What to consider when choosing the right boiler

Choosing the right boiler for your home can feel overwhelming because there’s so much choice out there; not only do you need to think about boiler type, but you also need to think about fuel type and boiler size. It’s important that you carry out proper research into choosing the right boiler so you don’t waste your money on a boiler that isn’t fit for your home or your household. In this complete guide, we’ll walk you through everything you should consider before investing in a new boiler and explain what options you have.

What Fuels Boilers in the UK?

In the UK, most boilers are fuelled by one of three elements:

1. Oil

2. Gas

3. LPG (liquified petroleum gas)

Only households connected to the national grid can be fuelled by a gas boiler. Off-grid homes have the choice of heating oil or LPG.

What to Consider When Choosing the Right Boiler

1. Hot Water Usage

Before choosing your boiler, think carefully about how much hot water your household uses in a day. This will help to determine what size boiler is right for you. Consider the following:

  • How many showers are taken in your household per day?
  • How many sinks do you have in your house?
  • How many baths do you have in your house?

2. Size of House

The size of your home is one of the most important considerations when choosing the right boiler. The most common method to measure your boiler output is in kW. As a general rule, 1kW is required per 10m3.

You should also consider the following:

  • How many bathrooms are in your house?
  • How many people are typically in your house at a given time?
  • How many rooms are heated?
  • How big are the radiators in these rooms?

If you have a large house and/or a large household, then a combi boiler is not recommended. You should instead consider a heated-only boiler or a system boiler, and you’ll need to think about the size of the boiler, too.

3. Home Insulation

A well-insulated house offers a range of benefits, however the key advantage is that you’ll be able to cut down on heating consumption and lower energy bills without compromising on comfort. The type and size of boiler you choose will be determined by the level of insulation your property has.

The type of property that you have can influence how insulated your house is. With fewer external walls, semi-detached houses and terrace houses tend to hold heat better than detached houses.

There are a number of other characteristics that will impact how well-insulated your home is, so you should answer the following questions:

  • Do you have cavity wall insulation?
  • Do you have loft insulation?
  • Do you have double glazing?
  • How many windows do you have?

4. Boiler Efficiency

Sourcing the most efficient oil burner, gas boiler or LPG boiler is typically high on the priority list. You can find extremely efficient boilers nowadays, which is better for your purse and the environment.

Condensing boilers are proven to be more efficient than normal boilers and will help you to save energy. As the name suggests, they use the hot water return to condense the gases in the flu exhaust to gain recovery heat to the water. Condensing boilers typically have an efficiency level of around 90% or more.

A condensing boiler will also reduce the carbon dioxide you emit into the atmosphere. An estimation of around 60% of the carbon dioxide generated by domestic use comes from home boilers. If every British home installed a high efficiency boiler, we would reduce the amount of carbon dioxide reaching the atmosphere by 13 million tonnes! In fact, with a drive to cut carbon emissions and further improve energy efficiency, a condensing boiler must be fitted by law to all new properties.

The only disadvantage of a condensing boiler is the fact they are more complicated than a standard boiler. As a result, there’s a greater chance of something going wrong. However, they are only getting more and more reliable as time goes on.

There are government grants available to help you make your home more energy efficient, this includes upgrading your boiler. For more information on this, the Energy Saving Trust is a helpful resource to explore.

5. Location

If your property isn’t connected to the natural gas grid in the UK, then choosing a gas boiler is not an option to you. The two most popular alternatives are an oil fired burner or an LPG boiler.

If there is a community oil buying scheme in your local area, then it may be worth investing in an efficient oil burner. Oil clubs allow local residents to club together and bulk buy oil to cut down on deliveries and take advantage of bulk savings.  

If you live somewhere particularly remote, for example the roads leading to your house may be inaccessible to oil trucks at certain times of the year, then you may want to consider a larger heating oil tank for extra capacity. Average domestic tank capacities will range from 1,000 litres (220 gallons) to 1,360 litres (300 gallons).

How to measure the efficiency of a boiler

From 1999 to 2015, boilers in the UK were given a SEDBUK (Seasonal Efficiency of a Domestic Boiler in the UK) rating to measure efficiency. However, since September 2015, every new oil burner, gas boiler or other type of boiler is given an ErP energy label.

