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Worcester Greenstar CDI Classic Combi Boiler [Review & Installation Prices]

Are you shopping around for a new Worcester Bosch boiler? The Greenstar 4000 is the popular new kid on the block, but its predecessors, like the Greenstar CDi Classic combi boiler range are still worth considering.

In our review of the Worcester CDi Classic, we’ll give you an overview of the models, talk about their features, warranties, and prices. Hopefully, by the end of this guide you’ll know if the Classic is worth it for you.

Greenstar CDi Classic Review
Want to get prices for the Greenstar CDi Classic? Use this price calculator and get a fixed quote on your screen in minutes.

Are the Greenstar CDi Classic Boilers Any Good?

Yes, the Worcester Bosch Greenstar CDi Classic combis are excellent.

The Worcester brand needs no introduction — it’s been awarded the Which? Best Buy for the ninth year in a row. And its Greenstar range includes some of the highest quality boilers out there. Like the CDi Classic — if you’re after energy-efficiency, user-friendliness, and proven reliability, then this is the boiler you’re looking for.

Greenstar CDi Classic Range: an Overview

The CDi Classic range from Worcester are combination boilers.

This means they heat hot water on demand, and don’t need a hot water storage tank or cylinder. If you have either of these water storage facilities, you’ll need a system boiler or regular boiler if you want to do a simple swap. However, you can still upgrade to a combi like the Classic and save yourself some space.

Although the Greenstar CDi boilers run on mains gas out of the box, you can easily convert them to operate on LPG instead (but not to oil). This may prove useful if you’re living off the gas grid.

You’ll get A-rating in efficiency with all Greenstar boilers, both for hot water and heating. And this efficiency could translate to some sizeable savings — perhaps enough to help you recover some of the cost of getting a new boiler.

In fact, if you’ve got a right ole’ banger of a boiler, a new Classic could save you up to £840 per year on energy bills, according to the Energy Saving Trust.

New boilers, fitted fast.
Buy your new boiler online at a fixed price, with next day installation included.

Note that CDi boilers ARE NOT compact, so you won’t fit them into a kitchen cupboard; instead, you’ll have to hang them on a wall.

If you prefer a compact boiler, consider the 28CDI Compact instead.

Or, you can opt for Worcester’s competition and check out the Baxi 600 or the Ideal Logic Plus — stellar appliances from reputable brands, which handily squeeze into a kitchen cupboard.

Looking for the cheapest place to get a CDi Classic installed?

We’d recommend checking out Heatable. They’re an online boiler installation company with a ridiculously tiny overhead and colossal deals from Worcester, so their prices are among the lowest in the industry.

What kind of fuel does your boiler use?

Fixed price online with next day installation

Worcester boilers from as little as £1,965.

What Size Greenstar CDi Classic Do You Need?

The Classic range gives you a choice between the following boiler sizes:

  1. Greenstar 29CDi Classic
  2. Greenstar 34CDi Classic
  3. Greenstar 38CDi Classic
  4. Greenstar 42CDi Classic

Unsure about what size CDi Classic combi boiler you need for your property? No problem — this quick table below gives a rough idea of which boiler size you need:

Boiler Property Type
29CDi Medium in size, approximately 12 radiators, and only one shower/bath in use at once
34CDi Slightly higher output, but suitable for a similarly sized property as above
38CDi Medium-large property with approximately 14 radiators, and 2 showers in use at once
42CDi Medium-large property with approximately 14 radiators, and 2 showers in use at once

Whilst this table gives you an overview of how boiler sizes typically work, sizing a boiler correctly involves a few more variables. That’s why we suggest you jump over to this boiler size calculator and get a professional recommendation on the size of your new appliance. You’ll see the most suitable boilers for your property — along with fixed installation prices — at the top of the page.

Worcester Greenstar CDi Classic Review

Power Output & Size

Don’t let the names fool you. Whilst most boiler names indicate their kW output, all 4 models in the Classic combi range have a central heating output of 30kW. It’s the hot water output that gives this range its designations:

  • Greenstar 29CDi Classic: 30.9kW
  • Greenstar 34CDi Classic: 35kW
  • Greenstar 38CDi Classic: 40kW
  • Greenstar 42CDi Classic: 42kW

Now, 30kW is reasonable for central heating, and enough to power anything up to a typical 4-bedroom property. For such a powerful boiler, the Greenstar CDi Classic is reasonably compact too. Dimensions for the 29CDi, 34CDi, 38CDi, and the biggest boiler in the range, the 42CDI, are 760 x 440 x 360. Again, it won’t fit in your kitchen cupboard; but it won’t take up half your wall, either.

Greenstar CDi Flow Rate

The Greenstar CDi Classic range differs slightly in flow rate, too.

The higher the flow rate, the more taps and showers you’ll be able to power at once — an essential factor for combis, which don’t come with hot water cylinders.  Here’s the flow rate you can expect from each model in the range:

Boiler Flow Rate
29CDi 12.3 litres per minute
34CDi 14.3 litres per minute
38CDi 16.4 litres per minute
42CDi 17.2 litres per minute

As you can see, if you live in a small home with 1 shower, you can go for the 29 or the 34 Classic. For most medium-sized properties, you’ll need the Greenstar 38CDi Classic. And for large properties, you’ll be heading for the 42CDi Classic.

