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The Best Cheap Combi Boiler [And Typical Combi Boiler Prices for 2021]

Welcome our review of the 28CDi Compact from Worcester Bosch. If you’re looking for a boiler to suit a mid-range property, the CDI Compact from the Greenstar range is one that’s most likely made your short list.

In this review, we’ll cover not just details relating to the 28CDI Compact, but how it compares to other boilers in the Worcester range, and other brands in terms of price.

For those in a hurry go get an exact quote in 90 seconds by filling this online form from Heatable — which we think offer the best service by installing Worcester Bosch boilers for fixed prices starting at £1,785.

Worcester CDI Compact Boiler Review

The most popular boiler in Worcester’s CDI Compact range is the 28CDI. However, there are two others in that range (explained below), being the 32CDI Compact and the 36CDI Compact.

Suitable Property Size

The Worcester Greenstar 28CDI Compact is a relatively small boiler. Being called the 28CDI might indicate that output is 28kw, which would power up to a 3-bedroomed home, but it’s not.

The 28 CDI only provides 24kw of heating output. And typically, you’d be looking at small properties here. That’s 1-2 bedroomed flats, apartments, and houses. Realistically, you’re going to struggle to warm up more than 10 radiators.

Output For The 32CDI & 36CDI

There are two other CDI Compacts in the range. The 32CDI and the 36CDI. Again, the names are a bit misleading. These ALSO have 24kw of heating output.

It’s the flow rate that differs here. The 28CDI is 10L, the 32CDI gets 11.5L and the 36CDI gets 12.9L.


The best way to compare the price of the Worcester 28CDI Compact versus other boilers in the range, is to head over to Heatable. There’s a clickable multiple choice form that takes around 90-seconds to complete and requires no personal details. You’ll get a fixed price (on-screen), for all boilers that are suitable for your property, including the 28CDI.

As Heatable are a new company (for online boiler installs) focusing on technology rather than salespeople, the prices here are about as good as you’ll get, with no hidden extras.

We just plugged in details that lead to a 28CDI Compact landing on screen. It’s £2,120, including:

  • System flush and clean
  • Magnetic system filter, worth up to £130, but that’s just the price of the filter, you’d expect them to cost around £200 including installation
  • £199.99 Honeywell Smart Thermostat
  • Long 10-year warranty

The price may vary depending on your exact property requirements, but you can get your price from Heatable here.


All Worcester CDI Compact boilers fit in a kitchen cupboard. The display is easy to use, allowing you to adjust hot water and heating from the control panel.

You’ll get in-built frost protection, which is particularly important when temperatures start dropping below zero. That’s going to stop your boiler locking out, and remove the need for you to call in a boiler repair engineer. It’s even more important for those looking to install their boiler in a loft or garage, where it’s going to be more exposed to the elements.

And, thanks to the low energy pump, electrical consumption is minimal. Combined, that makes this a boiler that’s up to 92% efficient, giving it an A+ ErP rating.

What kind of fuel does your boiler use?

Grab your fixed price online by 3PM, and get next-day boiler installation.

Worcester boilers installed from as little as £1,795.


Worcester Bosch boiler warranties are ridiculously confusing. They change constantly, vary depending on which additional Worcester branded products are installed alongside the boiler (such as a filter), and whether or not they are installed by a Worcester Accredited engineer.

At time of writing, the CDI Compact range comes with a 7-year standard warranty. This can be extended to 9-years if you use an Accredited Installer.

Essentially, these installers AREN’T Worcester engineers, they are the same as any other Gas Safe engineer, but they’ve been on a training course provided by Worcester. Lots of local installers will have been on this course.

The Best Alternatives

You’ve got a whole host of alternatives to the CDI Compact range. Although Worcester Bosch and their Greenstar are the most popular, as well as the most well known, there are plenty of alternatives that stack up nicely in terms of quality, and much better in terms of price.

Do You Need A Compact Boiler?

First of all, do you actually need a compact boiler? In general, you’ll pay 10-20% more for a compact, over a normal boiler.

The main idea behind compact boilers, is to fit into your average kitchen cupboard. So, if you’ve already got a boiler installed in a kitchen cupboard, or have a wall-hung boiler and would prefer it tucked away in a kitchen unit, you’ll need a compact.

However, if you’re planning to replace a wall-hung unit, or simply fitting a boiler in an airing cupboard, you don’t necessarily need a compact, so we’ll give you an alternative below.

Worcester 25I

If you’ve decided you’re dead-set on a Worcester Greenstar, but you don’t need it to fit in a kitchen cupboard, you’ll want to head for the 25I, or 30I.

You’ll get similar flow rate and heating output (actually, 1kw more, at 25kw) from the Worcester 25I. The big difference when compared with the CDI Compact? It’s about £200 cheaper.

We’ve written a full review here.

Baxi 600 Compact

If you’re looking for a Compact boiler, but don’t want to burn cash for the sake of it, I’d suggest checking out the Baxi 600. Like the CDI Compact, the Baxi 600 will fit into a standard kitchen unit, so can be installed out of sight.

They offer a 24kw and 30kw version, so there’s an option for those in small to medium sized properties.

Baxi are nowhere near as well known as Worcester Bosch, but their products are top notch. They just don’t have the budget to market themselves like Worcester do. And, they’ve recently launched the Baxi 600.

The best thing about the Baxi 600? It’s ridiculously cheap. In fact, you’ll be looking at paying £800-900, rather than £1,100 for the CDI Compact range.

Other features include smart technology capability and it’s hugely lightweight (so, easier and cheaper to install).

We’ve written a full review of the Baxi 600 here, so you can compare it directly to the 28CDI.

Getting Your Compact Boiler Installed

If you’re not 100% sure about which boiler is the most suitable, speak to an engineer. As part of a quote, they’ll spec your property, ensuring the boiler you’re about to buy has the output to supply hot water and heating at sufficient levels.

A boiler installation can cost more than £2,000. So, the last thing you want, is to have the wrong boiler fitted; it’s likely you’ll have to live with it for 10+ years!

You can get your fixed price from Heatable in less than 90 seconds here.

What’s Next?

Thanks for reading our review of the Worcester CDI range. Hopefully, that gives you an idea of what you’re getting for your money, and the alternatives that are out there.

Still got questions about the Worcester CDI Compact range? Drop a question below and we’ll get back to you as soon as possible.

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