Assess First. Recommend Second.
The cylinder-based 4000 choice, with five heating options and a separate stored-hot-water design to assess.
Model names identify discrete variants. The heating and hot-water columns reproduce the stated output basis from the cited manufacturer documentation; they are not interchangeable. Where a model label differs from rated output, compare the rating rather than rounding it to the name. An oil model band describes that appliance’s settings, not every integer as a separate model to buy.
| Exact model / fuel variant | Fuel | Heating output (kW) | DHW output (kW) |
|---|---|---|---|
| Greenstar 4000 12kW System NG · Part 7 733 600 377 | Gas (NG) | 12 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 12kW System LPG · Part 7 733 600 378 | Gas (LPG) | 12 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 15kW System NG · Part 7 733 600 379 | Gas (NG) | 15 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 15kW System LPG · Part 7 733 600 380 | Gas (LPG) | 15 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 18kW System NG · Part 7 733 600 381 | Gas (NG) | 18 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 18kW System LPG · Part 7 733 600 382 | Gas (LPG) | 18 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 21kW System NG · Part 7 733 600 383 | Gas (NG) | 21 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 21kW System LPG · Part 7 733 600 384 | Gas (LPG) | 21 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 24kW System NG · Part 7 733 600 385 | Gas (NG) | 24 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
| Greenstar 4000 24kW System LPG · Part 7 733 600 386 | Gas (LPG) | 24 Maximum heating output in the current product guide | Not a combi DHW rating; cylinder design is separate |
The current gas/oil product guide documents all five LPG variants as well as the natural-gas versions shown on the product page.
Unless an operating temperature is expressly stated, the current product-page output label does not specify its measurement temperature. The exact installation literature must be checked before technical design; no modulation range or seasonal performance claim is inferred here.
A system arrangement brings the boiler and cylinder into one coordinated design. Front service access helps maintenance planning; cylinder recovery, valves and control compatibility still need checking.
The cylinder-based 4000 choice, with five heating options and a separate stored-hot-water design to assess.
A separate hot-water cylinder is required for the stored-hot-water arrangement described here. Assess the cylinder capacity, recovery, condition and safety requirements alongside the boiler. A system arrangement may suit a household retaining stored hot water, but the boiler and cylinder must be designed together. Check the expansion arrangements, controls and pump provision for the exact appliance; specialist Condens designs require separate hydraulic planning.
For a gas installation, assess the available gas supply, flue route, condensate disposal, controls, electrical connections and service clearances. Natural gas and LPG are distinct fuel configurations: a listed LPG variant does not authorise using the natural-gas appliance unchanged. Confirm the exact part number and any commissioning requirements in the installation instructions. SwiftHeat checks installer competence and the required installation scope before accepting the work.
A like-for-like arrangement and a conversion have different scopes. Check pipework condition, system cleaning and protection, controls, siting and future access before comparing quotations. Removing a cylinder, relocating the boiler or changing fuel can affect the whole project. Bedroom count, bathroom count and the model designation cannot replace a heat-loss calculation and a water-supply assessment.
Manufacturer standard cover: 7 years. With the qualifying system filter: 8 years. Maximum eligible extended cover: 10 years, conditional on a Greenstar System Filter and the qualifying installer loyalty/accreditation arrangement in the manufacturer terms. A System Filter Micro does not qualify for this longer extension. SwiftHeat’s installer status and your package must be confirmed in writing; the maximum is not automatically included.
The manufacturer guarantee and SwiftHeat service offers are separate. Your written quotation must identify the exact cover and eligible accessories. Keep installation and commissioning records, complete manufacturer registration in the required time and arrange the annual servicing required by the applicable terms. The installer must establish eligibility before promising extended cover.
Current guarantee schedule · Manufacturer guarantee terms · Arrange ongoing servicingVerified 1 October 2026. Product availability and manufacturer terms can change; the final specification is checked again at quotation.
Exact manufacturer product information · Verified technical source 1 · Official manuals and technical literatureThe installed price for your selected boiler is confirmed after assessment. The quotation covers the appliance, controls, flue, system preparation and any required pipework. A conversion or relocation can have a different scope from a straightforward replacement.
New boiler installations from £1,790 inc. VAT apply to a qualifying standard, straightforward replacement: one bathroom, fewer than 10 radiators and a standard horizontal flue, subject to survey. Specification and warranty selection affect the final cost. This is a general starting offer and is not a price for every model in this catalogue.
Read the starting-package conditions0% options over 3, 6, 9 or 12 months through Humm Group Limited, subject to application, affordability, eligibility, approval and provider terms. Any applicable deposit, fees and repayment conditions are confirmed during your enquiry/application. Acceptance is not guaranteed.
Finance terms and chargesTwo free annual services and a Hive Mini are available on qualifying installations only. Every model is considered under the qualification rules; inclusion in this catalogue does not confirm eligibility. Ask us to confirm the offer in your quotation.
Ask about Care+ eligibilityPlan the maintenance your appliance requires and keep its service records. If you are considering replacement because of a fault, diagnosis can help establish whether repair is a suitable option first.
Boiler servicing · Repair advicePrice confirmed following assessment for this configuration. The general New boiler installations from £1,790 inc. VAT offer does not apply to every model or property.
From or indicative prices remain provisional. SwiftHeat issues a written fixed quotation for the agreed scope after the appropriate property and installation assessment, technical checks and warranty-package verification. Remote information gathering may be suitable initially; a home survey is required where the necessary checks cannot be completed remotely.
We assess heat loss, heating and hot-water requirements, water supply, controls and installation access before recommending an appliance. Bedroom count or a catalogue model number alone cannot establish the right boiler.
Gas Safe registration 978273 · Serving Cardiff, South Wales and across the UK.
Understand suitable boiler types · Start the Boiler Finder · Our installation assessment · Areas we cover
