Best Combi Boilers in the UK (2024): Reviews & Buying Guide

To properly assess the boilers we mention, we checked professional reviews, feedback from consumers, and awards and accolades the company or their products have received. By comparing these points, from combi boiler reviews from customers and installers, researching award-winning brands and making a market price comparison, we believe we’ve found some of the top-rated boilers available to install today.

When looking at reviews, you first need to consider the output power and the efficiency of the system, as these will have the biggest impact on your home’s heating and hot water supply. Other factors to consider include the brand reputation, the fuel it uses, the warranty, and the price.

If this all seems overwhelming, don’t worry! We’ve squashed all these categories into easy-to-follow guides below so you can find just what you need.

We know how frustrating it can be to find the answers you want quickly and simply, that’s why we’ve taken the time to find the best combi boiler for different circumstances. No two homes are the same, and your demands for hot water and heating are important.

To find the best combi boilers, we looked at a range of categories and compared boiler models on offer from some of the best-recognised brands on the market. We wanted to find out which brand offered the best for customers, as well as the reputation of each model.

To further narrow down our search, we looked at the following criteria:

Each model has something unique to offer, so to help you make a decision we’ve broken down their key features and costs in the following sections in more detail.

Baxi Platinum Compact combi

Estimated price (Exc. installation): £1,300 - £1,700

Gas boilers are the most popular choice among UK homeowners. Figures show that approximately 81% of homes in England, Scotland, and Wales are connected to the gas network, with the vast majority using gas boilers. As combis are the most common type of boiler across the country, it’s no surprise that there are many gas combi boiler options around.

For homes not connected to the grid, oil or liquefied petroleum gas (LPG) are the most common options for fueling their boilers. Electric boilers are another great alternative, with better environmental benefits if paired with a renewable energy source. They are, however, usually more expensive to run due to higher electricity prices.

Electric combi boilers don’t waste energy or release CO2 when working. However, they can only achieve zero emissions when the electricity powering them comes from renewable sources, such as solar panels.

The best electric combi boilers don’t waste energy at all, as they boast efficiencies of up to 100% but these boilers may not necessarily save more than gas boilers (especially in regions where electricity is more expensive per kWh). One model we highly rate is the EHC Mercury combi, it’s up to 100% efficient, can heat central and underfloor heating and comes in outputs suitable for small to medium-sized homes.

It’s worth remembering, however, that unless you run an electric boiler on a free, renewable source (like domestic solar panels), they can be expensive to run given fluctuating electricity prices.

From an environmental perspective, we can draw some conclusions on the impact of each type of combi boiler based on the fuel they use.

When looking for a combi boiler, your first indication of quality will be to check the length of the manufacturer's warranty or guarantee. We always recommend this because the more time a brand is willing to protect their product for free, the more likely it is to last! (why else would they be so generous?)

That’s not all you want to look out for, though. You can also check customer reviews to see how well these products perform over time and look for special selling points, such as ‘stainless steel heat exchangers’. It might not seem like much, but opting for stainless steel can mean a long-lasting, higher-performing boiler.

We’ve listed some of our picks for the best combination boilers you can rely on for years.

If you do some shopping around for the best combi boiler on the market, it won’t take long before you run into a Worcester Bosch - and with good reason!

This boiler brand has a great reputation for long-lasting, award-winning products. We’ve opted for the Greenstar 8000 Style combi here because of its fantastic features. With its large output range, this model would be the best combi boiler for a 3 bed house.

It comes with a warranty of up to 12 years, an efficiency rate of 94% and a range of outputs to suit both small and large homes - meaning it ticks a lot of boxes. Not only can you count on it for at least 12 years without the worry of any breakdown costs, but it’ll also save you money with its high efficiency and optimal size range. Plus - it looks pretty stylish!

Customers give Worcester Bosch a generous 4.6 out of 5 on Trustpilot, rating them ‘Excellent’ for over 40,000 reviews. Reviews range from excellent customer service to quick, quiet, efficient boiler models.

Another top contender if you’re looking for the most reliable combi boiler is the Vogue Max from Ideal Heating. This sleek model boasts the all-important stainless steel heat exchanger, which ensures high corrosion resistance and flawless performance throughout its lifetime.

In addition, Ideal offers a 10 to 12-year warranty for added reliability and security. Ideal prides itself on using premium materials and includes details to ensure your boiler lasts. For example, the Vogue Max also includes frost protection and the Ideal system filter to protect your heating from day 1.

With a high efficiency of 93% and smart compatibility, you can easily control this boiler to help optimise your heating, reduce energy waste and save money on bills.

Customers give Ideal Heating 4.8 out of 5 on Trustpilot, an ‘Excellent’ rating from over 40,000 reviews. Customers commented on the excellent service and helpfulness of their engineers, and how quick these models are to fit and fix.

Viessmann is another highly acclaimed brand, with a well-earned reputation for long-lasting boilers. The Vitodens 100-W combi boiler comes with a 10 - 12 year guarantee option, a stainless steel heat exchanger and a highly efficient, low pollutant burner (the MatriX Plus). The Vitodens also won the 2019 Design Plus Award for it’s fantastic features.

With a range of output sizes, this boiler can serve homes with as few as 10 or as many as 20 radiators, and up to 2 bathrooms. With its A-rated efficiency, it will also waste less fuel and save on energy bills. It also comes in as one of the best compact combi boilers, great for saving space.

Customers rated Viessmann UK a 4.2 on Trustpilot, with just over 7,000 reviews (although the company does span many countries). Comments mention how these boilers surpass expectations, heat water super quickly and have a sleek design.

