{"product_id":"worcester-greenstar-4000-21kw-system-boiler","title":"Worcester Greenstar 4000 21KW System Boiler","description":"\u003ch3\u003eWorcester Greenstar 4000 21kW System Boiler\u003c\/h3\u003e\n\nThe Worcester Greenstar 4000 21kW System Boiler is a reliable and efficient choice for medium to large homes, especially those that use a stored hot water cylinder. Designed to deliver consistent heating performance, this model balances energy efficiency with everyday practicality.\n\nIts compact, lightweight build makes installation straightforward, even in tighter spaces. The boiler comes with a built-in pump and expansion vessel, helping installers achieve a tidy and efficient setup. Homeowners can also enhance comfort and control through a wide range of optional heating controls, including modern smart thermostats for improved efficiency.\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\nCompact, space-saving design\n\nBuilt-in pump and expansion vessel\n\nOptional plug-in diverter valve\n\nCompatible with a wide range of optional heating controls\n\nIdeal for medium to large homes using a hot water cylinder\n\n\u003ch3\u003eTechnical Information\u003c\/h3\u003e\n\nManufacturer: Worcester Bosch\nModel: 4000\nMPN: 7733600383\nSKU: 79146\nGTIN: 4057749856722\nProduct Type: Gas System Boiler\n\nPerformance:\n\nCH Output: 21kW\n\nCH Output (BTU): 71,000\n\nErP Heating Rating: A Rated for Heating\n\nDimensions:\n\nHeight: 724mm\n\nWidth: 400mm\n\nDepth: 310mm\n\nWeight:\n\nGross Weight inc Packaging: 40kg\n\nWarranty:\n\n7 Years (Subject to manufacturer T\u0026amp;Cs)\n\n\u003ch3\u003eFAQs\u003c\/h3\u003e \u003ch4\u003eIs the 21kW output suitable for my home?\u003c\/h4\u003e The 21kW model is ideal for **medium to large properties**, particularly those with several radiators and a stored hot water cylinder. \u003ch4\u003eDo I need a hot water tank with this boiler?\u003c\/h4\u003e Yes — as a **system boiler**, it works with a hot water cylinder but does not require a loft-installed cold water tank. \u003ch4\u003eCan I add smart controls to this boiler?\u003c\/h4\u003e Absolutely. The Greenstar 4000 range supports a variety of **optional and smart heating controls**, including wireless and app-based options for better efficiency and convenience.\u003cbr\u003e\u003cp\u003eCheck out our full range of \u003ca href=\"https:\/\/jjbuildingmaterials.co.uk\/collections\/plumbing-supplies\"\u003eplumbing supplies\u003c\/a\u003e.\u003c\/p\u003e\u003cp\u003eBrowse more \u003ca href=\"https:\/\/jjbuildingmaterials.co.uk\/collections\/boilers\"\u003eboilers\u003c\/a\u003e available online.\u003c\/p\u003e","brand":"Worcester","offers":[{"title":"Default Title","offer_id":51955278086486,"sku":"146800","price":1375.68,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0905\/4509\/4998\/files\/worcester-greenstar-4000-21kw-system-boiler-7311354.jpg?v=1772638812","url":"https:\/\/jjbuildingmaterials.co.uk\/products\/worcester-greenstar-4000-21kw-system-boiler","provider":"JJ Building Materials","version":"1.0","type":"link"}