The Best Central Heating Boilers in 2021

The best central heating boilers 2021

There’s no doubt about it, buying a new boiler for your property is a hefty investment. 

Upgrading your boiler can set you back thousands of pounds, so it’s essential you make the right choice for you, your property needs, and your budget.

Luckily, the cost of a new central heating boiler is often offset by the money you’ll save annually in heating bills as newer boilers are much more energy efficient.

In this guide, we’ve covered the following points to help you make an informed decision:

• why you should choose a gas boiler if you’re connected to the gas grid
• what type of boiler is best for your home
• why energy efficiency makes a difference to the size of your gas bills
• how to choose the right size boiler for your home
• the public votes – Britain’s best-thought-of boiler manufacturers
• why boiler guarantees are important
• the best boiler for a small flat
• which boilers you should consider for a 2-3 bedroom house
• boilers to think about for a 4+ bedroom home
• worried about which boiler to choose if you have low water pressure

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Gas, electric, oil, or LPG – why gas is best

Depending on the location of your property and other factors, you may have some choice in the fuel you choose to use for your central heating boiler. 

Fuelling your central heating by the mains gas supply is the most cost effective and energy effective method. 

It’s the cheapest source of fuel and, as you can see from the table, costs the least amount to run a boiler.

Electric central heating boilers are the most expensive way to heat your home. 

Although electricity doesn’t require a pipework installation which could save you money, it will cost you much more in annual energy bills.

If your property isn’t connected to the mains grid, a popular choice is liquid petroleum gas (LPG). 

It’s slightly more expensive than being connected to the gas mains but most mainstream LPG suppliers top up your tank automatically when it’s running low so you don’t need to worry about it.

Using heating oil to run your central heating is the other option for properties not on the main grid. 

It’s cheaper than LPG and also requires an on-site storage tank however it is being gradually phased out as a fuel source by the UK government. 

We must caveat the above figures by saying that, while a 30kw gas, oil, or LPG boiler is a good choice for a medium-sized home, an electric boiler for a medium-sized home would likely have an output rate of 12kw.

So, instead of using £4.80 per hour as the figure about, £1.92 is a more accurate, real-world figure. 

Most UK installers recommend gas boilers thanks to their energy efficiency and cheaper running costs. 

Depending on the current system you have, you may have to pay more to upgrade your heating system but over a few years you should start to see substantial financial savings.

Check out our list of the very best gas boilers in the UK right now if you’re interested!

What type of boiler do you need?

There are three main types of boiler for you to consider.

A combi boiler is best for homes with limited space

Combi boilers are the smallest type of boiler.

They are usually wall-hung units which can be neatly slotted away in a cupboard or under the stairs. 

They work by heating the water directly from the mains supply as it passes through the boiler once you’ve turned on the heating or a hot tap. 

This means you never have to wait for hot water to heat up as it’s almost instant but sometimes you lose water pressure if more than one person is using the hot tap at one time.

A system boiler is best for larger homes with higher water demand

System boilers consist of a heat exchanger and an internal expansion vessel and circulating pump. 

This means you don’t have to install a separate cool water tank in your attic.

These boilers are best for homes that have a high demand for hot water as they don’t lose water pressure, even when more than one person is using it at the same time.

A regular boiler is best for the largest homes with the highest water demand and plenty of space

Regular boilers, otherwise known as traditional or conventional central heating boilers, require loft space for a water storage tank and considerable space for the boiler itself.

They are effective at heating water for large properties that have a high hot water demand and more than one bathroom. 

They use the tank in the loft to feed the hot water cylinder and to maintain your radiator water levels and are often recommended in older properties that have unsuitable radiators for the higher water pressure of a system boiler.

Choosing the best-sized central heating boiler for your home

You need to choose the correct size of boiler for your property size in order to get the most energy efficiency from it.

Boiler output is measured in kilowatts (kW) and it allows you to work out how much it will cost to run it. 

To work out how much it will cost, you multiply the output by the cost of a unit of energy – for example, for a gas combi boiler with an output of 31kW, the sum would be 31 x 4p = £1.24.

Choosing the right boiler output for the size of your property and number of radiators you have means you won’t waste energy heating it or be caught out with insufficient power.

It’s also important to take your property’s age into consideration because this often affects the rate of insulation – the more effective your insulation the lower your heating requirements need to be.

Very old properties that were built pre-1900 are likely to have poor levels of insulation, whereas a 1950s property may have moderate insulation. 

Homes built between 1990-2000 are reasonably insulated and modern homes constructed after the turn of the millennium are usually very well insulated. 

Depending on your hot water needs and your current radiator system, you will need to choose a boiler with the appropriate flow rate.

The flow rate of a boiler is the amount of hot water it can produce in one minute. 

Your boiler installer will advise you on the minimum flow rates required for your property and confirm the mains flow rate in your area.

