The Worcester Bosch Greenstar 4000 15kW System Gas Boiler is a condensing system boiler for small to medium homes with up to 10 radiators and 1-2 bathrooms, requiring a cylinder. It provides a 15kW output and a 94% efficiency rating (ErP A-rated). Measuring 710x400x330mm and weighing 33kg, it’s cupboard-friendly. It includes a 1:10 modulation ratio, a stainless steel heat exchanger, and EasyControl. It supports natural gas and offers a 7-year warranty, extendable to 10 years with a filter and Excelerate installer. Suited for moderate demands.