How to choose the right boiler blog banner

How to choose the right boiler

November 17th 2023


Choosing the right boiler is an important decision, but with all the options available, do you know which boiler is best for you? It is understandably difficult to know which is the best option for your home.

When making this decision, it’s important to think about your current and future heating and hot water requirements. You should consider how much hot water you and your family use, the size of your home and the fuel supply that is available. Also, consider your existing heating system and the types of boilers you can have installed.

Choosing the wrong boiler can cost you both time and potentially a significant amount of money. The wrong boiler can struggle to heat your home or waste energy and needlessly increase your energy bills.

Types of boilers

Before choosing the best boiler for your home, you should know the types of boilers available to you today. By combining this knowledge with your hot water and heating needs, you can choose the best boiler for you. 

Combi boilers

A combination boiler, also known as a combi boiler, combines a water heater and a central heating system in one compact unit.

These boilers are typically installed as a wall-hung unit and provide both heating and water on demand.  Water is heated directly from the mains, so there is no need for an external cylinder, giving you more storage space.

Combi Crossover

Navien UK has introduced the Combi Crossover, a new type of boiler with the same high performance as system boilers with the cylinder-less advantages of compact Combi Boilers.

Our Combi Crossover range puts hot water first, giving you and your family rapid hot water and consistent temperatures. The NCB700 ON Combi Crossover can deliver water to three showers at the same time, so no one in the family has to wait for hot water.

If you’re an energy-conscious family, the Combi Crossover recirculates hot water to reduce your water and energy usage and helps bring your bills down.

System boilers

System boilers feature a separate cylinder for storing water and are designed to provide a constant supply of hot water. This type of boiler is perfect if you live in a large home that requires a greater need for heating.

Regular boilers

A regular boiler, also known as a ‘conventional boiler’ is designed to heat your home and provide hot water using a cold-water tank and hot water cylinder. The cold-water tank feeds the hot water cylinder, which stores heated water ready for multiple outlets to run simultaneously, while the boiler itself delivers the hot water to the central heating system.

Fuel types for boilers

There are a few types of fuel that can be used to heat your home and provide hot water: gas, oil and, soon to be, hydrogen.

Gas boilers

The most common fuel type for boilers is mains gas. Most homes with boilers currently have gas boilers. This offers peace of mind for your home as there is currently a constant supply of gas to homes in the UK.

Oil boilers

An oil boiler, also known as an oil-fired boiler, functions in a similar way to a gas boiler, although its source of energy is oil. There are two types of oil boilers – heat only and combination oil boilers, with the latter being like other combi boilers such as the LCB700, which features an internal hot water storage tank.

Hydrogen boilers

While not ready in the UK just yet, hydrogen boilers are a future solution that will eventually replace natural gas boilers. Hydrogen is a completely carbon-free fuel source and can easily integrate into an existing boiler space with little disruption to your current setup.

In time, boilers will be 100% hydrogen ready where they will be first installed as a natural gas boiler. Once the hydrogen gas infrastructure is in place, the boiler can be converted to hydrogen from gas for you.

Understand your heating needs

The size of your property and the amount of occupants is the difference between needing a smaller boiler like the NCB500 ON Combi Crossover, and having to go for a best-in-class boiler like the NCB700 ON Combi Crossover.

Some boilers are designed for homes with only one bathroom, whereas others are aimed at larger homes with more than three bathrooms and large families requiring hot water from multiple outlets.

You must consider your current situation and any future plans to help choose the right boiler for you.

Sizing your boiler

Having the right sized boiler is important for ensuring enough heat and hot water is circulated around your home. When an installer talks about the size of boiler you require, they are trying to understand your power needs. Boilers are “sized” by kilowatts (kw).

When selecting the right size boiler, think about the number of radiators, bedrooms, and bathrooms you have in your home. Your installer will take you through the technical information to show you how your boiler meets your property requirement.

You should also consider the physical dimensions of the boiler as well. Some boilers are very large, so require plenty of storage space. Your installer will help in measuring your space for your boiler to ensure a smooth installation.


Heating your property costs money, from the initial cost of the boiler to the installation and long-term maintenance. However, purchasing the right boiler with high efficiency ratings and up-to-date technology can drastically bring down your energy bills and make heating your home a smooth process.

Efficiency ratings

If you are a sustainability-conscious household, the environmental impact of your chosen boiler should also be taken into consideration. This is because some fuel sources are more sustainable than others.

While oil and gas should be both as efficient as one another, they are polluters of our atmosphere. In response, the industry is starting to move in a sustainable direction.

Your boiler should have an A+ efficiency rating. If not, there are ways to gain that rating with add-ons like a smart controller.

With the emergence of hydrogen boilers and heat pumps on the market, homeowners are increasingly able to heat their homes with cleaner fuel sources and a clean conscience.

Which boiler is best for my house?

As the size of your home will affect how efficiently a boiler can heat it, you should consider carefully which type of boiler will adequately heat your home.

What is the best boiler for a three-bedroom semi-detached house?

As there are fewer external walls for heat to be lost in a semi-detached house, these types of homes are generally easier to heat than detached homes. We recommend you install a gas condensing combi boiler, where it’s compact design is able to heat water on demand with instantaneous hot water.

What is the best boiler for a three-bedroom terraced house?

Much like semi-detached houses, there are fewer walls to lose heat in a terraced house and as such they are very good at retaining heat. With a one-bath/shower, three-bedroom typically requiring a boiler with a minimum size of 29kW, the NCB500 ON Combi Crossover’s compact design and brilliant power will heat a three-bedroom terraced home with exceptional levels of reliability.

What is the best boiler for a large 5-bedroom house?

Larger houses will likely have more bathrooms and radiators than the average home, meaning that the demand for hot water and heating will be higher. For this type of home, we recommend the game-changing NCB700 ON Combi Crossover, which is able to provide hot water to three bathrooms simultaneously, while providing unparalleled heating efficiency with ON AI technology.

What happens if you choose the wrong size boiler?

Without proper research, you could choose the wrong size boiler for your home. As a result, you could have a lot of unwanted payments, in the form of energy wastage and possible faults from improper use. Many boilers come with a long-term warranty, so read up on the terms and conditions to see how you will be covered in the event of a fault.

When using a qualified installer, such as those found in the Navien installer network, they will advise on the best option for your home and ensure that the correct boiler is professionally installed. To get in touch with a Navien installer, use our Find an Installer’ tool today.


There are many considerations to take into account when homing in on the perfect boiler for your home, including your heat usage and the size of your space. It’s very important to choose the right boiler for your home to ensure that your home will be sufficiently heated and that you won’t be needlessly paying for wasted energy. For more help with finding a boiler that’s perfect for your home, use our find a boiler tool or get in touch today.

More news articles...

How to choose the right boiler blog banner

Nov 17th 2023


How to choose the right boiler

Choosing the right boiler is an important decision, but with all the options available, do you know which boiler is

Oct 25th 2023

Case Studies

A successful NCB700 ON installation in East Sussex

A customer of ours in East Sussex needed a boiler that was powerful enough to keep up with the day-to-day

Navien boiler in a kitchen cupboard

Case Studies

Heating ON three floors

When a customer of ours found that a competing boiler was not up to the task of heating their large

Customer Service