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Worcester Bosch Greenstar 18Ri Regular Gas Boiler


Worcester Bosch is perhaps the leading manufacturer in the boiler industry, and this boiler is evidence of their workmanship. The Greenstar 18Ri Regular Boiler is the definition of modern. Not only does it come with almost all of the latest features for more comfort, but it’s also built to save you money in the long run.

It’s ideal for homes with around 2 bathrooms and 3 bedrooms. Despite its seemingly low output rating, you have to consider that it’s a regular boiler. If it were a combi boiler, 18kWs wouldn’t be enough.

Worcester Bosch Greenstar 18Ri Key Features

  • It’s a modern condensing boiler.
  • It has a 92% efficiency rating.
  • It’s ErP A-rated for both central heating and hot water production.
  • An aluminium-silicon heat exchanger.
  • It has easy-to-use controls
  • A sound pressure level of 50 dB
  • Hot water max output of 18kW
  • Central heating max output of 18kW
  • A central heating range of 30 to 87 ℃
  • 61,419 BTU
  • It can serve up to 10 radiators.
  • It comes with a standard 5-year warranty extendable to 10 years.
  • It has a frost-protected thermostat.
  • It’s compatible with smart thermostats and timers
  • Compatible with Greenskies solar panels.
  • It’s compatible with a wide range of flue options.
  • Compact dimensions of 600mm Height by 390mm Width by 270mm Depth.


The Greenstar 18Ri Regular Gas Boiler has a simple but solid build. Unlike other boilers, its user interface is simple. It has two temperature control knobs and the famous Worcester Bosch neon status indicator.

On the inside, it boasts a quality aluminium-silicon heat exchanger that will survive the test of time and service. Speaking of survival, it also has a condensate siphon resistant to freezing during the harsh winters. Your condensate pipe will not freeze even in conditions of -15℃. However, to get the most of the feature, we advise you to use 32mm pipework that doesn’t exceed 3m in length.

Finally, we’d also like to appreciate the 18Ri’s compact dimensions. It will easily fit in most standard kitchen cabinets.

Fuel and efficiency

Although it mainly runs on natural gas, the Greenstar 18Ri Regular Boiler is also compatible with LPG (You’ll have to use a converter). That said, you’ll never have to worry about high heating costs thanks to its 92% efficiency rating. On top of that, it’s also ErP A-rated for both central heating and domestic hot water production.

If you want to save even more money, you can bank on its compatibility with Worcester Greenskies solar panels.

Finally, it can also run on a 20% hydrogen blend.

Power output rating

The Greenstar 18Ri Regular Boiler is the 3rd best in the Ri product range. With a hot water and central heating output of 18kW, it will serve most medium-sized households with, at most, 2 bathrooms and 3 bedrooms. Indeed, it’s more capable than a combi boiler offering the same output rating. Nonetheless, it’s a regular boiler that will occupy more space because of its hot water cylinder and cold water tank.

If your household is smaller, you should consider the 9kWs, 12kWs, and 15kWs variants. Likewise, if your house is bigger with more demand for heat, consider the more powerful 21kWs and 24kWs variants.

Installation and servicing

Worcester Bosch boilers are among the easiest to install. The Greenstar 18Ri Regular only weighs around 22.6kgs and shouldn’t require more than two engineers to install. Also, its flue is multi-directional for more flexibility.

Finally, it has a frost protection thermostat. You can install the 18Ri in the most unconventional places like lofts and garages. That way, it will not cramp your home’s decor.

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