Worcester Bosch and Viessmann both occupy the premium tier of the UK gas boiler market. Both are excellent choices — but they have different strengths.
Efficiency
Viessmann Vitodens 200-W: up to 98% ErP. Worcester Bosch Greenstar 8000: 95.3%. Viessmann wins on efficiency.
Warranty
Worcester Bosch: up to 12 years with accredited installer. Viessmann Vitodens: up to 10 years. Worcester wins on warranty length.
Build quality
Viessmann's Inox-Radial stainless steel heat exchanger is widely considered superior to cast iron or aluminium alternatives. Viessmann wins on heat exchanger quality.
UK parts and service network
Worcester Bosch has the largest UK spare parts network of any boiler brand. Getting parts quickly is easier. Worcester wins on parts availability.
Price
Comparable Viessmann models are typically £200–£400 more expensive than Worcester Bosch equivalents. Worcester wins on price.
Our verdict
For the typical homeowner: Worcester Bosch Greenstar 8000. It's slightly cheaper, has a longer warranty, and better UK service support. For the homeowner who wants the very best engineering and efficiency, and is prepared to pay the premium: Viessmann Vitodens 100-W or 200-W is an exceptional boiler.