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What’s The Best Combi Boiler For a 4 Bedroom House?

You’re probably overwhelmed by kW outputs, brands, and quotes with huge, unexplained price differences. We’re here to tell you what’s the best combi boiler for your 4 bedroom house?

In this guide, we’ll walk you through specific combi boiler models that work well for a house with 4 bedrooms. We’ll explain these combi boilers’ warranty terms, installation costs, and tell you how much you should expect to save on energy bills.

Combi boiler for 4 bed house

Note that this guide relates to combination boilers only. If you’re looking for a heat-only or a system boiler, you’ll want to use this boiler calculator (multiple choice form with toggle navigation) to determine which is best boiler for your property; kW output will vary depending on what kind of boiler your central heating system has.

What Size Combi Boiler For a 4 Bed House?

The problem with boiler sizing is it’s not a one-size-fits-all approach.

For instance, your 4 bedroom house might only have one shower and 9 radiators. Another 4 bedroom home might have 15 radiators, a much longer heating run, and 2 showers.

All of these factors affect play a role in deciding what size boiler you’re going to need. And that’s why most Gas Safe installers want to come out and spec your property to ensure the boiler is the correct size, rather than billing you to install a boiler that’s too small or too large.

Here’s what happens if you get the boiler size wrong:

  • Combi Boiler Too Small

You’ll struggle to heat your home or use taps and showers at the same time.

  • Combi Boiler Too Big

Well, that’s just burning cash for the sake of it, both in purchase costs and heating bills.

Boiler Size Calculator

We used this quick boiler calculator from Heatable. In about 60 seconds, we got our suggestions, with the Worcester Bosch Greenstar 4000 30kW being the best boiler for a 4-bed house. Keep in mind, given the market’s current volatile state, you might get a different price quote than us.

Worcester Bosch Greenstar 4000

A Note on Compact Combi Boilers

If you’re looking to fit your new boiler in the existing location, and its wall-hung, in a garage, or large installation area like an airing cupboard, you won’t need a compact boiler.

However, if you’re fitting it in a small space like a kitchen cupboard, you’ll need a compact boiler.

Usually, a compact boiler will be around £100-150 more expensive than the equivalent, non-compact version. You can compare prices between compact/non-compact on screen here.


Now that you know what size boiler you need, the next thing to take note of is warranty. Combi boiler prices vary considerably, and whilst some of the price gaps are due to the brands’ pricing, the warranty on offer is also a key factor.

For instance, you can get something like the Vokera Unica combi with a 5-year warranty. Other brands can offer warranties as low as 2-years — we’d avoid them like the plague.

Realistically, 5 years should be your minimum target for a warranty term. 7 or more years is ideal, but a 10-year term is certainly preferable. You’ll pay a little bit more for a 10-year warranty (£100-300), but on a £3,000-ish installation, we’d take that additional warranty coverage any day.

Ideal Boilers offer combi boilers with a 10-year warranty, and if you need a combi boiler for a 4-bed house, you should be looking at the Ideal Vogue 40.

Likewise, you can get a 10-year warranty on all Worcester and Viessmann boilers. That’s not the norm, but if you jump over to Heatable’s boiler calculator we mentioned above, you’ll find that all Worcesters have a 10-year warranty.

How Much to Buy a Combi Boiler for a 4-Bedroom House?

The price of your installation will depend on the boiler you get (i.e. a budget brand with a short warranty is cheaper than a premium branded product with a long warranty), and  your property details.

We used Heatable’s boiler calculator to get a price on the Vitodens 100-W range from Viessmann, and you’re looking at around the £2,400 mark there, including Gas Safe installation. You’ll see a similar price for something like the Ideal Vogue.

combi boiler for a 4 bed house

If you’ve got high heating and hot water demand (2 or more showers, for instance) and a large heating run with lots of radiators, expect the price to be closer to £3,000 for a boiler with a 10-year warranty, like the Viessmann Vitodens 100-W 35kW.

To get an accurate quote, you can plug in your property details here and get a a range of fixed price quotes on your screen.

How Much Will My New Boiler Save Me on Heating Bills?

If your boiler is still working, you might be on the fence about replacing it. And that’s understandable, given the potential installation costs involved.

The first thing to do is check the energy efficiency rating of your current boiler.

New combi boilers are A-rated, meaning they’re typically over 90% efficient. Older gas boilers could be as low as G-rated; in some instances, this means it’s LESS than 60% efficient. So, for every pound you spend on gas, you lose 40p due to the boiler’s inefficiency.

There’s a quick guide on the Energy Saving Trust which outlines expected energy savings based on your property size, current energy rating, and the energy rating of your new boiler.

Efficient Boiler Upgrade Energy Savings Chart

Long story short, those with a large 4-bedroom detached property and a (terrible) G-rated boiler could be saving around £305 per year. That’s around £25 in your pocket every month, which is around the cost of a new boiler on finance 😊. You can check out the chart below to find out how much you could save.

new boiler energy savings

Note that a new boiler will also provide you with additional benefits, like radiators that warm up faster and showers that are consistently warm. Of course, you’ll also get the peace of mind knowing that you won’t have to pay for boiler repairs for a long while.

Still Not Sure Which Boiler is Best?

If you’re using a local installer, they might offer Worcester Bosch Greenstar combi boilers, they might not. We’ve curated a list of our favourite boiler brands, you should be able to find the best boiler for your home there.

Most local installers price keenly, but to make sure, you can compare their prices to other local installers here.

Or, if you’d prefer, you can get a fixed price online for a boiler with a 10-year warranty here.

FAQs on Best Boilers for a 4-Bed House

Below, we’ll answer a few FAQs about combi boilers for 4-bedroom properties.

How many kW does it take to heat a 4 bedroom house?

Typically, you’d need a boiler with an output of 30kW to heat a 4-bedroom house. That said, it depends on your demand for central heating and hot water, as well as the quantity of radiators.

How many radiators can a 30kW boiler run?

A 30kW combination boiler can be expected to handle 15 standard size radiators without issues. Keep in mind, however, that this number could decrease if you’ve got high demand for hot water.

Can you run 2 showers with a combi boiler?

Combi boilers aren’t ideal for running mutliple showers or taps at the same time. That’s because they supply hot water on demand, and consequently rely on mains water pressure, which often doesn’t suffice. If your household often runs several taps or showers simultaneously, you whould consider getting a system boiler instead.

Can a combi boiler be used in a 4 bedroom house?

Yes, absolutely. A 30kW combi boiler, like the Worcester Bosch Greenstar 4000 30kW is an excellent option for heating systems in a 4 bedroom home.

However, if you’ve got high demand for hot water, you should consider a different type of boiler. For example, a heating system with a hot water cylinder/hot water tank, and a system boiler, is better-suited for handling multiple taps and showers running at once. Asking a heating engineer to come and survey your property is a great way of getting the boiler type and size right.

What’s Next?

Thanks for reading our guide to prices and the best boilers for a 4-bedroom house.

Still got questions? Drop us a line via our contact page, and we’ll get back to you as soon as possible.

Not ready to buy your boiler just yet? Bookmark Heatingforce.co.uk and pop back soon. We constantly update our blog with boiler reviews, price guides, and general advice.




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