There are two ways to answer the question of what is the best boiler on the market.
One, from the point of the consumer.
Two, from the point of the installer.
From the point of the consumer:
Which? will tell you the Worcester Bosch range are the best. They are good and British Gas have invested heavily in them, and have buying power beyond that of any other company, which means for the end user, when they make offers like £400 off they are still making over 100% mark up on the boiler itself, whilst the smaller companies and one-man bands/sole traders pretty much get the same online prices that the end user does.
There is therefore, a level of perceived reputation simply through buying power and marketing budget through investment. Capitalism at its finest!
The boiler itself is full of small water ways and plastic. Therefore, like any installation a flush is required to the relevant British standards but with a Worcester I would always recommend a power flush and of course a magnetic filter– The Calmag and Fernox ones I believe are superior.
On a combination boiler I would also recommend a scale reducer. These preventative measures cost no extra labour (well certainly no extra labour cost where Marvel is concerned) and will always ensure that should future problems arise, the manufacturer can not wiggle out of paying.
Personally, I would Install a Vaillant. Better quality and parts and the current generation Is excellent. 8-year warranty/peace of mind is also as standard for customers of advance installers.
You may think that answers the next part of the question.
From the point of the installer:
However, the most technically advanced boiler I have seen with the highest efficiency rating on hot water mode is the Intergas HRE range launched in May 2018 in the UK. One of my previous blogs was about the Boiler Plus scheme – the UK government is introduced from April 6th 2018. This involves adding one of four different controls to improve efficiency of the home heating system further. All of these controls are outlined in our blog here.
The Intergas has two of these controls already built in – The heat recovery and the weather compensation. The further external smart stat is one that can be controlled via a smart phone and even remotely by the installer on a separate interface. In the future I believe this is an absolute game changer.
Effects of Changes
These changes to the boiler also mean the flue is central and the elbow doesn’t terminate in the wall. This makes it easier to install, and these adaptations remove the wariness engineers have previously had in installing these boilers. There is also a simple bracket and normal tails, no jig. The expansion vessel even disconnects from the top – which makes servicing / replacement a lot quicker and effective.
Intergas are gradually building a greater market share in the UK and are currently huge in the Netherlands, Germany and Canada. As consumer confidence grows and as the Intergas brand and reputation develops I have no doubt these will become more of a house hold name.
You cannot beat quality. The heat exchanger itself has 22mm water ways and a separate loop for DHW so no need for a separate lower heat exchanger. This means the hot water can work even if the system pressure is zero, and there are less moving parts to go wrong, or be replaced.
Intergas, Vaillant then Worcester for me. This is of course my own opinion.