Aside from being told you need a new roof, the words homeowners least want to hear are: “You’re going to need a new boiler”.
We dread the expense and inconvenience of having this essential item replaced and, with the cost of living soaring, the last thing we want is to shell out a huge wad just now.
But what if getting a new combination boiler was actually going to save us money in the long term? Ah, you’re starting to warm (ahem) to the idea now, aren’t you? Well, buckle up, because today’s models are not only leaner and meaner, they run more efficiently than ever.
What is a combi boiler?
The most common type of boiler in the UK, a combination boiler – or combi boiler for short – is connected directly to the mains water supply into your home and heats water on demand when you turn the hot-water tap on. They also heat the water that is circulated around your radiators.
They’re popular because they supply instant hot water, don’t take up a lot of room and, due to their prevalence, are easy to find repair and servicing contracts for.
On the downside, if you have a large home with multiple bathrooms, they generally can only produce hot water for one bath or shower at a time; they’re at the mercy of your house’s water pressure – so low water pressure means you won’t get a gushing flow out of your taps – and as they have so many bits inside them, there’s a fair amount of break-down potential.
What else do I need to know?
The average combi boiler will give good service for up to 15 years and, if you were to replace one now, would cost you anywhere between £500 to £1,800, plus installation charges.
Something useful to know is what a heat exchanger is. It’s a coil of pipe over which hot flue gasses are passed heating the water inside as it passes through.
Don’t go buying the most powerful one out there. Rather, get one that’s the right size for your home.
It is measured in kilowatts (kW) and depends on how many radiators, showers and bathrooms that you have. For one bathroom, look out for 26kW at minimum, 30kW for two, 35kW for three, while larger homes with more than three bathrooms will be better off with something larger. Do listen to the specially trained person you’re going to hire to install it, as they will be able to perform a heat-loss calculation of your property and then best guide you to the right size.
Quick tips
- Less than 10 radiators: get one that’s less than 27kW
- 10-15 radiators: get one that’s between 28 and 34kW
- More than 15 radiators: get one that’s over 34kW
Best combi boilers at a glance
- Best for efficiency and reliability: Vitodens 050-W - £1010.39, City Plumbing
- Best for houses with three bedrooms: Vitodens 100-W - £943.19, City Plumbing
- Best for small to medium-sized homes: Worcester Bosch Greenstar 4000 - £1474.98, Toolstation
- Best for if you have more than one bathroom: Worcester Bosch 8000 Life - £1964.39, City Plumbing
- Best for low energy consumption: Vaillant ecoTEC plus - £1529.99, City Plumbing
- Best for eco-friendly efficiency: Vaillant ecoTEC exclusive - £2350.91, Travis Perkins
- Best for buying on a budget: Glow-worm Energy 18kW System Gas Boiler ERP - £1124.39, City Plumbing
- Best for a good price for the size of boiler power: Glow-worm Energy Combi - £1294.79, City Plumbing
The main thing to bear in mind is that these days combi boilers are being manufactured to be as efficient and ‘green’ as possible, so you’re likely to get one that works harder for less money than whichever boiler you’re having to replace.
The Energy Saving Trust reckons you can save around £305 a year if you fit a new boiler, and that’s at pre-energy-crisis prices. Just imagine how much you could save now.
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Vitodens 050-W
Best for: efficiency and reliability
Want a sensibly priced, well-made combi boiler you can have installed and then just forget about for the next decade or so? This is the one.
Manufactured by German boiler giant Viessmann, it’s rated consistently highly and was the Which? Best Buy Gas Combi Boiler September 2021. It also has some very cool features. For instance, it’s so quiet you could have it in your living room and not notice it. Plus, it has a patented stainless steel Inox-Radial heat exchanger that converts the energy it uses into warmth.
The unit loses almost no heat itself, meaning it’s not just good for the environment, but saves you money as well. It has an energy related products (ErP) rating of 92 per cent, which makes it A rated. Finally, it comes with a three-year comprehensive warranty, which will be extended to 10 years if you have it installed by a Viessmann-trained installer.
Buy now £1010.39, City Plumbing
Vitodens 100-W
Best for: houses with three bedrooms
This boiler comes in various versions, including a heat-only boiler, so you can make sure you’re getting the right one. And, like all Viessmann-built boilers, this one’s three-year comprehensive warranty extends to 10 years if you have it fitted by a Viessmann-trained installer.