Britain votes – the UK’s favourite boiler brands

There are hundreds of central heating boilers available in the UK and it can be difficult to know what specification you require. 

The main areas of consideration are the flow rate, the boiler output and the energy efficiency – as well as the physical dimensions of the boiler and if you need extra space for water or fuel storage tanks.

Boiler flow rate

This refers to how many litres of hot water your boiler can produce in one minute. 

It’s measured in litres per minute but is also dependant on the water mains supply in your area. 

Even if you have a boiler with a high flow rate, the amount of water from the mains is the maximum amount you can get.  

For example, if you purchase a boiler with a flow rate of 15 but your mains only allows you 10 litres per minute, 10 litres per minute is your maximum allowance. 

Boiler output

Your boiler’s output refers to how much energy it requires to work once it’s switched on and it informs you of how much it will cost to run. 

A gas boiler that has an output of 35kW will cost £1.40 to run – the sum is the output x the unit of energy.

It’s important you choose a boiler with the right level of output for the number of rooms and bathrooms you have as well as how much hot water you generally require. 

The bigger your property and higher your hot water needs, the higher your output needs to be.

However, many UK homes have boilers with an output too high for their needs and often end up spending more money than is necessary to heat their homes. 

Your boiler installer can advise on the best output for your heating and hot water needs. 

Boiler energy efficiency rating

We should all be trying to be more energy efficient, not only for the cost of running a home but to reduce our environmental footprint.

When you switch your central heating on or use the hot water, your boiler uses energy to heat the water supply.

There is always an amount of energy that is ‘lost’ to the boiler which enables it to do its job – but the smaller the amount of lost energy there is, the more efficient the boiler is.

Much like fridges or washing machines, boilers have efficiency ratings of A to G – with A being the most effective at 90% or over.

For example, a boiler that is 95% efficient only has 5% lost energy and would be classed as grade ‘A’ and if you had a boiler like this, your energy bills would be lower.

If a boiler is only 65% efficient, you are losing a staggering 35% in energy just for the boiler to do its job correctly.

This is energy that you will be paying for but not seeing any results from so your heating bill will be considerably higher to heat the same home for the same amount of time than a grade ‘A’ boiler for example. 

Many older boilers are drastically less efficient than modern boilers, with ratings of ‘E’ or below.

UK boiler brands – rated by Trustpilot

Here we have a table of the top 10 favourite boiler brands used in the UK as rated by reviewers at Trustpilot.

Where manufacturers have the same average score, we award higher positions to the manufacturers with more reviews.

What about guarantees on my boiler?

Most boilers in the UK come with a guarantee but they vary from 1 year to 12 years so it’s in your interest to read the small print.

Having a longer guarantee means you have peace of mind should anything go awry.

However the vast majority of manufacturers do require that you get your central heating boiler serviced yearly by an engineer employed or contracted directly by them to ensure your guarantee is valid.

Here, we have a table of the minimum to maximum year guarantee from the major UK boiler manufacturers. 

It’s worth noting that different boilers from the same manufacturer are likely to have a different length of guarantee so always check before you buy.

In most cases, you need to register your boiler with the manufacturer within 30 days of installation for your guarantee to be valid. 

Some boiler manufacturers have the option to extend your warranty at a cost when you first purchase your boiler.

You will most likely also have to have your boiler serviced annually for the guarantee to remain valid.

It may also be worth checking to see if any parts or labour need to be undertaken by a registered engineer from that specific boiler company to be included in any warranty. 

The best 10 gas boilers on the market right now

Here at HomeSage, we want to help you make an informed choice when it comes to replacing your boiler. 

There are so many options available on the market today it can be a minefield knowing which boiler will suit your needs and provide good value for money.

That’s why we have developed our own unique online scoring system.

We rank boilers according to their output, energy efficiency, price, length of warranty, customer reviews on Trustpilot and price so you can compare models at a glance.

Baxi and Worcester Bosch dominate our results due to their length of warranty, efficiency ratings, and high level of excellent online reviews.

What’s more, every one of the boilers we list are condensing boilers, as they are the most efficient.

You can read more about condensing boilers here.

The best central heating boiler for a small flat

Flats tend not to need boilers with high outputs and the boilers for this type of property are designed to be small so that you can maximise your space.

For an apartment or a 1-2 bedroom flat with 1 bathroom, you’ll need a boiler with an output of up to 27kW.

There are 238 boilers available in the UK that have an output of up to 27kW and the average price is £931.

Baxi Platinum 24kw Boiler (92.69%)

All Baxi Platinum boilers come with a huge 10-year guarantee which is why they always rate so highly on our charts. 

This particular boiler measures 780mm x 450mm x 345mm.

