Category - Boilers
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Will Scholfield, Engineer

20 May : Updated 20 May ● 5 min read

Navien NCB 300: boiler review

When you're looking for a new boiler, the sheer variety and amount of options available to you can leave you feeling confused.

Well, fear not; BOXT is here to be your Gas Safe registered knight in shining armour. In this boiler review guide, we'll explore one of Navien's most popular combi boilers, the NCB 300.

Founded in 1978, Navien boilers are sold worldwide and they are the fourth largest global boiler manufacturer.

The company's success comes from its reliable, efficient and cost-effective appliances. All Navien boilers undergo rigorous two-stage inspections involving over 250 separate quality checks, so you can be confident you're buying a boiler that's built to last.

Having said this, Navien is a relatively new name in the UK market, so they've not yet established their place in the boiler industry over here as they have in America and Asia.

To help you make an informed decision regarding upgrading your central heating system, we've rated the Navien NCB 300 in key categories, such as energy efficiency, reliability, cost and performance. But first, let's explore the boiler's key features.

Need to get your Navien boiler fixed or serviced?

Need to get your Navien boiler fixed or serviced?

With BOXT, you can get a Navien boiler service from just £8.99 per month. If you need to get your Navien boiler fixed by a Gas Safe registered engineer, we can help with that, too. 70% of repairs are diagnosed and fixed within the one-hour inspection­. Repair visits start at £89, and we could be with you as early as tomorrow. We’re rated excellent on Trustpilot­.

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Navien NCB 300: key features

The Navien NCB 300 comes in various sizes, including 37kW and 41kW, but we're focussing on the 28kW appliance in this review. Key features of the NCB 300, which we explore in more detail below, include:

  • Designed for small and medium-sized properties
  • Smart weather forecasting and geofencing using information from the Met Office
  • ErP efficiency rating of 93% (A-rated)
  • 5-year parts and labour warranty
  • Smart heating technology
  • Stainless steel heat exchangers for optimum durability

Navien NCB 300 review

Since first coming to the UK in 2014, Navien has become a trusted name, and the NCB700 model won the Domestic Heating Product of the Year at the Energy Saving Awards in 2022. 

But how does the company's NCB 300 model fare in important areas like reliability, performance and cost? Let's see...

Navien NCB 300: Reliability

While not as established as other boiler brands, such as Worcester Bosch or Vaillant, Navien boilers have been recognised for their consistent and reliable performance.

While the 5-year warranty may be shorter than those offered by competitors on equivalent appliances, the warranty documentation does cover labour. 

In terms of Trustpilot reviews, Navien is rated great, with an average rating of 3.9 out of 5 from over 140 reviews.

With the average lifespan of a boiler being 15-20 years and Navien only entering the UK market in 2014, it remains to be seen just how reliable the boilers are in UK homes. But, with features like the stainless steel heat exchanger, it's clear that the Navien boiler is built to last.

Reliability score: 3.5/5

Navien NCB 300: Efficiency

Navien designs all of its boilers to be highly efficient, reducing your energy usage and the appliance's impact on the environment. The Navien NCB 300 boasts efficiency levels of 93% and an ErP rating of A; however, this increases to a staggering 98% (ErP rating A+) with three Navien Smart Plus room thermostats.

The 93% efficiency level means that just 7p of every £1 you spend on heating will be emitted through the boiler's flue.

Another benefit of the NCB 300 is its condensing technology, which is specially designed to ensure optimal performance and reduce fuel consumption.

Efficiency score: 5/5

Navien NCB 300: Performance

The NCB 300 28kW offers hot water at a flow rate of 11.5L per minute, providing small and medium-sized homes with effective and reliable levels of hot water and heating throughout the year.

When used alongside Navien’s smart controls, you can access several other convenient and efficient features, including geofencing technology, which tracks usage and understands when you're not at home, adjusting settings accordingly. This contributes to energy efficiency and reduces energy bills.

Similarly, zone control systems can easily be integrated with the NCB 300, which lets you control different areas of your home separately. The main benefit of this is that it gives you greater power over your heating system by allowing you to reduce the heating in rooms you're not using.

Performance score: 4/5

Navien NCB 300: Cost

In terms of prices, the Navien NCB 300 is one of the most cost-effective boilers on the market. 

When you buy from BOXT, our fixed price alsoThis price includes a wireless thermostat and timer, a carbon monoxide alarm, and a system cleanse and filter to ensure your central heating system is free of dirt and debris that could otherwise affect or damage your new boiler.

If you're looking for a new boiler, we can help. Simply answer a few questions about your home and current boiler system, and we will recommend suitable boilers to meet the needs of you and your home, with a fixed-price quote including installation.

Cost score: 5/5

Navien NCB 300: Ease of use

The NCB 300 boasts an easy-to-use interface that makes controlling the temperature a breeze. The display will also clearly tell you if there is a problem, like low system pressure.
This is particularly useful for first-time buyers, who may not be au fait with boiler information and controls.

If you have a compatible smart thermostat installed, you can control and monitor the boiler’s performance via the thermostat’s associated app, using real-time data. These insights enable optimal efficiency and allow you to choose between increasing the heat output or maximising energy savings.    

Ease of use score: 5/5

Final scores

In our review of the Navien NCB 300, the boiler scored a respectable final score of 22.5/25. In particular, the boiler's cost and efficiency stood out as offering exceptional value for money.