Are External Oil Boilers a Good Choice?

Oil boilers are one of the most popular heating solutions for over 4 million UK homes that are not connected to the gas network. For many, one of the biggest attractions is the fact that it’s possible to install an oil fired boiler outside the home. But is an outside boiler really the best choice for you?


What is an Oil Boiler?

An oil fired boiler is the same as a gas fired boiler, aside from the fact it burns oil rather than gas to heat the water. Whereas gas boilers are supplied by the gas network and are self-sufficient when it comes to refuelling, an oil boiler needs a little more TLC.

You need to order a tank of oil from a supplier who will deliver in bulk. You will also need to rent or buy a storage tank to keep in the garden and refill as needed. This tank is connected to the boiler (which can be inside or outside the home depending on the model), automatically feeding it fuel as needed. The boiler will then heat and supply the water needed for your radiators and taps.

Why Choose an External Oil Boiler?

While having an external oil boiler will help to save valuable space around the home, there are many other reasons you might want to consider installing one:

  • More space indoors. Removing the boiler from your kitchen or utility room can free up space and, in the case of old, bulky boilers, remove an eyesore.
  • Less noise. Some boilers are noticeably noisy when running with humming, vibrating, banging or pinging sounds a constant irritation.
  • No carbon monoxide risk. Although not a common occurrence, carbon monoxide leaks are a real risk which can be removed by putting the boiler outside.
  • Prevent damage to home. Occasionally, boilers can leak oil which not only causes damage but can smell.
  • Easier access for servicing. Moving the boiler outside means your home is not turned into a temporary workshop during annual servicing and can improve access making your regular maintenance and the engineer’s job a lot easier.
  • Heating for outdoor buildings. If you choose the house the boiler in a garage or outhouse, it will lose a certain amount of heat to the air around it which could be a positive if the area is used as a work area or for storage.


Possible Considerations With External Oil Boilers

If you have limited outside space you may not be able to accommodate the large storage tank needed. It needs to be located in a relatively easy to access place to make delivery easier, otherwise you may need extensive piping.  All boilers radiate heat to the air around it to some degree, which is okay if this heat escapes into your home, but if the boiler is outside (and not contained in a building like a garage) this heat is completely lost, reducing energy efficiency. Heat is also lost from the pipes as it transports hot water from the boiler to the property which also makes the system less efficient. Insulation or placing the pipes underground can reduce this to some degree.

If pipes are hidden from view underneath the ground you will not notice leaks as they appear. The pipes will also lose heat into the ground. The boiler is exposed to the elements and rough weather which can increase likelihood of rusting, freezing or other damage. It also means braving all the elements when you need to carry out maintenance.

What Kind of Oil is Used in Oil Boilers?

There are two types of oil most commonly used in domestic heating: 28sec (also known as kerosene) or 35sec. They are differentiated by their thickness, i.e. how long it takes a ball bearing to pass through a set amount of oil: 28 seconds or 35 seconds. Of the two oils, 28sec is the more popular as it burns more cleanly, producing less smoke and other deposits. Another way of differentiating the two oils is their colour: 28sec is yellow and 35sec is red.

How does oil compare to other fuels?

While oil is a more expensive fuel than gas (per kWh), it is more cost effective than other alternatives on the market, e.g. LPG and electricity. A drawback of the price of oil is that it can increase in line with global supply and demand so can be difficult to predict.

Generally, it costs between £1,400 to heat a 3 bedroom house with an oil boiler for a year. Compared to between £700 – £1,000 for a gas boiler and around £1,300 for LPG, oil systems are definitely more costly. It is possible to combine an oil system with solar thermal heating or solid fuel to lower heating costs.

Oil boilers are in shorter supply than gas models and so tend to be a bit pricier by, on average, around £300 – £400.

Regulations introduced in 2007 stipulated that condensing oil boilers must have an energy efficiency of 86% or more. Modern day models exceed this delivering between 92 – 97% efficiency which is equal to the highest efficiency gas boilers.

Availability / Convenience
While oil is not an ‘install and leave’ system like gas or electricity, it requires far less refuelling than a solid fuel system like burning coal or biomass. As long as you have oil in the tank, the refuelling is automatic. However, you will need to keep an eye on the level of fuel in your tank and reorder in good time as running dry can cause damage to the system.

The need for a large storage tank on your property can be less than ideal if you’re concerned about appearances, but this can be remedied by installing it underground.

Carbon emissions
Burning oil produces twice as much carbon as gas does, but only ⅔ that of coal. Installing an A rated boiler will reduce the carbon emitted as much as possible.


What Types of Oil Boilers Are There?

Oil boilers are available as Combi, System or Conventional boilers and in a range of outputs (sizes), so there is a model to suit most homes and levels of hot water demand. In addition, all of these oil boiler types can be found as internal and external models. Oil boilers are also available with all the same modern controls as gas boilers such as TRVs, programmable timers, smart controls and thermostats. Use our comparison tool to compare oil boilers.

Installing an Oil Central Heating System

Whether you are installing an oil fired system from scratch, switching an internal for an external boiler or simply upgrading, make sure you use and OFTEC (The Oil Firing Technical Association) registered engineer.  OFTEC promotes minimum standards for oil central heating systems.

There are several regulations about the positioning on oil tank on your property and safety requirements to prevent fires in the home spreading to the oil tank. For this reason it’s really important to do your research and consult with an OFTEC registered professional when planning the installation.

Oil boilers can cost between £1,000 – £2,500 depending on the size and type. Costs of installation will depend on whether you are carrying out direct replacement or moving the boiler to a new location.

They will also vary from supplier to supplier so it’s important to get at least 2 quotes to compare. Boiler Guide can put you in touch with up to 3 registered professionals who can provide you with a tailored quote for your new oil boiler.

So, What’s the Verdict?

A lot of the concerns around external oil boilers stem from weather related issues e.g. rusting components or freezing in winter. In reality, modern external boilers have been built specifically with this in mind and many problems can be prevented through proper insulation and professional installation. In addition, you will gain space in your home and remove the potential for damage from oil leaks, noise, smell or carbon monoxide.

However, external oil boilers are more expensive and, depending on the layout of your home, can require significant piping and labour if you are placing the tank underground. For some, having a bulky boiler on view outside their home is not appealing.

High efficiency, external oil boilers are a perfectly viable option for many people and, if installed correctly, well insulated and maintained, it can be as effective as internal oil boilers without impacting on the interior of your home.

Need more guidance? We will put you in touch with up to 3 registered engineers near you who can advise you on the best oil boiler for your home.