Worcester Bosch say the Greenstar 4000 has now passed one million boilers sold. That is a factory milestone from July 2026. It is not, on its own, a reason to change your heating.
What it tells us locally is simpler: this is a very common wall-hung gas boiler in smaller homes and flats. We see 4000s on jobs around Marlow. Parts are easy. The case is familiar. The guarantee still depends on a yearly Gas Safe service and on the boiler being registered.
If you have a 4000 that is in lockout, losing pressure or making a noise it did not make last winter, treat that as a service or repair question, not as a statistic. If you are replacing an older Greenstar and a 4000 is on the quote, ask why that output was chosen for your house, not whether a million other people bought one.
We can service a 4000 we did not install. Call 01628 901902.