The Cheapest Combi Boilers in 2021

The Cheapest Combi Boilers 2021

Upgrading your boiler system certainly isn’t cheap, but the money you save in annual heating bills tends to offset cost in just a few years.

We believe you shouldn’t have to pay more than you need to for an energy-saving boiler.

With that in mind, we created this guide to the cheapest combi boilers in 2021 to give you further insight into your options.

We’ve ranked boilers in order of affordability and we’ll rundown of the best value boilers’ individual specifications and features so you can make the right choice for your budget.

Researching which combi boiler is going to suit your property and needs can be an overwhelming experience as there are so many things to think about. 

To give you a strong understanding of the combi boiler marketplace, we’ve taken a look at:

• what a combi boiler is
• choosing the right size combi boiler for your home
• why gas combi boilers are the best option
• the 10 cheapest combi boilers available
• the five best value combi boilers for a smaller property
• the cheapest combis for medium sized properties
• the most affordable combi boilers for a larger property

What is a combi boiler?

Combi boilers are the most popular choice of central heating systems in the UK because of their energy efficiency levels and affordability. 

Unlike traditional or system boilers which heat and store hot water internally, combi boilers draw water directly from the mains supply.

They heat the water as it passes through the system meaning that you always have access to a never-ending stream of hot water and heating.

They are usually wall-hung units and compact in size.

So much so that you can slot them in somewhere that works for your home aesthetic – often they are hidden behind a kitchen unit or under the stairs.

Combi boilers are energy efficient because they make best use of the energy they produce as a system so barely any is ‘lost’ to the boiler heating up the water.

For comparison, older, traditional boilers can often only be 75% efficient, meaning a staggering 25% of energy is ‘lost’ to the boiler just so it performs the task in hand.

This means you pay a lot less to heat your home using a combi boiler so your annual energy bill will be much lower.

The higher the energy rating your boiler has on a scale of ‘A’ to ‘G’, the lower you can expect to pay to heat your home. 

You can find out more information on combi boilers in our dedicated combi boiler article.

What is the best combi boiler for your home?

It’s crucial you choose a boiler with the right level of output (kW) for your property size and hot water needs.

This is because you gain maximum energy efficiency and low-cost benefits if your output is well matched to your requirements.

To work out how much your boiler will cost to run, you simply multiply the output by the cost of a unit of energy, for example a 18kW boiler fuelled by gas (priced at 4p a unit) would be 18 x 4 = £0.72.

We’ve compiled this table to give you an estimate into what size output of combi boiler you will require for your property:

It’s also necessary to take your property’s age into consideration due to the level of insulation it is likely to have. 

If you live in a modern home that was built after the year 2000, you most likely have a good level of insulation.

This means that you require a smaller boiler output than a property of a similar size but built in the 1950s.

For example, a pre-1900 3-bed and 2-bathroom property may require a 30kW boiler whereas a property of that size built after the new millennium would likely suffice with a 26kW boiler to retain the same amount of heat. 

When deciding on your new combi boiler you also need to consider the water flow rate which is the amount of water that can flow out of the taps within one minute. 

This is important because if two people turn a hot tap on at once, the pressure may up to halve for each individual. 

Remember that water flow rate is entirely dependent on the mains supply to your area.

Even if you opt for a boiler with a flow rate of 15lpm and the mains water pipes can only supply you with 10lpm, then 10lpm is the maximum amount available to you at one time.

Combi boilers have smaller dimensions than traditional boilers and they don’t require extra storage space in the loft for a water tank.

This makes them an excellent choice for properties that are lacking in space or which have converted their loft into an extra bedroom, for example. 

You may notice that some combi boilers benefit from generous warranty lengths.

This is because they are relatively straightforward in terms of pipework and internal components, compared to traditional or system boilers.

The more simple a device, the less things go wrong and, if they do go wrong, it’s quicker to diagnose and to fix.

This means that manufacturers can often offer more time on their warranties.

Why gas is better than electric, oil, or LPG

Although gas is the fuel supply of choice for most of the UK, there are four fuel options to choose from to heat your home. 

Most homes in the UK are connected to the gas mains which provides those properties with a constant supply of cheap fuel, it costs from just 4p per unit and you never have to worry about it running out.

Choosing to heat your home using liquid petroleum gas (LPG) can be an option if your home is not connected to the gas mains.

However, an LPG boiler requires the installation of a storage tank on your property.

A local supplier must also deliver regular top-ups of LPG – these may be disrupted in times of bad weather.

A similar fuel to LPG is heating oil which also requires a storage tank for your fuel.

Although this fuel is less expensive than gas, it is gradually being phased out of use in the UK due to environmental concerns. 

Electricity is the most expensive way to fuel your central heating although it can be easier to install these systems as they don’t require as much pipework.

This table gives you a clear indication of the cost of different fuelling sources.

However, to be fair, electricity boilers can perform the same job as a gas boiler using a lower output.