Greenstar CDi Classic Anti-Freeze Features

The Classic range incorporates a crucial feature — an improved condensate syphon. According to Worcester, this device stops your boiler from freezing up and locking out down to temperatures of -15°C, for up to 48 hours (source). And that’s great news.

Back in March 2018, we had a cold spell. Typical temperatures throughout the UK were around -4°C for multiple days. Naturally, in the likes of Scotland and Wales, the temperatures were even lower.

We had an influx of 10x the amount of people visiting our website, looking for ways to fix their boiler. The problem 99% of people faced? A frozen condensate pipe. That’s always the first place to start when fixing a boiler in these temperatures.

Whilst it’s not a major issue and can be fixed easily. It’s still down time for your boiler, as well as an emergency boiler repair call out fee. Not good!

With the Greenstar CDi frost protection feature, you needn’t worry about your boiler giving up due to frost risk just when you need it most — in the midst of a cold spell. This feature also means that the Classic can easily be installed in a garage or loft.

Greenstar CDi Classic Warranty

As I’ve mentioned in many of my boiler reviews, warranty is something that buyers should always consider. With their warranty, a boiler manufacturer is essentially telling you what they think of their own boiler.

See a 2-year warranty? They think their appliance is garbage.

Found a 5-year warranty? Now we’re talking — we’d never buy a boiler with less than 5 years.

The Worcester Greenstar CDi Classic range has one of the highest warranties of any boiler — you’ll be able to grab up to 10 years.

Typically, to get this long warranty, you’ll need to use a Worcester Accredited installer. These aren’t employed by Worcester, but are simply Gas Safe engineers that have completed Worcester’s training program.

Alongside a suitable installer, you’ll likely need to get a magnetic system filter installed, as well as Worcester-branded boiler controls.

Worcester’s warranty conditions can be confusing, and change all the time; so, make sure you read the small print before getting your boiler installed.

Heatable is an accredited installer which always gets you a 10-year warranty on Worcester Bosch boilers, including the Greenstar CDi Classic. They also fit a magnetic system filter as part of the deal. You can find out how much the entire package will cost by filling out Heatable’s anonymous, 90-second questionnaire.


Prices for the Greenstar CDi Classic vary a great deal. If you’re looking to buy a boiler direct, here are some prices you can expect to pay:

Boiler Price (inc VAT)
29CDi £1,100
34CDi £1,200
38CDi £1,400
42CDi £1,600

Don’t scrimp by buying a smaller model than you should.

To ensure you get the right size boiler, we’d suggest using this boiler size calculator. Alongside the most suitable sized boilers at the top of the screen, you’ll also get a fixed price for your installation.

Installation Prices

The prices mentioned above are for the boiler only. On top of this, you’ll need materials (such as a flue, filter and copper pipe), and, of course, the labour.

So, how much is it going to cost to install a Greenstar CDi Classic on your property? The prices below include the entire package, boiler plus installation:

Boiler Installation Price
29CDi £2,100
34CDi £2,200
38CDi £2,400
42CDi £2,600

As you can see, a typical labour-only price is around £1,000. This includes all parts associated with the install (filters, pipe, fittings), as well as fitting by a Gas Safe registered installer.

Prices will vary. For quotes without boiler filters, for a true straight swap, the labour cost could be as low as £600 (again, including the flue, etc). But overall, expect to see an average of around £1,000 across multiple quotes.

You can get fixed prices for a Classic boiler, including installation, here.

Where to Get Installation Quotes for Your Greenstar CDi Classic

We’ve created an incredibly detailed guide to getting a new boiler fitted. It covers everything you need to know and offers a detailed comparison of installation prices from British Gas, Help-Link, Heatable, and even local installers.

Can’t be bothered to read the full guide? Here’s short version:

  1. Get multiple quotes from local installers, and then compare them back-to-back.
  2. Then, jump onto Heatable (an online boiler installation company that we highly recommend) and compare all the quotes you’ve got.
Heatable boiler installations

Protecting Your CDi Classic Combi Boiler

Make sure your installation quotes are itemised. One thing we’d recommend is fitting a boiler filter (there’s a quick guide to boiler filters here).

These filters help to catch debris in your heating system. And whatever these filters catch isn’t getting lodged in your boiler and causing problems. That’s a good thing, by the way.

Worcester actually make their own system filter, in both 22mm and 28mm, depending on the size of the return pipework to your boiler.

So, when you’re comparing quotes back to back, check to see which installers offer a system filter to protect your boiler.

What’s Next?

Thanks for reading our review of the Worcester Greenstar CDI Classic range.

We regularly post up boiler reviews, money saving tips, and boiler fault finding guides. Like what you’ve read? Bookmark this page and pop back soon.

Have an opinion on a Worcester boiler, or a question about another brand?

Leave a comment below, and we’ll get back to you as soon as we can.

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