Worcester Bosch Greenstar 25i Combi Boiler REVIEW (2021)

The Worcester 25i has not always been the flagship range. Up until 2015, Worcester manufactured their “Junior” range. This included the 24I Junior which has now been replaced with the 25i.

In this review of the Worcester 25i combi boiler we will walk through:

  • Improvements to the Greenstar range
  • The best alternatives
  • Differences in prices
  • Our review verdict

Worcester Bosch Greenstar 25i Combi Boiler REVIEW

Worcester 25i Prices (Boiler Price + Installation Cost)

So, the question is, how much does the Worcester 25i combi boiler cost? Typically with Worcester Bosch, you’re going to find their prices are up there with the more premium boiler brands on the market. You’ll be comparing them directly with the likes of Baxi and Vaillant.

From plumbing merchants, expect to see prices for the Worcester 25i, in the £950 region. That’s going to be a “boiler only” package. So, if you need a new flue, extensions and a timer, that’s all going to come at an additional cost.

So, how much is the Worcester 25i going to cost to install? With a £950 sale price, you should expect to pay somewhere in the region of £2,100 for an installation from a local engineer. Of course, the exact price depends on the materials they need, and the complexity of the install.

We’ve recently come across a cheaper way to get Worcester boilers installed, including the 25i, and that’s with HEATABLE.

It goes without saying that HEATABLE are probably getting the 25i cheaper than any other installer in the country, for this very reason. And, that means you’re going to be able to save money when it comes to cost of the installation.

HEATABLE have an online fixed price quotation system, which is pretty-cool. It takes around 90 seconds (seriously, I just did it). Here’s the quote I got for a new Worcester 25i including installation.

Worcester Bosch Greenstar i from Heatable

You can see from my quote, I got a price of £1,770 including VAT. And I’m not joking, that’s really-cheap. But, it doesn’t stop there. Included in the price, I’ve got 3 extras as well:

  1. A free Honey Well thermostat, RRP is £199.99
  2. An initial clean of my heating system, which is going to protect my boiler
  3. A long-term preventative measure, to stop my boiler getting blocked up with heating sludge, a heating filter. These are worth around £130.

But don’t take my word for it. You can get itemised quotes from up to 3 local boiler installers here.

Then, you can get a fixed online quote from HEATABLE, here.

Compare the two, to get the best price on your Worcester 25i.

What size combi do you need?

Before going any further, it’s important to understand whether this is the correct sized boiler for your property. The 25i is suitable for properties up to 3 bedrooms, if they have low demand for hot water and heating. Not sure if it’s right for you? Use this boiler size calculator and the most suitable sized boilers will be displayed at the top of the screen.

The most suitable properties are likely to have no more than 1 shower, and only 2 bedrooms. This includes small apartments, flats and 2-bedroom terraced houses.

If you have a property with 2 or more showers, more than 10 radiators, or more than 3 bedrooms, it’s likely you are going to need something much bigger.

If you are looking for a boiler that’s the next step up from the 25i, checkout our review of the Worcester 30I here. And, if that’s not enough, we usually recommend checking out the Vogue C40 from Ideal Boilers.


Many installers will mention that the Worcester range is not just more difficult to install than other brands, but also to service. As a property owner, that means that installation and servicing costs increase.

This is something that Worcester have worked on for both the 25i and 30I, and the main components are much easier to access.

Alongside this, the control panel offers a lot more details when it comes to boiler faults, meaning an engineer can usually diagnose problems over the phone (saving you expensive call out fees).

Frozen Condensate Pipes & Pumps

One of the main reasons we are called out to fix boilers, relates to frozen condensate pumps and pipes. When residue freezes, and blocks these components, the boiler will lock out and stop working.

The Worcester 25i now incorporates a CondenseSure Siphon. This acts as a preventative measure for condensate freezes.

This not only means you’ll have fewer problems in the winter months, but you’ll also be saving money on expensive engineer call out charges.

Boiler Display Panel

A big gripe for owners of the 24I Junior was the lack of functionality (and complexity) of the display panel. It was ugly, hard to use, and didn’t help users fix the simplest of problems.

Fortunately, the Worcester 25i now has increased functionality. Users can now adjust the hot water and heating temperature on the panel without the use of a thermostat.