SEDBUK ratings were measured on a scale of A to G. Boilers in the top rating were classed as A boilers with an efficiency level of 90% to 91.3%. ErP ratings are also alphabetical, however the principles used to measure efficiency are slightly different, which can lead to different ratings.

Practically all modern gas condensing boilers in the UK are given an A rating on the ErP scale, so if you’re looking for further detail it’s recommended to review the SEDBUK rating, too.  

Pros and Cons of Oil Fired Burners, Gas Boilers and LPG Boilers

1. Oil Fired Burners


Suitable for off-grid homes: If your home isn’t connected to the gas grid, then an oil fired burner is a practical and efficient option for you. Oil boilers are the most popular choice for households off-grid.

Bulk savings: With an oil boiler burner, you can purchase fuel in bulk and take advantage of bulk savings. Doing this when heating oil prices are low (typically in the summer months) can save you a significant amount of money in the long-run. This is something you can’t do with piped gas. What’s more, you can also save on delivery costs.

Choice of supplier: Homeowners have more choice when it comes to oil supplier. With a gas boiler, you’re typically tied to a contract which is not the case with an oil boiler burner. This gives you more flexibility to shop around and compare heating oil prices and heating oil suppliers.

Efficient: Oil is a highly efficient fuel, which helps to keep down costs. The most efficient oil burners are modern, condensing boilers which are typically 90% (or more) efficient. To achieve this, condensing boilers make use of hot flue gases that a standard boiler wastes. If you’re investing in a new oil burner, it’s worth considering a condensing boiler as they’re readily available and should lower your heating bill in the long-term.

Safe: Oil is not prone to explosion as gas is, and doesn’t produce carbon monoxide. You can also store your oil tank outside of your property for extra safety.

Easy to upgrade: If you want a new oil burner, it’s usually easy and quick to replace.


Price fluctuations: There are many factors that affect the price of heating oil, which means prices can fluctuate. Of course this can play in your favour, however you still have to accept that prices can fluctuate unexpectedly.

Forward planning: With an oil fired boiler, you’re responsible for buying your own heating oil. If you don’t forward plan, you risk facing steep delivery charges for quick turnarounds. And, without forward planning, you may end up in a situation where you run out of heating oil.

Space: To store your heating oil, you need a heating oil tank which can take up extra room. Plastic (moulded polyethylene) tanks are not the most attractive, yet they remain a popular choice because they’re durable and relatively inexpensive. You also don’t have to worry about maintaining a plastic tank’s interior over the years as you would with a metal tank.

Heating Oil Theft: If you store your heating oil outside, you are vulnerable to heating oil theft. However, there are a whole host of effective methods you can use to deter thieves and protect your oil.  

2. Gas Boilers


Affordable: Gas is used to fuel most UK homes, and natural gas is a relatively cheap source of fuel, especially compared to electricity.

Stable prices: The cost of natural gas tends to remain relatively stable throughout the year, which can help you plan financially.

Convenient: Unlike with oil boiler burners, you don’t need to monitor your heating oil levels or schedule deliveries. As long as you’re connected to the gas grid, you shouldn’t need to worry about not having a supply.


Unavailable to off-grid houses: There are approximately 4 million homes in the UK who are not connected to the gas grid. A gas boiler that runs on natural gas is not a viable option for these houses.

More susceptible to faults: Gas boilers are typically made up of more internal moving parts. As a result, there’s a greater chance that one of these components will develop a fault, affecting the functionality of your boiler. This could also incur added costs for maintenance and repair.

Potential gas leaks: Although unlikely, with a gas fuelled boiler you are at risk of a gas leak. Gas boilers produce carbon monoxide, and therefore a leak can be hazardous. This is why it’s vital to install a functioning carbon monoxide monitor if you have a gas boiler.

Expensive to install: The initial cost involved with installing a new gas boiler is often costly.

3. LPG Boilers


Lower upfront cost: Typically, installing an LPG boiler has lower up-front costs than an oil burner boiler or a natural gas boiler.

Environmentally friendly: Like natural gas and oil, LPG is a fossil fuel. However, it is a cleaner source of energy than oil, producing about 15% less carbon.

