A combination boiler, usually known as a combi boiler, is a compact unit supplying heating and hot water straight from the mains supply. Its efficiency and small footprint have made it a favoured option among homeowners.

There are numerous models available and the task of choosing the best combi boiler can be overwhelming. Our team of experts have rigorously evaluated and ranked various boiler brands and models, examining their capabilities, features, and prices to guide you in the right direction, helping you make a more informed choice.

We thoroughly analyse and score 35 specific factors to ensure our findings are unbiased and dependable. The boiler’s performance across these factors forms the basis of its overall rating and underpins our reviews.  

Everything we test falls within one of the following categories, and we carefully adjust the importance of each factor based on its significance in identifying the ideal combi boiler. 

  • Performance and features
  • Provider/installer performance
  • Value for money
  • Customer experience

The combi boiler features we prioritise

We think the critical factors in determining a combi boiler’s quality are:

  • Energy efficiency
  • Performance and reliability
  • Features
  • Durability and build quality
  • Installation process
  • Manufacturer 
  • Cost
  • Warranty
  • Customer support
  • Aesthetic appeal

Energy efficiency

A combi boiler with high energy efficiency operates more cost-effectively, using less fuel to deliver an equivalent level of heat and hot water. This efficiency leads directly to reduced energy expenses which add up over the boiler’s lifetime. Such boilers also emit less carbon dioxide (CO2), lessening their environmental impact.

Performance and dependability

The performance of a combi boiler refers to its capacity to produce heat and hot water efficiently and steadily. A top-performing boiler can rapidly warm your home to the desired temperature and maintain a consistent hot water supply. This is crucial during the colder months when the demand for heating escalates.

Dependability denotes the boiler’s proficiency in consistently delivering its functions over an extended duration without malfunctioning. An unreliable boiler can reduce or eliminate access to heat or hot water and could result in expensive repairs. 


Features such as programmable thermostats, intuitive interfaces, and smart home system compatibility can improve the user experience. For example, programmable thermostats allow you to set the heating to come on before you come in from work, creating a comfortable, energy efficient home.  

Some boilers also incorporate features tailored for specific needs, such as frost protection for areas experiencing extreme cold or solar panel compatibility for households with solar systems. 

Safety considerations hold equal, if not greater, importance. Combi boilers are engineered with a range of safety features designed to avoid issues such as gas leaks, overheating, or excessive pressure accumulation, all of which can present significant hazards. 

Durability and build quality

A combi boiler with a durable design and high build quality will likely have a longer lifespan. This means you won’t need to replace the boiler as often. The unit will maintain optimal functionality over an extended period, providing consistent heat and hot water supply without frequent breakdowns. 

A high build quality generally indicates the components used in the boiler are more robust and resistant to wear and tear. 

Installation process

Some combi boilers are easier and quicker to install than others, and that can result in less labour and installation costs. It also minimises the disruption to your household routine, which can be crucial for many homeowners. 

We research the entire installation process of every combi boiler we review.


The manufacturer’s reputation and track record can offer valuable insights into the anticipated quality and dependability of the boiler. Manufacturers enjoying a solid market reputation usually maintain rigorous quality control procedures, resulting in products with consistent performance and fewer complications.


In evaluating cost, it’s vital to consider not just the initial purchase price of the combi boiler, but also the long-term operational expenditure. A less expensive boiler may appear tempting at first, but if it’s less efficient and pricier to operate, the total cost over the boiler’s lifespan could be higher. That’s why it’s crucial to factor in the boiler’s energy efficiency and anticipated maintenance costs when calculating the cost.


A warranty protects the buyer against a faulty or broken boiler, assuring that the manufacturer or supplier will rectify or replace the defective parts without extra charge.

Without a warranty, the homeowner might have to bear the total cost of any necessary repairs, which could be substantial. A warranty is designed to cover these expenditures, making it a key component in the total cost of owning and maintaining a combi boiler.

Customer support

Quality customer support provides clear and accurate guidance on using and maintaining your combi boiler.

A strong customer support team generally implies that the company stands behind its product and is prepared to assist if something goes wrong. However, if you need to make a warranty claim, customer support should provide a streamlined claims processing service.