Homeowners Professionals

Buying a new boiler [A central heating system guide]

Buying a new boiler may not be the most exciting purchase, but it’s certainly an essential one.

Just like when you buy a new car or a big holiday, there are lots of things to consider and, while some compromises may have to be made, you want to be happy with your final purchase. The same can be said when buying a new boiler. There are lots of different options available, from combis to conventionals, electric to gas, and more. The options available to you may change depending on your budget, the size of your home, how many people live in the house and even where the boiler will be located.

It can be a minefield, but don’t panic! This guide is here to talk you through the sea of varieties available so that you can pick the most suitable one. Type, size and make are all aspects to consider, and your choice will impact how efficient your heating system is. Selecting the right boiler for the job could save you money year on year.


Tip #1: Know the types of boiler available

TThere are three main types of gas boiler to consider:

  • Combi (combination)
  • Conventional
  • System

To find out which one is right for you, we’ll be discussing each boiler type in depth, providing both advantages and disadvantages of each.

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Combi boilers

Combi boilers are the most popular type of boiler in the UK and they make up over half of all new boilers being fitted. A combi is an all-in-one boiler solution that operates as a highly efficient heating   and hot water boiler. They don’t need a separate hot water cylinder, which means they’re great for smaller homes or homes with less space.

A combi boiler  works by heating water directly from the mains instead of drawing cold water into a tank that’s usually located in the loft (in the case of a conventional boiler, which we’ll come on to later). This means you can get hot water on demand without the risk of ever running out. Without a cold water tank, the costs of installation are reduced, as well as the cost of materials.

Their small size means that they’re perfect for installing within a kitchen cupboard. They run quietly but are still powerful enough to deliver all of your heating and hot water needs.

It’s important to note that combi boilers deliver water at mains pressure, without the need for a separate pump or power shower. While this is a good thing if the mains pressure in your area is quite powerful,  areas with lower pressure  could find that the water exiting the taps or showers is quite weak. This will be affected further if multiple taps or appliances are on around the house.  

Conventional boilers

Conventional boilers are generally found in older properties. They are the perfect boiler for homes where there is a high demand for hot water or in buildings where there is a large number of bathrooms.  

These kinds of systems do require space for a hot water cylinder, where the heated water is kept until it is needed, and a cold water tank, where fresh water is pulled in and stored, ready to be heated. In some cases, an immersion heater can be added too, so if your boiler breaks down for any reason, you have a backup hot water supply.

While offering an effective solution, the hot water cylinder and cold water tank could be a problem for small homes, and this is why combi boilers have increased in popularity. Once the hot water in the cylinder has run out, you would need to wait for the boiler to heat more water, meaning you may need to exit a cold shower and wait for 30 minutes for more hot water, for example. Generally, this won’t be an issue, as you can programme the thermostat to preheat the water at set times. If your household tends to have showers in the morning, you could set the boiler to begin heating water at 5.30am, for example, ready for everyone’s 7am shower.  

System boilers

A  system boiler  works on the same principles as a combi boiler, heating water directly from the mains. However, a system boiler also has a domestic hot water storage cylinder.

This means that a system boiler is the ideal choice for households that consume a lot of hot water, allowing multiple hot water taps to be used at the same time with little to no impact on water pressure.

It’s very important to get the sizing correct for a system boiler, or you may find that the tank isn’t big enough to store all the hot water you need.  

Tip #2: Know your heating and hot water demands

Now that you understand the three main types of boiler available to you, you should work out how much hot water you use to see which system is right for your house. Below, you can find three different house sizes, as well as the  size of boiler they need  based on average hot water use for the property size and which boiler type is best.  

  • Small terraced house, flat or bungalow

For these smaller builds with one to two bedrooms and up to 10 radiators, a 26-30kW boiler is recommended.

  • Medium terraced house, semi-detached house or bungalow

For these medium-sized builds with up to four bedrooms and 15 radiators, a slightly bigger boiler is recommended at 26-30kW. A DHW storage boiler could be the most advantageous as it won’t take up too much space but will still meet your hot water needs.

  • Large semi-detached or detached house

For a large house with four or more bedrooms and up to 20 radiators, a 30-35kW  system boiler is recommended. This will be able to store hot water for when you need it with no reduction in water pressure when using multiple appliances.

Tip #3: Know your budget

When you buy anything in life, there are always cheaper and high-end options available. The same can be said for boilers, too. There isn’t just one set price and before you can make any decisions about which make, model or type you’ll go for, you need to know your budget. Setting this in advance can prevent overspending.

Boiler prices generally depend on the brand, the type of boiler (combi, conventional or system) and the size of the boiler. Generally, a combi boiler will be the most reasonable, and system or conventional choices could be pricier. You should also take into consideration that the installation cost will not be included in the price of the boiler.

Tip #4: Pick a location

Picking a location for your boiler is important as this could impact the type of boiler you choose. If you’re replacing like with like, then this won’t be an issue. If you wish your boiler to be hidden in a kitchen cabinet, then you’ll likely need a combi boiler that’s small enough for this. It is worth considering the location of the boiler to allow the shortest possible flue run to avoid excess costs when installing large flue systems for removal of waste gases.

Any flue fitting must conform to manufacturing installation instructions and gas safety regulations.

Tip #5: Look into warranties

The length of warranty may impact your decision when buying a new boiler. Boilers can be a significant investment, and you want to make sure that it’s covered should anything go wrong within the first few years of ownership. Most boilers come with a warranty, but the length of these can vary from two to 12 years. The longer the warranty, the better, so do your research to find one that suits you.

Tip #6: Know where to buy a boiler from

Once you’ve decided what type of boiler you need and how much you’re willing to spend on it, you can start shopping for the appliance. There are different approaches to doing this, as we outline below.

Buy a boiler online

You may want to research your options and make your purchase online. This puts you in the driving seat and gives you total control over the appliance you end up with. Although this approach might seem a little daunting initially, you don’t have to be an expert to ensure you choose a suitable product. Online tools are available that narrow your search to help direct you to the most appropriate boiler for your home.

When buying over the internet, make sure you find a reputable provider that offers high-quality appliances. It can help to look at customer reviews as part of this. Also, factor in details such as how and when the boiler will be delivered and who will install it. It is advisable to arrange installation when you purchase as this will help to ensure the process of getting your new boiler is seamless.

 Ask your heating engineer for help

If you don’t feel confident going it alone, you can ask a Gas Safe-registered heating engineer for assistance. They will be able to make recommendations based on their technical knowledge of the appliances available, taking into account the requirements of your home. If you go through one of these experts, they will take care of the installation.

Final thoughts

As with any purchase, there are always pros and cons. This will be the same with your chosen boiler system. The important thing to do is pick the one that has the most pros and suits your family’s needs the best.

If in doubt, contact a local Gas Safe engineer who will be able to advise you on which boiler type is most suitable for your property. They have a wealth of knowledge and experience that could prevent you from making the wrong purchase. Alternatively, use our below tool to see which boiler is best for you. 

Use our below tool to see which boiler is the right option for you. 

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