So far, we’ve looked at some premium boiler brands that offer some of the best combi boiler options on the market. With this high reputation, however, often comes a higher price tag and for many homeowners, that’s just not going to work. So, what are the best combi boilers for those on a budget?

Keeping in mind some of the key criteria that make a boiler great, we’ve found 3 combi boilers that can offer high performance and efficiency, but come in at the lower end of the price range. Generally speaking, looking for a boiler under £1,000 will limit your choices, and may be particularly difficult if you have a larger home which needs a more powerful boiler.

For our top picks, we’ve included boiler models in a range of sizes. This can affect costs, but we’ve included an estimated new boiler cost range to give you a guideline figure. Here are our picks for the best affordable combi boilers.

If saving energy, reducing CO2 emissions and protecting the planet are at the top of your priority list, then you should focus on finding the best energy efficient combi boiler. In terms of fuel type, the electric boiler is (numerically) the most efficient boiler, with 99-100% efficiency ratings - more than any gas or oil condensing boiler (although, consuming electricity can be more expensive, so it won’t necessarily reduce expenditures).

We know that gas boilers are the most common type of boiler in UK homes, but switching to an electric combi boiler could reduce your carbon footprint. This is because they turn 100% of the power from electricity into usable heat (i.e. 1kW of electricity equals 1kW of heat).

One thing you need to keep in mind, however, is that unless your electricity comes from a renewable source, there are higher costs involved - electricity generated from fossil fuels has a significant environmental impact and using more electricity will inflate your average bill costs.

It is possible to generate clean home heating with an electric combi boiler though, if you pair it with solar panels or other renewable energy sources, for example.

We looked at available electric boilers on the market today and chose our top pick to be the Electric Heating Company (EHC) Mercury combi boiler.

The reason we chose this model is because it offers a wide range of output sizes, making it suitable for different property sizes. It also comes with some great features that make it a firm contender against its gas or oil counterparts. Some of its features include:

Prices range from £1,530 - £1,850 (excl. installation)

If you’re not ready to make a full switch to a renewable energy source and are looking for energy efficient gas boilers, we’ve got that covered! Although most modern condensing combi boilers are around 90% efficient, some brands have created models that go even higher. The table below lists some of the most efficient gas boiler models, with an indication of their price range.

Boiler output, measured in kilowatts (kW), refers to how powerful the boiler is and how many radiators or taps it can supply with hot water. Output is often called ‘boiler size’ because the higher the output, the larger the home it is suitable for.

In basic terms, the more kilowatts a boiler has, the more hot water it can supply. It’s really important that your boiler size is right for your home - if it’s too low, you won’t get enough hot water for your needs, but if it’s too high, you’ll end up paying over the odds for the energy to fuel it.

With this in mind, we’ve summarised the correct output sizes below for you to consider. It is always recommended, however, that you get professional advice from a heating engineer before purchasing your boiler so that you get the right size for your unique circumstances.

When we looked at the best combi boiler models on the market, we noticed that there is a range of options available to suit most houses. Many of the boilers we have already mentioned offer different output sizes that make them great for different homes.

If you have a small flat or 1-bedroom apartment, with 1 bathroom, you will want to look for a smaller-sized boiler (in terms of water output). The fewer radiators and taps/outlets your home has the less oomph your boiler needs.

Fortunately, some of the best boiler brands do offer models that come in lower output sizes, or which can be adjusted to suit your needs. During our research, we found that the best small combi boiler model was Vaillant’s ecoTec Plus 825.

This boiler has a CH output between 4.2 - 20.4kW and a DHW (domestic hot water) output of 25.4kW, making it perfect for the smallest of spaces. It also comes with Vaillant’s signature features like A-rated, 94% efficiency, ultra-quiet (award-winning!) operation and up to 10 years guarantee. Like all Vaillant boilers, it’s also ready for a 20% hydrogen gas blend for future environmental protection.  Prices range from £1,200 - £1,400.

Of the models included above, there is a range of prices based on the size of boilers available. Each product is an example of one of the best boiler brands currently on the market and, as you may expect, the more premium the brand the higher the costs will rise.

The good news is, however, that many of these brands do now offer lower-cost alternatives - particularly some of the Baxi and Ideal ranges - which are worth looking into.

If you are on a limited budget, or looking for a cheap boiler installation but want to get the best possible option, we recommend you check the models available from Baxi. They currently offer a range of combi boilers that offer you more features the more you pay, which is good for those looking for low costs and no-frills.

No matter which boiler you look at though, be prepared to sacrifice features the cheaper you go - for example, warranties will often be much shorter on cheaper products.

Here is a look at one of the cheaper Baxi combi boilers:

Baxi 200 series

Estimated price (Exc. installation): £650 - £900

The best combi boiler can vary based on your specific needs and budget. From our research, the Viessmann Vitodens is the best from a price, features, and efficiency standpoint. Aside from its fantastic on-paper specs, it has garnered acclaim as a Design Plus Award winner in 2019.

There are also many other options that also hold promise. For affordable options, the Baxi 200 can be a great low-cost system. Available for as low as £650, it’s a budget option with a great reputation and decent performance.

As a non-gas alternative, the Electric Heating Company (EHC) Mercury is the most efficient electric combi, offering 100% efficiency and easy installation. This model can be the best option for homes outside of the gas grid.

Ultimately, what boiler is best for your home can vary based on your needs. Whether that involves lower cost, better performance, or alternative fuels, there are many options on the market.