WORCESTER BOSCH GREENSTAR 18i
The Worcester Bosch Greenstar 18i Classic System was a popular wall-mounted system boiler from the Greenstar i range and remains installed in many smaller homes today. While it is no longer manufactured, this page explains its specification, who it was designed for and your options for servicing, repairs or replacement.
We continue to service and repair this model regularly across Buckinghamshire, Berkshire, West London and surrounding counties.
Need help with your Greenstar 18i? Contact our Worcester Bosch accredited and Gas Safe engineers.
What is the Greenstar 18i Classic System?
The Greenstar 18i Classic System is a wall-mounted gas system boiler from Worcester Bosch’s Greenstar i range. Designed for smaller homes with an existing hot water cylinder, it was a reliable and efficient choice for properties upgrading from an older regular boiler to a more modern system boiler.
Unlike a combi boiler, a system boiler works alongside a separate hot water cylinder to store and deliver hot water. This means it can supply multiple taps and outlets simultaneously, making it better suited than a combi for homes with higher hot water demand.
The Greenstar 18i Classic System was part of the widely respected Greenstar i range, which consistently won the Which? Best Buy award and became Worcester Bosch’s most popular wall-mounted system boiler series.
> Explore the full Worcester Bosch Greenstar range
Greenstar 18i Classic System: Key Specifications
✔ Boiler type: System boiler
✔ Central heating output: 18kW
✔ Efficiency rating: A rated / 94%
✔ Fuel type: Natural gas or LPG
✔ Dimensions: 710mm x 400mm x 330mm
✔ Frost protection: Yes
✔ Solar compatible: Yes, compatible with Greenskies panels
✔ Smart control compatible: Yes, including Bosch EasyControl
✔ Suitable for: Smaller homes, up to 15 radiators, 1 bathroom with cylinder
Who is this boiler suitable for?
The 18i Classic System was designed for smaller properties with an existing or new hot water cylinder and modest heating demand. It is best suited to properties with:
- 1 to 2 bedrooms
- 1 bathroom
- Up to 15 radiators
- An existing hot water cylinder
- No loft cold water tank required
For homes with greater heating demand, the 21i, 24i or 27i Classic System offered higher outputs within the same range. If you already have an 18i Classic System installed and are unsure whether to service, repair or replace it, our engineers can assess your system and give you honest advice.
Servicing and repairing your Greenstar 18i Classic System
Although the 18i Classic System is no longer manufactured, it can still be serviced and repaired. Parts remain widely available for this model and our Gas Safe engineers carry out full services and fault diagnosis across Buckinghamshire, Berkshire, West London and surrounding counties.
Regular servicing is important for any boiler, but particularly for older models. An annual service helps to:
- Maintain efficiency and keep running costs down
- Identify worn components before they cause a breakdown
- Keep your boiler operating safely
- Satisfy any remaining warranty or insurance requirements
If your 18i Classic System has developed a fault, our engineers carry a wide range of Worcester Bosch parts and aim to resolve most repairs in a single visit.
When to consider replacing your 18i Classic System
If your boiler is over 12 to 15 years old or experiencing repeated breakdowns, replacement is often the more cost-effective long-term decision. The Greenstar 18i Classic System has been replaced by the Worcester Bosch Greenstar 4000 System, which offers meaningful improvements across efficiency, warranty and controls.
The Greenstar 4000 System is the natural modern equivalent for smaller homes currently running an 18i Classic System. It delivers better efficiency, a longer warranty and full compatibility with the Bosch EasyControl smart thermostat.
Greenstar 18i Classic System vs Greenstar 4000 System
Efficiency: 94% vs up to 94%
Warranty: 5 to 7 years vs up to 10 years
Controls: Basic display vs smart control ready
ErP rating: A rated vs A rated
Status: Discontinued vs current model
> Learn more about the Greenstar 4000
Why choose Heppelthwaite – Red Van Plumbers?
Fewer than 5% of UK installers achieve Worcester Bosch Platinum Accredited status. As Platinum Accredited Installers, we install, service and repair the full Greenstar range, including legacy i range system boilers, across Buckinghamshire, Berkshire, West London and surrounding counties.
- Platinum Accredited Worcester Bosch Installers
- Family-run business established 1948
- Gas Safe registered engineers
- Free fixed quotations with no hidden costs
- Up to 10-year warranty available on new Greenstar 4000 installations
> Request a free quote or call 01628 533 550
FAQs – Worcester Bosch Greenstar 18i Classic System
Is the Worcester Bosch Greenstar 18i Classic System still available to buy?
No. The 18i Classic System is no longer manufactured. The modern equivalent is the Worcester Bosch Greenstar 4000 System boiler, which offers an improved warranty and smart control compatibility.
Can the Greenstar 18i Classic System still be serviced?
Yes. Parts remain widely available and our Gas Safe engineers service and repair all Greenstar i system models across Buckinghamshire, Berkshire and West London. Annual servicing is recommended to maintain efficiency and safety.
What replaced the Greenstar 18i Classic System?
The Greenstar 18i Classic System was replaced by the Worcester Bosch Greenstar 4000 system boiler range. The 4000 offers smart control compatibility and up to a 10-year warranty when installed by a Platinum Accredited Installer.
What is the difference between a system boiler and a combi boiler?
A system boiler works alongside a separate hot water cylinder, storing hot water for use on demand. This means it can supply multiple taps and bathrooms simultaneously. A combi boiler heats water instantly from the mains without a cylinder, making it more compact but less suited to higher hot water demand.
What size home is the Greenstar 18i Classic System suitable for?
The 18i Classic System is suited to smaller homes with 1 to 2 bedrooms, 1 bathroom and up to 15 radiators. For homes with greater heating demand, the 21i or 24i Classic System offered higher outputs within the same range.
How long should a Greenstar 18i Classic System last?
With regular annual servicing, a well-maintained 18i Classic System can last between 12 and 15 years. If your boiler is approaching or has exceeded this age, it may be worth considering a boiler replacement to avoid repeated repair costs.
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