Greenstar 4000 Combi
A good combi boiler will deliver plenty of hot water for your showers, baths and sinks, and will keep your radiators piping hot throughout the coldest of winters
Read on to discover which brands make the most reliable combi boilers, and which our Which? Trusted Trader Heating Engineers think you should get.
Combi boilers are the most common type of boiler (Uswitch, 2021), with all the main boiler brands offering ones for you to install in your home.
Compare how the most popular combi boiler brands, from Ideal to Vaillant, stack up against each other according to the results of our 2021 boiler survey
Brand customer score
Brand engineer overall score
Typical price for a 30kW combi
£880 - £1,000
£700 - £990
£590 - £1,270
£650 - £1,350
£1,160 - £1,410
£780 - £1,280
£800 - £2,460
Reliability and brand customer score based on responses from 8,001 members of the public who've bought a boiler in the last six years, that took place in May-June 2021. Brand engineer score based on responses from 153 Which? Trusted Trader heating engineers in June 2021. Typical price range based on low and high prices for a standard 30kW combi boiler across the brand's range. A 30kW boiler is suitable for most medium-sized homes. Price doesn't include installation costs.
Our 2021 boiler survey of 8,001 members of the public, found 17 gas and oil boiler brands - all produce combi boilers.
Below you can find out a bit more about some of the most popular boiler brands* and their combi boilers.
*Brand popularity based on search volume from SEMRush in September 2021.
Baxi is one of the biggest combi boiler manufacturers in the UK. Its range of Assure, Duo-tec, Megaflow and Platinum combi boilers come in sizes to suit almost any size and type of home.
They range in price typically costing between £880 - £1,000 for a 30kW mediumm-sized combi boiler, although it has models starting from around £550.
Glow-Worm has several ranges of combi boilers including Energy, Essential, Betacom, Easicom and Ultimate.
Its combi boilers range in price, starting from around £560, with a medium-sized combi boiler usually being between £700 - £990.
Originally called the National Radiator Company, Hull-based Ideal has been around for 100 years. It has several ranges of combi boilers including Exclusive, Instinct, Esprit Eco and Logic+ ranges.
Its combi boilers come at a variety of prices, you can get a 30kW medium-sized boiler from around £590, going up to £1,270.
Potterton is part of Baxi, which is in turn part of the BDR Therma Group. As such, several of Potteron's ranges - such as its Assure range - have been absorbed under the Baxi name. It still owns the Titanium Combi, which costs around £800 for the 28kW size.
German manufacturer Vaillant is a large combi boiler manufacturer which has the ecoFIT and ecoTEC range of combi boilers.
They typically cost between £1,160 - £1,410 for a medium-sized boiler of 30kW.
Viessmann is a German boiler brand making waves in the UK boiler scene. Its Vitodens combi boiler lines have been updated in 2021.
They cost between £780 - £1,280 for a mid-sized 30kW boiler, and come in a large range of sizes to suit almost any home.
German manufacturer Worcester Bosch is one of the biggest combi boiler manufacturers in the UK.
Its combi Greenstar range starts at around £800 and goes up to around £2,500, depending on the size and hot water flow you need for your home.
To get the best combi boiler, it's crucial to go for a reliable brand that won't break down, and to get one that's the right size and fit for your home.
An unreliable combi boiler will fail early and is likely to result in regular costly repairs. On average, it costs almost £200 for a boiler repair (Which? survey, 2021). So it pays to invest in one that will last.
An oversized combi boiler will also lead to you spending more on your heating and hot water than you need to, and an undersized one will deliver a disappointing flow of hot water to your taps and radiators. The simplest way to estimate the size of boiler you might need is to count the number of radiators you have
This is a rough guide. A fully trained heating engineer will be able to more accurately size your boiler after a full heat loss survey of your home.
Proper installation is key to the ongoing health and efficiency of your combi boiler. Poor installation can lead to early failure, as well as money wasted on repairs and through having a heating system that isn't as efficient as it should be.
We'd recommend using a , too. They have all been vetted by a trading standards officer, and the satisfaction of their customers is regularly monitored to ensure they are the best of the best in their trade.
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