And that isn’t all, when there is a problem with the boiler, it will display the relevant fault code which makes a fault much easier to diagnose and fix for an engineer.

Increased Hot Water Output

Worcester are always trying to increase the hot water output on all their boilers. So, the Worcester 25i combi now has 25KW of output, up from its original 24KW.

Exceptional Warranty

Like all the Worcester range, the 25i comes with a basic 5-year warranty. This can be increased by 1 year, by adding a magnetic system filter. It’s important to note that the filter must be a Worcester Bosch branded filter to get this extra warranty.

HEATABLE are one of the biggest installation companies fitting Worcester boilers. You can get a fixed price on screen for a Worcester 25i with a 10-year warranty here.

Boiler Controls

One of the most popular new controls that can be used in conjunction with the 25i is the Worcester Wave. It’s a smart, Wi-Fi powered, heating control. It means you can set and change your heating using their Wave app.

This can cost upwards of £180, so ask an engineer for suitable alternatives if you don’t require Wi-Fi based stats and timers.

Worcester 25i V Worcester 25SI Compact

The Worcester Greenstar range doesn’t just consist of the I, but also the SI Compact range. Both boilers are combination boilers. So, how does the 25SI Compact differ?

The 25SI Compact is Designed for Small Installation Areas

The main reason people buy the 25SI Compact over the I, is size. For instance, if you were fitting a boiler in a kitchen cupboard, or under your stairs, it’s unlikely that the 25i will fit. The 25SI Compact has been designed with these small spaces in mind.

And, This Comes at a Cost

Although the prices of boilers change all the time, we find there is a constant in price differences. If you need a 25SI Compact, expect to pay around £95-105 more than the standard Worcester 25i.

Which is The Best Worcester Boiler?

If you don’t need to install a boiler in a tight space, the 25i would be the obvious choice. The 30SI Compact really has little benefit in comparison, and costs more.

Obviously, if you need to fit the boiler in a tight space, you’ll be leaning towards the Compact.

Alternatives to The Worcester 25i

There are a tonne of alternatives to the Worcester 25i.

First, let’s start with Ideal Boilers.

These are becoming more and more popular. You can see an overview of the Ideal Logic Plus and the Ideal Vogue here. You’ll be looking at the Ideal Logic Plus 24, and the Ideal Vogue 26.

So, why do we recommend these boilers?

  1. Quality
  2. Warranty
  3. Price

We rarely get any comeback after installing Ideal Boilers. On the flip side, the Ideal Logic Plus (7-year warranty) tends to be around 10% cheaper than any Worcester, and the Vogue (10-year warranty) around the same price.

Other Worcester 25i alternatives worth researching are:

  • Baxi Duo-Tec 24
  • Vaillant Eco-Tec Pro 24 and the Vaillant Eco-Fit Pure 825
  • Vokera Excel 24 (budget option and considered much lower quality)
  • Potterton Gold 24

The Review Verdict

Space is the first thing to consider. If you are restricted by space, and are 100% convinced you want a Worcester, the Worcester 25SI Compact is going to be your only option. If space is not an issue, then you’ll be looking at the Worcester 25i.

If you are more bothered about price and warranty, the Ideal Boiler range is an obvious choice. But, not so much so now you can get the 25i from HEATABLE at a similar price.

The Ideal Logic Plus 24 will save you around 10%, and you’ll get a 7-year warranty. If you’d prefer a higher warranty, the Ideal Vogue C26 will give you an extra 3 years.

Avoid Expensive Breakdown Costs
Boiler Replacement Promise: If it's under 7 years old and we can’t repair it, we’ll replace it.
Try YourRepair. From £9/mo
All plans include: annual boiler service, all parts and labour, unlimited support and 24hr helpline.

    Leave a comment

    Your email address will not be published. Required fields are marked *


    Fix things and tutorials

    Get a Boiler on Finance

    The best pay monthly packages available

    Read guide
    Heatable Boiler Replacement

    Want a new boiler from HEATABLE?

    Read guide
    WarmZilla Boiler Replacement

    Want a new boiler from WARMZILLA?

    Read guide
    Boiler Installation Costs

    Confused about new boilers and their costs?

    Read guide