We’ll walk you through the process of buying a reliable boiler, from deciding between a combination, regular, or system boiler to determining the optimal size for your home’s heating needs.

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Which kind of boiler would you recommend I get?
Boilers that run on gas, oil, and LPG

The majority of homes in the UK are wired into the country’s natural gas distribution system, and as a result, they are outfitted with a gas heating system that includes a gas boiler. However, there are options available for the 15% of homes that do not have access to a gas network (Energy Savings Trust, May 2021). These options include installing an oil boiler, a boiler that runs on liquid petroleum gas (LPG), or a wood-burning stove that has a back boiler (which come with another set of environmental implications). Do you know what kind of fuel you’ll need? Take a look at our reviews of gas boilers, oil boilers, and LPG boilers.

System, heat-only, and combination boilers are all available.

Combination boilers (also known as combi boilers), heat-only boilers (also known as conventional or regular boilers), and system boilers are the three primary varieties of gas boilers that are typically available.

On-demand hot water is made available by combi boilers. Ideal for homes or apartments with limited space and modest water requirements (eg one bathroom).

Heat-only boilers, also known as regular boilers, call for the installation of a cold water feed tank and a hot water storage tank, which are typically located in the loft. Ideally suited for use in larger homes that have a greater requirement for water (eg multiple bathrooms being used at the same time).

System boilers are very similar to regular boilers; however, system boilers do not need a cold water feed tank and have additional components built directly into the body of the boiler. Ideally suited for use in larger homes that have low water pressure and a high water consumption rate (eg multiple bathrooms being used at the same time) Your heating engineer will be able to walk you through the various types of boilers and recommend the one that is most suitable for your requirements after walking you through each type. Find out more about the benefits and drawbacks of boilers by reading our advice guide on the various types of boilers.

Why is it so important that the boiler be efficient?


According to the Department of Business, Energy, and Industrial Strategy’s 2021 Heat and Buildings Strategy, residential buildings in the United Kingdom are responsible for 77.1 mega tonnes of greenhouse gas emissions, which equates to approximately 2,666 kilogrammes of carbon dioxide equivalent per home on average. The cost of heating our homes is responsible for approximately 17% of the total carbon emissions in the UK. The United Kingdom is on track to achieve carbon neutrality by the year 2050. In order to accomplish this, the annual emissions from homes will need to be cut by 95%, coming in at just 138 kilogrammes by the year 2050. (Energy Savings Trust, 2021). The transition to a boiler that runs on a fuel other than fossil fuel is neither simple nor inexpensive at the moment. For the foreseeable future, the vast majority of us will be getting boilers that run on gas or oil. Because of this, selecting the right boiler should be one of your top priorities because it can help reduce your carbon footprint and save money on your energy bills. However, since 2005, all gas boilers have been required to be condensing boilers. If you are replacing an old, non-condensing boiler with a modern, condensing system, you will see the greatest savings possible. In addition, as of 2018, the legislation known as “Boiler Plus” passed by the government mandated that all newly installed boilers must have a minimum ErP efficiency of 92%, in addition to having time and temperature controls fitted. You are able to sort our reviews of boilers according to their efficiency ratings; however, in practise, there is not much of a difference between modern condensing boilers because they are all efficient.

heating systems with low carbon emissions

boilers in home

We will all eventually be required to install low-carbon heating systems in order for the United Kingdom to meet its net zero target by the year 2050. People who heat their homes with renewable sources of energy are eligible for financial incentives through programmes like the Renewable Heat Incentive, which makes many of these systems immediately available for installation. Our in-depth guides on can provide you with additional information regarding low-carbon heating, such as how it operates, how much it costs, and whether or not it is appropriate for your home.

Heating of water from the sun Panels that absorb the sun’s energy and convert it into thermal energy can be used to heat water for domestic use.

Pumps that draw heat from the ground A system consisting of water pipes that are buried underground and connected to a network, which draws natural heat from the ground and transfers it to your home’s heating system.

Air-to-air and air-to-air heat pumps Functions in a manner that is analogous to that of a ground source heat pump, but rather than drawing heat from the ground, it draws heat from the surrounding air, which is then compressed and heated to a higher level.

Heating system controlled by electricity Reduces the amount of carbon dioxide that is emitted from your home (although this benefit is null and void if the electricity you use comes from renewable sources) You are still able to reduce both your carbon footprint and your heating costs by using a gas or oil boiler. Find out the best advice we have to offer to lower your heating costs.

How to Determine the Appropriate Boiler Size for Your Home

boiler size

The physical size of the boiler (that is, whether it will fit in the space you have designated for it) and the capacity to heat and provide hot water are the two aspects to consider when selecting the appropriate boiler size. The latter is expressed as a number in kilowatts (kW), but it is commonly referred to as simply the “boiler size.” Because the ideal boiler size is determined by a number of factors, including the number of bathrooms in your home, it is impossible to give you an exact recommendation.