Suitable for off-grid homes: If your home is not connected to the gas grid then, like an oil fired boiler, a LPG boiler is an alternative solution.


Storage tank: Like with an oil boiler, you will need a storage tank for your LPG boiler in order to store the LPG.

Higher ongoing cost: The unit price per kWh of energy is higher than oil and natural gas, so an LPG boiler is likely to cost you more over time.

Organising delivery: Like with an oil boiler, you need to monitor your levels of LPG and be proactive in ordering more so you don’t run out.

What are the Different Types of Boiler?

1. Combi Boiler

A combi boiler (combination boiler) is the most common type of boiler in UK homes. In fact, combination boilers now account for over half the domestic boilers installed in Britain every year. A combi boiler can heat your home and give you hot water on demand. They can run on gas, oil or LPG.


Compact: Combi boilers tend to be compact because they provide two household functions in one, which is one of the most attractive features. Because they’re compact and popular, they also tend to look more modern and sleeker.

Efficient: Modern combi boilers are typically much more efficient than older boilers. New combi boilers in the UK should have an efficiency rating of 90% or more.

Affordable: Because combi boilers are so popular, it’s easy to find replacement parts if necessary. Also, installations are typically more straightforward and therefore less costly.

Instant hot water: Combi boilers give you instant hot water so you don’t have to wait around before taking a shower or warm bath.


Small households only: You should only consider a combi boiler if you have a small home and/or a small household. This is because, with a combi boiler, hot water can only be delivered to one place at a time. For example, you won’t have access to hot water for cleaning the dishes if someone else is running a hot shower.

Relies on strong mains pressure: If you install a combi boiler and your mains supply has poor pressure, then your shower head and taps won’t have strong pressure either.

No immersion heater: Combi boilers don’t have an immersion heater so, if your combi boiler broke down, there’s no backup solution. You would be without hot water and without heating until you could have the boiler repaired or replaced.

2. Heat-Only Boiler

A heat-only boiler, also known as a regular or conventional boiler, is a two-tank system. With this type of conventional heating system, you’ll typically have a tank of cold water situated in the loft and a hot water cylinder situated in the airing cupboard. The cold water is fed into the boiler where a heat exchanger will warm it up. This is then pumped into your hot water cylinder and stored until you turn on your shower or taps. Regular boilers can run on gas, oil or LPG.


Good for large homes/households: As heat-only boilers store hot water in a tank, multiple people in your household can access hot water at the same time.

Immersion heaters: You can fit an immersion heater to the back of your hot water tank to continue getting hot water even if your boiler breaks down.


Requires a lot of space: With two separate tanks required, you need a bit more space to install a heat-only boiler. You also need to store the cold water tank at a height, which demands a larger home.

No instant hot water: Once you’ve used up all the hot water stored in the hot water tank, you’ll have to wait again for more water to be heated.

Susceptible to heat loss: As the day goes on, the hot water sitting in the tank will lose some of its heat. This means you need to think about effective insulation to minimise heat loss.

3. System Boiler

Also known as closed vent boilers, system boilers have a hot water cylinder and an expansion vessel built into the boiler. They can be fuelled by gas, oil or LPG.


Good for large homes/households: Like a heat-only boiler, a system boiler can distribute hot water to multiple taps at a time. This is ideal for larger households where more than one person needs hot water at a given time.

No cold water tank: Unlike a heat-only boiler, a system boiler doesn’t need a cold water tank in the loft. This means it should take up less space than a heat-only boiler would. However, as it still requires a hot water cylinder, it takes up more space than a combi boiler.

Water pressure: With a system boiler, you’ll enjoy a stronger water pressure from your taps compared to a combi boiler. This is because the water supply is taken directly from the mains.


No instant hot water: Once you’ve used up all the hot water stored in the hot water tank, you’ll have to wait again for more water to be heated.

Susceptible to heat loss: As the day goes on, the hot water sitting in the tank will lose some of its heat. This means you need to think about effective insulation to minimise heat loss.

We hope this guide has been helping for choosing the right boiler, whether you want a new oil burner, a gas boiler or an LPG boiler. If you have any questions, please don’t hesitate to contact the Rix team.