Baxi Platinum boilers are firm favourites with UK households and installers alike due to their easy to use controls, high-quality internal brass components, and EasyFill top up system which makes balancing your water pressure easy.

The Baxi Platinum 24kw is a classic white gloss finish boiler with a smart chrome trim and hidden control panel.

Baxi EcoBlue Advance 24kw Boiler (92.51%)

Measuring 763mm x 450mm x 345mm, the Baxi EcoBlue Advance 24kw is a great choice for a small flat which needs a reliable and energy efficient boiler.

The EcoBlue range from Baxi are a recent addition to their catalogue and focus on providing excellent efficiency rates at an affordable price. 

This boiler has a traditional white durable finish and a discreetly hidden control panel.

It is compatible with the uSense smart control thermostat system so your boiler adjusts automatically to your property temperature, saving you more money. 

Worcester Bosch 2000 25kw Boiler (91.89%)

The Worcester Bosch 2000 25kw has been designed to be ultra-quiet so you won’t be disturbed by any knocks or bangs. 

It measures 724mm x 400mm x 300mm so slightly more compact than the higher rated Baxi boilers – if space is at a premium you may wish to consider this boiler. 

It comes with a 5-year guarantee as standard which can be extended to 6-years if you install it alongside the Greenstar System Filter. You do, however, get a 10-year guarantee on the internal primary heat exchanger.

This boiler has a smart LED digital control panel in a unique-looking circular design.

Worcester Bosch Greenstar 12Ri Boiler (91.79%)

The smallest of the boilers ranking so far, the Worcester Bosch Greenstar 12Ri boiler measures 600mm x 390mm x 270mm. 

This model is ideal for those properties with minimal space as you could easily tuck this boiler away behind a kitchen unit or under the stairs.

It comes complete with a guarantee of up to 10 years providing it is installed and maintained by a certified Worcester Bosch engineer.

This boiler is minimal in design featuring a very unobtrusive white gloss finish and simple boiler control knob.

Worcester Bosch Greenstar 15Ri Boiler (91.72%)

If you liked the sound of the Worcester Bosch Greenstar 12Ri boiler but know your property needs a little more power, you should consider the Worcester Bosch Greenstar 15Ri boiler.

It’s exactly the same in dimensions and aesthetic finish, but has a higher output level so you have more hot water power.

It measures in at 600mm x 390mm x 270mm so could easily fit within a small cupboard but always check your dimensions first.

As with the other Greenstar boilers, it comes with a guarantee of up to 10 years – providing you follow the servicing and installation requirements.

Best choice central heating boilers for a 2-3 bedroom house

If you have a mid-sized home with 2-3 bedrooms, you are likely to need a boiler with an output of 28kW to 34kW.

According to our system, the four best boilers of this output range are all Baxi models, followed by a Worcester Bosch. 

Currently, there are 126 boilers in this group on the market in the UK and the average price is £1,008.

Baxi Platinum 28kw Boiler (92.36%)

As with our results for the first group of boilers, the Baxi Platinum range comes in first place. 

The Baxi Platinum 28kw boiler is slightly on the large size, measuring 780mm x 450mm x 345mm but is still your traditional wall-hung unit. 

It rates highly due to its 10-year warranty, energy efficiency rating, and affordable price. 

As with other models in the Baxi Platinum range, it benefits from front access to all parts of the boiler. 

This means you don’t have to leave space around it for engineer access during your annual service, and it’s much less messy to upkeep if you need a part replaced. 

Baxi EcoBlue Advance 28kw Boiler (92.18%)

Coming complete with a 10-year guarantee, the Baxi EcoBlue Advance 28kw is a sensible choice for a mid-sized home and itslengthy guarantee will provide you with extra peace of mind.

The dimensions of this boiler are 763mm x 450mm x 345mm and it is finished with a durable white coating and concealed control panel. 

As with the entire Baxi range of boilers, this is manufactured in the UK and benefits from high-quality brass internal components for longevity. 

Baxi Platinum 33kw Boiler (92.18%)

Featuring heavily on our HomeSage boiler charts, the Baxi Platinum range comes into play once more with its 33kW size model. 

It measures 780mm x 450mm x 345mm and is sturdy, durable and benefits from a scratch-resistant white gloss finish. 

It is a front-access boiler so once it’s been installed it’s easy for engineers to service and repair your boiler if necessary. 

This boiler would suit a home with a high water demand as it has a good flow rate of 13.5 litres per minute.

Baxi EcoBlue Advance 33kw Boiler (91.94%)

The Baxi EcoBlue Advance 33kw boiler scores slightly lower than the Baxi Platinum due to its slightly more expensive price tag. 

It measures 763mm x 450mm x 345mm so is marginally smaller than the Platinum model but has the same water flow rate of 13.5.

You are more likely to save extra pennies with this boiler because, as with the 24kW model in this range, it is compatible with the uSense smart control thermostat system.

