Worcester Bosch, Vaillant, Baxi and ATAG — compared on what actually matters over fifteen years: warranty, efficiency, hot-water flow, noise and the size it needs to fit. No prices, no pressure. Just the facts, from an installer who fits all four.
Every figure here is from the manufacturer's own documents. How we sourced them
There is no single "best" boiler — only the best boiler for your property, your hot-water demand and where it has to go. A flat with one bathroom and a big family home with three are two entirely different problems. This tool lets you put the ranges side by side on the measures that decide it, so you can see the trade-offs for yourself.
Pick a boiler type to begin, then pick up to three brands and compare their models side by side.
Select up to 3 to compare.
There is no single “best” boiler — only the best one for your property, your hot-water demand and where it has to go. Answer three questions and we’ll narrow 62 models down to the two or three worth looking at, with the trade-offs spelled out. Nothing is submitted and nothing is stored.
A combi heats water on demand from the mains — no cylinder, no loft tank, compact, and ideal for flats and homes with one bathroom. A system boiler works with a hot-water cylinder (like a Megaflo), delivering strong hot water to several bathrooms at once — the right answer for larger homes. A heat-only (regular) boiler suits traditional systems with a tank in the loft. Get this wrong and no amount of warranty or efficiency will fix it.
Measured in litres per minute, flow rate is how much hot water reaches the tap. It's the number that decides whether two showers can run at once. For a combi, a higher flow rate matters more than raw kW in a busy home — though beyond a point, a system boiler and cylinder is the better answer than an ever-bigger combi.
A long warranty is a manufacturer betting on its own reliability. But read the conditions: most require registration within 30 days, annual servicing by a Gas Safe engineer, and — for some brands — installation by an accredited installer. The headline "up to X years" isn't always the figure you'll actually get; it depends on who fits it and how it's set up.
The most-overlooked spec, and often the deciding one. A boiler has to physically fit the space — and it needs clearance around it for the flue, for servicing, and to meet the manufacturer's rules. A unit that fits a kitchen cupboard on paper may not once clearances are added. This is where an installer's eye beats a spec sheet, and it's why we survey before recommending.
Every new boiler sold is A-rated (around 92–94% ErP). The difference between two quality boilers is a few pounds a year — far less than the difference a correctly-sized, well-installed system makes. Don't choose on the second decimal place of efficiency; choose on fit, flow, build and cover.
Compare all you like here — then, when you want a straight answer, Ravinder will survey your home and tell you which boiler is right for it. No sales pitch, no obligation.
DGN GAS · London-wide boiler installation · Gas Safe registered (domestic & commercial). Boiler specifications and warranties change; this comparison is reviewed periodically.
The table tells you what the boilers do. It can't tell you which one suits your pipework, your mains pressure or how many bathrooms you run at once — that needs someone to look. Send the basics and we'll come back with the two or three worth considering, and roughly what they cost fitted. No obligation, and we won't chase you.