You may only need a 10kw electric boiler to deliver the same results as a 26kw gas-powered combi boiler. 

10kw at 16 equals £1.60 an hour – much lower than £4.16 but still much more than the cost of powering at 26kw gas-powered combi boiler for an hour.

Most installation companies recommend gas combi boilers for UK properties due to their energy efficiency, cost and space saving benefits and ease of installation. 

The top 10 cheapest combi boilers on the market right now

If you’re on a tight budget, there’s no reason to scrimp on quality when it comes to choosing a combi boiler.

We’re HomeSage and we want to help you make an informed choice when it’s time to upgrade your central heating system.

There are 206 gas combi boiler models available to purchase so we thought we would help narrow down your choices by rating available models by price, as the average cost in 2021 is £1,098.

We also have our own unique boiler rating system that takes the following into account:

• Boiler output,
• Energy efficiency rating,
• Price point, and
• Genuine customer reviews and ratings on Trustpilot.

This way, you can be sure you’re getting the boiler that will suit your needs – as well as your budget.

On the list below, boilers are listed by price only.

Honourable mentions

The 10 boilers finishing top on the HomeSage scoring system are…

As you can see, the highest ranking boiler on the HomeSage scoring system is £870 – nearly double what the cheapest boiler is but that’s still £228 cheaper than the average-priced boiler.

If you can find some extra budget, you would find that some of the above boilers will give you the best possible value for money, even if they’re not the very cheapest combi boilers.

The best value gas-powered combi boilers for a small property

For a studio apartment or 1-2 bedroom flat with 1 bathroom, a gas-powered combi boiler with an output of up to 27kW is usually recommended. 

There are currently 77 boilers in this category to choose from and the average 2021 price for a boiler for a small property is £1,035.

Please see our mini-reviews for the five cheapest, best-value combi boilers for smaller properties below:

Vokera Easi-Heat Plus 25Ci Boiler (82.21%)

The cheapest boiler for a small property is the Vokera Easi-Heat Plus 25Ci boiler and it measures in at 795mm x 405mm x 248mm. 

This boiler features anti-cycling control that prevents wasteful energy use from switching the boiler on and off and reduces wear and tear on your system. 

This model comes with a 5-year anti-scale warranty.

Glow-worm betacom4 24kw Gas Boiler (82.08%)

This boiler comes with a simple inbuilt analogue timer and it’s also compatible with the full range of Glow-worm controls such as the MiGo app which allows you to set your heating from your smart device.

It measures 740mm x 418mm x 300mm and features a smart chrome display panel that has a digital display and an easy-use control knob.

The Betacom4 is backed by a 5-year guarantee providing it is installed by Club Energy engineers and you join the Club Energy program. 

Ravenheat WH80 25kw Boiler (79.88%)

This Ravenheat boiler comes complete with a 5-year guarantee as standard for your peace of mind.

It boasts a large digital visible temperature adjustment display so it’s easy to keep your home cosy

It has been developed to be exceptionally quiet, so you won’t be disturbed by any bangs or bumps.

The Ravenheat WH80 25kw dimensions are 700mm x 400mm x 300mm.

Ravenheat WH90 30kw Boiler (79.88%)

The next step up for Ravenheat in our budget charts is the WH90 30kw boiler featuring a built-in deep seal condensation trap which reduces the chance of freezing pipes even in the winter months.

This wall-hung boiler measures 700mm x 400mm x 300mm so it is fairly compact in size. 

Featuring internal brass components, a 5-year warranty, and easy-to-use controls, this is a strong choice for a budget boiler.

Biasi Riva Plus ErP 24kw Boiler (76.15%)

The Biasi Riva Plus ErP 24kw measures 803mm x 400mm x 350mm so it’s slightly taller than the other budget boilers suitable for a small property. 

It has a very simple, pleasing white aesthetic to blend in with its surroundings and it features a concealed control panel.

It has built in frost protection so you can install this boiler into your garage without worrying over the winter. 

The best value gas-powered combi boilers for a medium sized property

If you’re considering a new combi boiler for a property of 3-4 bedrooms with 1-2 bathrooms but you’re on a tight budget, we’re pleased to present you with the five cheapest options available to you. 

You will likely need a boiler with an output of between 28-34kW and currently there are 80 of these on the market with an average price of £933.

Vokera Easi-Heat Plus 29Ci Boiler (82.15%)

The Vokera Easi-Heat Plus 29Ci has a very affordable price tag and an impressive grade ‘A’ energy efficiency rating.

Its features include a built-in digital clock with error code display to help solve any issues, and a hot water survivor function that eliminates the risk of no hot water even if the thermistor fails.  

This boiler measures 792mm x 405mm x 253mm and has a light lifting weight of 28kg. 

Biasi Riva Plus ErP 28 Bo (76.15%)

This boiler has a slightly lower efficiency rating at 88% and SEDBUK rating of ‘B’, however has a good flow rate and output kW.

It measures 803mm x 400mm x 350mm so relatively tall for a combi boiler. 

