biomass boilers are among the most popular choices.

The Mistral Combi Standard Efficiency boiler range is a notable model. It offers efficient full heating and instantaneous domestic hot water facility. The Worcester Bosch Greenstar Heatslave II External Boiler is another top choice, available in power outputs of 18kW, 25kW, and 32kW.

The Mistral Mega Combi Standard Outdoor range is another option. It is suitable for implementing in larger installations such as barn conversions and country houses. This range provides:

  • Extremely efficient full heating
  • Instant domestic hot water supply
  • Fully insulated boilers
  • Weather-resistant casing

These features ensure longevity and reliable performance.

Safety Considerations for Outdoor Boilers

Safety is paramount when installing an outdoor boiler. Proper clearances must be maintained for maintenance and repairs, with a minimum distance of 1 meter between the boiler and any nearby windows, doors, or vents. Additionally, flammable or combustible materials should be avoided near the boiler to prevent potential fire hazards.

It’s also necessary to make sure your outdoor boiler is equipped with safety features like:

  • Pressure relief and temperature control devices
  • Water level monitoring
  • Flame safeguard mechanisms
  • A gas detection system

By taking these safety considerations into account, you can protect your home and family while enjoying the benefits of an outdoor boiler.

Regulations and Legalities of Outdoor Boiler Installation

In the UK, regulations require adherence to building regulations and Gas Safe Register guidelines for outdoor boiler installations.

For compliance, hiring a Gas Safe registered engineer is necessary to guarantee correct installation and safety. For external oil boiler installations, consulting with an OFTEC registered professional is crucial to ensure compliance with regulations and safety requirements.

Being aware of rules related to the placement of an oil tank on a property is also significant to avoid spreading fires in the home to the oil tank. By following these regulations and guidelines, you can ensure a safe and compliant outdoor boiler installation.

Tips for Choosing the Right Location for Your Outdoor Boiler

Choosing the perfect location for your outdoor boiler is crucial to guarantee the best performance and easy maintenance. Consider the following factors when choosing a location:

  • Accessibility for maintenance and repairs
  • Proximity to areas with high hot water demand, such as bathrooms and kitchens
  • Minimising noise disturbances in living or sleeping areas

By considering these factors, you can ensure that your outdoor boiler is in an optimal location for efficient operation.

In addition, make sure there is adequate clearance around the boiler for proper ventilation, servicing, and compliance with local regulations and guidelines. By carefully considering these factors, you can select the perfect location for your outdoor boiler, ensuring it operates efficiently and safely.

Cost Comparison: Outdoor vs Indoor Boilers

When weighing up the costs of outdoor and indoor boilers, considering elements like installation, energy use, and upkeep costs is important. Outdoor boilers generally have higher installation costs due to additional insulation, rerouting gas connections, and extended pipework.

However, the ongoing costs for outdoor boilers may be similar to those of indoor boilers, depending on factors such as insulation, energy consumption, and maintenance expenses.

Oil boilers are typically more expensive than gas boilers, costing approximately £1,400 to heat a 3 bedroom house for a year, compared to £700-£1,000 for gas boilers.

Weighing the costs and benefits of outdoor versus indoor boilers can help you make an informed decision about which option is best for your home. It’s also essential to obtain quotes from multiple boiler installers and compare them to secure the most competitive price for your installation.

Making the Decision: Is an Outdoor Boiler Right for Your Home?

The decision on whether an outdoor boiler suits your home depends on elements like available indoor space, noise issues, and financial considerations. If your home has limited indoor space or you’re looking to minimise noise disturbances, an outdoor boiler might be an ideal solution.

On the other hand, if the additional installation costs and potential efficiency challenges are a significant concern, you may want to consider alternative options such as heat pumps or solar thermal panels.

Regardless of your selection, making sure of correct installation, maintenance, and adherence to safety regulations is vital to maximise your heating system’s efficiency.


In conclusion, outdoor boilers offer several benefits, such as space-saving, reduced noise levels, and easier maintenance access.

However, they also come with challenges, including weather-related damage, increased installation costs, and heating efficiency concerns.

By carefully considering these factors and consulting with professionals, you can make an informed decision about whether an outdoor boiler is the right choice for your home.

Frequently Asked Questions

Are outside boilers any good?

Location and leak safety make outside boilers a great choice, especially for those with oil boilers. Low risk of property damage make these an ideal option.

Can you have a boiler outside the house?

Yes, it is possible to have a boiler installed outside the house. As long as you follow all the relevant building regulations and consult a Gas Safe Engineer for guidance, you can install external boilers like the one by Worcester that are specifically designed for this purpose.

What is an external combi boiler?

External combi boilers are an efficient and cost-effective way to provide heating and hot water with no need for a cold storage tank or hot water storage unit. They have a durable weatherproof casing, allowing them to be installed outside, and can be controlled via an indoor programmer.

Are back boilers now illegal?

Back boilers have been illegal to install new since 2005 due to potential hazardous consequences such as flue gases entering the pipework and a fire risk from high temperatures.

What safety features should an outdoor boiler include?

Outdoor boilers should be equipped with pressure relief devices, temperature control devices, water level monitoring, flame safeguard devices, and gas detection systems to ensure safe operation.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 5th December 2023
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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