This means the boiler adjusts to the property’s temperature so you’re not overpaying to heat when you don’t need to be. 

Worcester Bosch 2000 30kw Boiler (91.62%)

This boiler is a competitively priced unit suitable for a mid-sized home. It measures 724mm x 400mm x 300mm so is relatively compact in size. 

It is the quietest combi-boiler available from Worcester Bosch.

The Worcester Bosch 2000 30kw comes with a 5-year guarantee out the box as standard, providing you register the boiler online within the specified time frame. 

You can upgrade this guarantee to 6 years when you install it with the Greenstar System Filter and the primary heat exchanger comes with its own separate guarantee of 10-years. 

It has a smart, modern finish with a quirky cyclical control panel dial. 

Central heating boilers to think about for a 4+ bedroom home

If you have a large property, for example a detached 4+ bedroom home and 2-3 bathrooms, you will require a boiler with an output of 35kW+. 

The average price for these boilers is £1,528 and currently, there are 80 models to choose from in the UK.

Baxi 636 Boiler (92.43%)

The Baxi 600 range is compact in size but big in power.

This particular model measures in at 700mm x 390mm x 285mm so has a compact cupboard fit. 

It comes with a 7-year warranty, so not quite as high as other Baxi boilers, but still a considerable amount of time for peace of mind. 

It’s an exceptionally light boiler which makes for an easy installation and only weighs 29.5kg.

The Baxi 636 has a digital LED screen alongside two easy-use control knobs.

Baxi EcoBlue Advance 40kw Boiler (91.80%)

Featuring a high output of 40kW and a generous 16.4 litre per minute flow rate, the Baxi EcoBlue Advance 40kw is a solid choice for a larger home with high water demands.

The dimensions of this boiler are 763mm x 450mm x 345mm and it weighs 39kg.

It comes with a 10-year guarantee as standard, is Energy Savings Trust endorsed and also meets the minimum energy efficiency rating required for the Boiler Plus compliance. 

To get maximum efficiency from this boiler, you can combine it with a Baxi Time and Temperature control. 

Baxi Platinum 40kw Boiler (91.50%)

The boiler with the highest output in the Platinum range – the Baxi Platinum 40kw has an impressive 16.4 lpm flow rate alongside a 40kW output. 

The dimensions of this boiler are 780mm x 450mm x 345mm and it benefits from an intelligent heat system which automatically adjusts the output to save you money on your energy bill. 

It has a stainless-steel heat exchanger and the boiler comes with a free 10-year warranty, providing you follow the terms and conditions.

This boiler features the smart chrome trim of the Baxi Platinum design and the control panel is disguised by a fold-down cover for minimal aesthetic disruption. 

Worcester Bosch Greenstar 8000 Life 35kw Boiler (90.49%)

The Greenstar Lifestyle range from Worcester Bosch are the newest models by this manufacturer and benefit from a range of advanced technological features for maximum efficiency. 

This model measures 824mm x 440mm x 364mm so certainly one of the larger boilers ranking on our scoreboard. 

It is the direct replacement for the multi-award winning Greenstar CDi classic boiler and features a reduced weight compared to the older model – the Greenstar 8000 Life 35kw weighs 53kg.

This boiler has a Greenstar Intelligent Filling System which eliminates the need for you to manually refill the boiler, saving you time and energy.

Worcester Bosch Greenstar 36CDi Compact Boiler (90.45%)

Although this boiler is compact in size, measuring just 690mm x 390mm x 280mm, it is not lacking in output power, flow rate or advanced features. 

The Worcester Bosch Greenstar 36CDi is a compact boiler suitable to heat a larger home with minimal wasted energy as it has an exceptionally high energy efficiency rating of ‘A’.

This boiler has a traditional white finish and a fold-down control panel cover which is user-friendly and features a range of different controls for your convenience. 

Worried about water pressure?

Although most properties benefit from using a gas combi central heating boiler, sometimes a system boiler is the best choice – especially in areas of low water pressure.

Here, we have ranked the top 5 system boilers available in the UK as of 2021. 

Worcester Bosch dominates our results with their Greenstar range of system boilers thanks to their affordability and high efficiency ratings.

We recommend you speak to an installer to find out if a system boiler might be the best choice for your property. 

Save up to 54% of your boiler installation with HomeSage

You can save up to 54% of the cost of the supply and the installation of your new central heating boiler by filling in your details on our online form.

We will contact three or four local, trusted and Gas Safe regulated engineers with your query who will get in touch with you for a free quote and any relevant advice. 

Our service is completely free for you and it is no obligation no matter what you decide to do.

If you want to find out more about boilers, you’ve come to the right place – check out our Advice Hub for our latest blog posts, or take a look at our comprehensive guide to new boiler installation here.