The features of the Biasi Riva Plus ErP 28 include a 24hr digital timer so you can set the heating for your preferred time of day or night easily.

It also features an anti-seizure routine that can help components from seizing up during periods of inactivity.

Glow-worm betacom4 30 Gas Boiler (81.98%)

As with the other Glow-worm boilers rated on our chart, the betacom4 30 gas boiler comes complete with a 5-year warranty providing it is installed by a Club Energy engineer and you follow all other protocols such as joining the Club Energy app.

The dimensions of this boiler are 740mm x 418mm x 300mm and it is compatible with a wide range of Glow-worm accessories for a stress-free installation. 

This boiler has a bright LED interface so you can see it clearly even in dimly lit areas.

Alpha EVOKE 28 Boiler (70.46%)

Featuring a newly designed stainless-steel heat exchanger, the Alpha EVOKE 28 is a front-access wall hung combi boiler measuring 712mm x 440mm x 255mm in size.

This is the smallest boiler available from Alpha and it boasts a comprehensive 7-year warranty and a backlit LCD display with push button controls and detailed operational information for ease-of-use. 

This boiler has a low electrical consumption rate so along with its grade ‘B’ SEDBUK rating, you can be sure to save some money with this budget boiler. 

Ravenheat CS90 30 Boiler (77.23%)

The final budget boiler for a mid-sized property is the Ravenheat CS90 30 which features an excellent grade ‘A’ SEDBUK rating, 5-year guarantee and ‘Whisper Quiet’ technology. 

The dimensions of this model are 700mm x 400mm x 300mm so fairly compact and could be tucked away out of sight if necessary. 

It has a very low lift weight of 29kg which will help with an easy installation. 

Combi boilers to consider for a larger property

Even if you have a semi-detached or detached home with more radiators to heat, there are a number of budget combi boilers on the marketplace with varying functions to fit your needs.

The boilers listed below would suit a 3 to 4-bedroom house with 3+ bathrooms. 

As of 2021, there are 48 boilers in this category and the average price is £1,357 and, below, we provide you with mini-reviews of the five least expensive options.

Ferroli Energy Top W60 Boiler (78.09%)

Featuring premix burner technology and outside weather control compensation, the Ferroli Energy Top W60 is an affordable choice for a larger home. 

It measures 945mm x 278mm x 440mm so is on the larger size of combi boilers and would need slightly more room than similar spec models from different manufacturers.

It boasts a high efficiency aluminium silica alloy heat exchanger complete with 31mm waterways which eliminates debris-related corrosion and hot spots so you have peace of mind knowing your boiler has longevity. 

Biasi Advance Plus ErP 35kw Boiler (78.36%)

The Advance Plus range from Biasi features cutting edge quad processor technology making them extremely reliable and efficient.

This model measures in at 700mm x 400mm x 290mm so it is fairly compact in size but certainly not lacking in features.

Complete with a 7-year warranty, this boiler has anti-frost protection and anti-seizure programming so, even after periods of inactivity, the boiler works smoothly. 

Ferroli Energy Top W80 Boiler (77.88%)

The dimensions of the Ferroli Energy Top W80 are 945mm x 278mm x 440mm 

This is an attractive wall-hung unit in a contemporary white shell featuring a digital LED backlit control panel.

This boiler has an exceptional 98% efficiency level.

With only 2% ‘lost’ energy, you will struggle to find a budget boiler that is as energy-efficient as this one.  

The slight drawback for this model is that it only has a 2-year guarantee as standard which is considerably lower than other combi boilers available on the market. 

Biasi Inovia ErP 35kw Boiler (80.75%)

This is a highly advanced boiler from Biasi, not only can it tell you the temperature of the water entering the boiler but also the DHW leaving the boiler too, as well as having a timed pre-heat option available for extra convenience. 

It can self-solve safety gas cut-outs and you can heat different areas of your home separately, for example underfloor heating can be set to a different temperature to your room.

The measurements of this model are 700mm x 400mm x 290mm and it has a 5-year warranty subject to terms and conditions. 

Ariston CLAS HE evo 38kw Boiler (77.97%)

With an energy efficiency rating of ‘A’, this boiler will certainly save you money on your heating costs.

The dimensions of this boiler are 770mm x 400mm x 300mm and it features a striking white and grey durable casing. 

It features an auto-diagnostic system which makes it easy to identify any faults and comes complete with a standard 5-year warranty that can be increased at an extra cost. 

This boiler is a solid budget boiler for a large property with increased hot water demands thanks to its high flow rate and output level.

Save up to 54% on your boiler installation with HomeSage

We offer a completely free, no obligation service to see if you could save up to 54% on the cost of the supply and installation of a new boiler.  

Simply fill in our online form and we will get in touch with three or four local, reliable and Gas Safe regulated engineers who will then contact you directly with a free quote to supply and install an energy efficient combi boiler system.

If you’re looking to save money with a value combi boiler, find out if you could save even more with HomeSage.