It’s also A rated, so you know it’s efficient and as good for the environment as possible. And like other Viessmann-built boilers, you can download the app and then control your boiler from anywhere on your phone, which is pretty cool. It features a patented stainless-steel Inox-Radial heat exchanger, which ups the efficiency, and has an LCD touchscreen display. This is the Vitodens to get if you have a larger home.
Buy now £943.19, City Plumbing
Worcester Bosch Greenstar 4000
Best for: small to medium-sized homes
Worcester Bosch boilers score consistently highly with both consumers and with award givers, making them one of the UK’s favourite boiler brands and this model is its top-seller.
It’s available at two kilowatt levels: 25 and 30kW, so suitable for small and medium-sized homes. It also comes in two colours, white and black, so you can match it to your decor. It has a number of clever features, including being able to control it over WiFi and smart tech that will turn it off if the water pressure gets too low and then turn it back on once it’s refilled the system.
It comes with a five-year manufacturer’s warranty or 10 years if you get a Bosch-accredited installer to put it in for you.
Buy now £1474.98, Toolstation
Worcester Bosch 8000 Life
Best for: if you have more than one bathroom
Like many top-of-the-range modern combi boilers, you can sync this designer’s choice through its Bosch EasyControl, which lets you take charge of it from anywhere. It’s also compatible with Amazon Alexa and Google Assistant – and you thought those were just for telling you the weather…
It’s a popular choice for larger homeowners for good reason, as it’s ErP rated 94 per cent, a high number that tells you it’s just about as green as a boiler could be. It comes in four kilowatts all the way up to 45kW.
This baby comes with a whopping 12-year guarantee provided you use a Bosch-accredited installer to put it in for you. And, if you ever do need parts, as it’s manufactured in the UK, they’re easy to come by.
Buy now £1964.39, City Plumbing
Vaillant ecoTEC plus
Best for: low energy consumption
The clue is in the name, which is why this combi boiler is rated A for efficiency and has a clever pump to reduce energy consumption and lower output when it’s in standby mode. It’s also quiet, with something called a Quiet Mark, which means it’s been tested and meets an independently certified standard to reduce noise in our homes.
It also has an easy-to-use display, a bonus as far we’re concerned, since standing in front of an appliance trying to work it out is never fun. It comes with a two-year warranty that can be extended to five years if you have it fitted by a Vaillant Advance installer.
Buy now £1529.99, City Plumbing
Vaillant ecoTEC exclusive
Best for: eco-friendly efficiency
If you’re serious about saving the planet, and you have deep pockets, this could be the combi boiler for you. Vaillant even hails it as its best boiler for performance, control and efficiency.
It can be controlled through an app, so you can turn the heating down even when you’re out of the country, and it carries Vaillant’s Green iQ mark, which means it’s the top one for energy efficiency. It’s so green, in fact, that an astonishing 85% of the boiler’s parts are recyclable.
Finally, it’s Quiet Mark accredited, so there’ll be no background hum to drive you nuts. It come in two kilowatt sizes – we’ve given the price for the 35kW version. You also get a 10-year guarantee if you use a Vaillant Advance installer.
Buy now £2350.91, City Plumbing
Glow-worm Energy
Best for: buying on a budget
This 18kW compact model is the budget buy of combi boilers and the one to get if you have a small place. For all of its cost-of-living-crisis credentials, it’s still A rated when it comes to efficiency, runs quietly and is great value for money.
It’s also easy to use and has a high-quality aluminium heat exchanger. It comes with a five-year guarantee, but use one of the Glow-worm Club Energy fitters and you can have a 10-year guarantee for nothing.
Buy now £1124.39, City Plumbing
Glow-worm Energy Combi
Best for: a good price for the size of boiler power
Meeting the ErP (that’s basically the green rating) for the EU as well as the UK, this Glow-worm model has an innovative and terribly efficient aluminium heat exchanger that promises a longer life than those with a copper or alloy one. You might like to know that it’s one of the brands that British Gas installs, which gives peace of mind.
You might also like to know that it’s made by Vaillant, Europe’s second-largest heating manufacturer. We’ve given the price for the 30kW version, but there are other sizes in this range. It comes with a seven-year guarantee that can be extended to 15 years if you use a Glow-worm Club Energy installer.
Buy now £1294.79, City Plumbing