How many people do you have living with you at this time? Do you frequently host large get-togethers at your house? What is the total number of radiators in your home? Nevertheless, as a general rule, the higher the kW boiler you need, the greater the amount of heat and hot water your home requires. Your heating engineer will be able to guide you through the process of selecting the appropriate size of boiler for your home, and their expertise will be essential to ensuring that you meet all of your hot water and heating requirements.

We describe the amount of hot water and space that can be heated by each boiler, as well as offer some insight into the kinds of homes that are a good fit for each model. We also provide you with the dimensions of the boiler so that you can determine whether or not it will fit in the area that you have designated for it.

Investing in a dependable boiler

When deciding which boiler to purchase, dependability will be by far the most important consideration for you to take into account. As a result, each year we put in a lot of effort to determine which brands are reliable and which ones aren’t and rank them accordingly. In 2021, we conducted a survey consisting of 8,001 individuals who had purchased a boiler within the previous six years and asked them what year their boiler had its first problem (if at all). We are able to deduce from this how many boilers will continue to function without issue for the first six years.

graph showing percentage of fault free boilers versus age

The most suitable heating system for a modest home

If you have a small apartment with only one bathroom, a combination boiler is the most suitable option for your home’s heating needs. Because a combi boiler does not require room for a hot water cylinder to store the hot water or a large cold water feed tank, the boiler does not take up valuable space in a home that may be at a premium for living area. We are of the opinion that a compact combination boiler with an output of less than 24 kW is the best option. Choose from one of our Best Buy small combi boilers to ensure that you get the best possible product for your money. Find out if you are qualified to receive a grant or free boiler by reading this guide.

The most efficient heating system for homes with two or three bedrooms

For a house with a family of about three or four people, you’ll have to decide between a small heat-only boiler or a combi boiler of about the same size. If you have a large family, multiple bathrooms, and enough space to store a hot water cylinder and a cold water storage tank, then the advantages of a heat-only boiler may start to outweigh those of a combi boiler. After completing an inspection, a heating engineer with the appropriate training will be able to offer advice and assistance with your decision. However, make sure you purchase either a small heat-only boiler or a mid-size combination boiler from Best Buy.

The most efficient heating system for a home with four bedrooms

It is likely that a heat-only boiler will be the most suitable option for a larger home. Although you will need space in the loft for a hot water storage cylinder and a cold water feed tank, a heat-only boiler is almost always the best choice for a larger home with multiple bathrooms. This is because a heat-only boiler only generates heat. You will need either a small or a medium-sized heat-only boiler, and the size you need will be determined by the size of the home and how well it is insulated.

The top-rated heating appliance for residences with low water pressure

If you live in an area that has low water pressure, or if you live in a large home where you’ve converted the loft and don’t have space for a cold water feed tank, then a system boiler could be your saviour. This is also the case if you live in a home that is too small for a conventional boiler. System boilers do not need a cold water feed tank, and because they use a pressurised system, the problem of having a low mains water pressure is significantly reduced when using one of these boilers. By reading through our reviews of system boilers, you can ensure that you buy one of the very best brands on the market. By getting the best boiler service, you can ensure that your boiler is in the best possible condition.

Where to find the most qualified boiler installers

It is recommended that you have a professional install a new boiler. You can locate a qualified heating engineer by searching the Gas Safe Register, or you can use Which? Trusted Traders to locate a heating engineer in your area that you can rely on. However, despite the fact that you will not be the one to actually install the boiler, there are still important choices that need to be made. Find out what you need to ask and tell your engineer when they visit to give you a quote, what you should expect from a proper boiler installation quote, and what checks you can carry out after the new boiler has been installed by reading the following information.

Obtaining a price estimate for installing a boiler


It shouldn’t be a quick conversation when you get a heating engineer to assess your home and give you a quote for a new boiler. Instead, the conversation should take some time. A qualified installer should take the time to perform a comprehensive survey of your home, learn about your heating and hot water requirements, and only then give you a recommendation on the type and brand of boiler that is best suited for your home. Before you start a conversation with your installer, here are six questions you should ask yourself in order to get the most accurate advice and price estimate possible:

What do you do with the hot water that you have?

Do you routinely require the supply of hot water to more than one tap or shower at the same time?

Do you currently have or do you have plans to install a pumped power shower? In most cases, combi boilers cannot be used in conjunction with showers that are equipped with powerful electric pumps. If you choose a system boiler, heat-only boiler, or combi boiler, however, you will not be able to keep the power shower you currently have.

Does the amount of hot water you use fluctuate throughout the year?

Do you routinely have friends stay at your house, or do you frequently throw big parties or get-togethers for the holidays? If you anticipate significant increases in the demand for hot water, you should look into purchasing a boiler that is capable of meeting this challenge.

Do you have any plans to make improvements to your house? Notify your installer if you intend to add an extension, convert your loft into a living space, construct a new bathroom, or install underfloor heating. They might give you a different recommendation depending on the home improvements you have planned.

Are you experiencing any issues with the heating system that you currently have? Do radiators take an excessively long time to warm up? Does your water move very slowly through your pipes? Talk to your installer about any concerns you have or problems you’ve noticed with the performance of your current system.

