Combi boilers are the most popular type of boiler systems in the country. Most households value them for their ability to provide instant access to hot water for the tap and radiator simultaneously; without the need for a separate water tank.

Mains water feeds the unit, which is heated and sent to bath and sink taps, as well as heating units around the home. Once used up in the radiator, it circulates back to the boiler where it can be reheated.

These types of boilers are especially appropriate in smaller properties, as they save large amounts of space compared to older styles of boiler. They can also help with the strength of flow as the boiler doesn’t rely on gravity bringing hot water down from a loft-based storage tank.

The Best Combi Boiler for your Property

Before you make the decision to invest in a combi boiler, consider the factor of the number of users, as well as your budget and priorities. If you have a large household, only one outlet can reasonably be used at the same time – so one person couldn’t shower while another washed their hands. Also, if your mains pressure is weak, it might not be the choice for you.

What’s more, combi boilers can set you back quite a lot of money. Replacing a standard boiler with a new combi might cost you just under £3,000 (prices can range anywhere from £400 to £2,000 for the unit itself, but you’ll need to factor in installation costs too).

Although an experienced plumber or heating engineer can advise you on model and brand, it does make sense to have an understanding of what’s out there on the market. Let’s take an in-depth look at the market’s best combi boiler options then, shall we?

Worcester Bosch

The Worcester Bosch Greenstar Pro 25i is among the most efficient equipment available. It boasts 94% efficiency and offers a flow rate of 9.8 litres per minute of hot water. This is in-line with many other Worcester Bosch models, but the Pro 25i is one of the best value from the range, with a price of £875 and seven-year guarantee.

This boiler is perfect for 1-2-bedroom flats, though would suit somewhere with more space, as it is not a compact boiler that would fit neatly into a kitchen cupboard.


As a brand, Valliant has been awarded the Quiet Mark accreditation by the International Eco-Award Scheme. Its EcoTec Plus 825 is a model comparable to Worcester Bosch’s Greenstar 25i and has similar features overall, other than a slightly higher price tag – at approximately £1,100 – 5-10 year guarantee, and compact body to fit in a cupboard.

If you live in a large house with at least five inhabitants, Valliant is definitely the brand of choice – their ecoTEC Green iQ 843 is 94% efficient and has a 17.8 litre-per-minute flow rate. It’s available for around £1,980 and comes with a 7-10-year guarantee.


Hoping to save money in your first home? Houses with two beds are the perfect location to install the Ideal Independent C30 – with a cost of only around £650, but a flow rate of 12.3 litres of hot water per minute. You’ll be pleased to know this Ideal boiler also comes with a five-year warranty, so you can count on its value for money.

Glow Worm

The Glow Worm Ultimate 2 is another excellent affordable model suited for smaller houses. The boiler itself costs just under £700, with a five-year manufacturer’s warranty. This Glow Worm boilers’ output is 25KW and puts out 12.5 litres of hot water per minute, with an efficiency of 89%. This option is high-performance and high-efficiency, keeping long-term costs down as well as your initial layout.


Baxi is part of one of Europe’s largest water and heating manufacturers, and also one of the longest-serving partners. Its specialism is low-carbon options, and its boilers are relied upon by owners of medium to large homes. The Platinum 40 is a premium model, priced at £1,225, that brings high efficiency and output – at 89% and 16.4 litres per minute respectively – as well as a 10-year warranty as standard.


Focusing on energy efficiency and product reliability, Atag is a European company that produce some brilliant boiler models. The iG Economiser range, their most recent innovation, are extremely efficient, come with a 10-year warranty and recycle all residual heat back into the boiler unit to save what would normally be wasted, and cut costs.

The Economisers are user-friendly, and the proprietary heat exchanger has a lifetime replacement guarantee meaning the boilers stay cost effective for much longer. Whilst these quality boilers might not be cheapest, the Atag range is forward-thinking, built to last, and incredibly effective.

If you’ve found the combi boiler you need to save you space and money, then Invictus Mechanical is the experienced partner you need to complete any replacements and installations. Since 2016, we’ve worked across Bristol and the Southwest, bringing cost-effective, hands-on support to business and homeowners.

Contact us today about all your boiler servicing and maintenance requirements.