Which brand of boiler do you want, exactly? According to the results of our survey conducted in 2021 on boilers, the worst brand had nearly twice the likelihood of developing a fault within its first six years compared to the best brand. Because some engineers receive financial incentives to install boilers manufactured by certain brands, you need to make sure that the brand of boiler they recommend is one that will benefit you, not just them. Our opinion is that a good installer will discuss some, if not all, of the points listed below. If you don’t hear them, you should inquire about them yourself.

How do you plan to get rid of the condensate?

The water from the boiler is transported via these pipes to the drainage system. Pipework that is exposed to the elements should be kept to a minimum, but if it is unavoidable, the installer must take precautions to protect it from freezing temperatures in accordance with the guidelines provided by the manufacturer.

What kind of treatment does the water in the boiler get?

Over time, sludge accumulates in heating systems, which results in cold spots on radiators and a protracted time to reach the desired temperature. The majority of systems require a gravity flush, but those with a significant amount of sludge buildup require a power flush. Systems need to be cleaned and flushed regularly. According to estimates provided by 24 Which? Trusted Traders in February 2022, the price of a power flush for a five-radiator system can range anywhere from £300 to £750, with a typical cost of £481 (based on the prices listed). After cleaning your heating system, have the installer ensure that a chemical inhibitor is added during the refilling process. This will reduce the rate at which sludge, corrosion, and scale buildup occur.

Do I need to install scale reducers or system filters?

If you install a new boiler into an outdated heating system, you are setting yourself up for future reliability issues.

Filters, which can typically be purchased for a price ranging from £70 to £200 (Screwfix, 2021), prevent sludge and debris from entering your boiler, thereby extending the life of the boiler. Scale reducers are helpful in areas with hard water and can again contribute to the longevity of your combination boiler. Inquire with your installer if they are required.

What kind of height will the plume reach?

This is the water vapour that is escaping through the flue of your boiler. Ask the person who is installing the system how large of a plume you can expect to get and where it will be located. Will it be an annoyance to the neighbours? In the event that it is necessary, the plume can be extracted using an additional pipe.

Should I get new radiators for my home?

Radiators that are several decades old may have internal corrosion, making them inefficient, and necessitating their replacement. Inquire with your installer about their recommendations.

Are there any other steps that can be taken to save energy?

Since 2018, the legislation known as “Boiler Plus” has mandated that all newly installed gas combi boilers must include at least one of the following four energy-saving measures: flue gas heat recovery, load-compensating thermostats, weather-compensating thermostats, or smart heating controls. Either consult with the person who installed your boiler to get advice on which one is best for you, or educate yourself further on boiler controls and thermostats. Because the cost of installing a new boiler can typically range anywhere from approximately £1,400 to £7,000, getting at least three different quotes is highly recommended to ensure that you are getting the best possible deal. Do not let yourself be fooled by any discounts that are advertised on the front page; instead, consider the overall cost of the boiler as well as the labour charges. It’s possible that the installation company you choose won’t give you the option to pick the boiler model you want, instead recommending a replacement boiler they think is best for you. This is due to the fact that many heating engineers receive financial incentives to install specific brands.

What components of a boiler installation should be included in the estimate?

boiler installation

The items that are going to be paid for with your money should be itemised in a way that is easy to understand and correctly presented in any quotes that you receive. On the other hand, we have come across a great deal of installation quotes that are puzzling and hard to comprehend. The following are some of the things you should search for in a quote for installation that is correctly itemised:

The make, the model, and the cost of the boiler that is going to be installed It is necessary to provide an explanation as to the basis for recommending this boiler, including a discussion of its size as well as its type (combi, heat-only, or system).

Additional controls for the heat These ought to be priced and included in the listing independently of the boiler. Where exactly the boiler is situated. It ought to be made clear whether the replacement boiler will take its place in the same location as its predecessor, or whether it will be relocated to a different location. The latter should provide an explanation as to why it is moving.

Purification of water Cleaning is necessary, but the nature of the cleaning required will vary according to the level of filth that has accumulated in the heating system. The method of cleaning that is best suited to your needs should be recommended to you by the person who installed the system. An examination of the costs of labour This is something that can change depending on how much work there is to be done.

You can figure on it being more expensive if the new boiler needs to be installed in a new location.

Costs associated with System Balancing and Post-Installation After the installation, the engineer should make sure to mention that they will perform any necessary checks, such as ensuring that your radiators are functioning properly and are properly balanced.

Clarification of the terms of the warranty

This should detail everything that needs to be done in order to keep the warranty that comes with your boiler intact, such as getting annual service.

checks following the installation of your boiler

instal boiler

Following the completion of the installation, your technician should carry out a series of safety and performance checks on your new boiler to ensure that it is operating effectively.

The results should be recorded in the back of the instruction manual for the boiler. This is an important step in the benchmark process, which is required in order to maintain the warranty on your new boiler. Additionally, you ought to make certain that your engineer registers your boiler with the manufacturer in order to activate the warranty.

If, after performing these checks, you notice cold spots on your radiators or they take an unusually long time to heat up, this could be a sign that your system has not been balanced or cleaned in the appropriate manner. You should get in touch with the installer as soon as possible.