Navien NCB 300
Finance available
Answer a few quick questions about your home to get a fixed price for a Navien NCB 300 with finance available.
What makes the Navien NCB 300 so good?
Exclusively designed by BOXT, built by one of the world's largest boiler manufacturers. This powerful model has the performance and hot water flow rate to match Britain's best-selling boiler.
- Up to 5 year warranty
- BOXT's best selling boiler
- Available in 30-41kw
- Combi boiler
- Available in gas or LPG
- A rated efficiency
Included as standard with your Navien NCB 300 installation from BOXT
All installation and labour costs included in your fixed price, so the price you see is what you'll pay
5 year manufacturer-backed warranty, that we register for you
12 month workmanship guarantee, covering all work carried out by our engineer for a full year after installation
System flush, to ensure your heating system is in the best health possible for your new Navien boiler
Magnetic filter, to keep your new Navien boiler healthy and efficient for longer
Carbon monoxide alarm, helping to keep you and your family safe
Wireless thermostat, to easily control your heating on a schedule that works for your home
BOXT customer reviews of the 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. Navien is rated Excellent, with an average rating of 4.4 out of 5 from over 441 reviews.
Efficiency
Navien designs 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.
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.
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.
Check if the Navien NCB 300 is right for your home
*Next working day installation when you order before 3pm, subject to availability.
All prices are correct as of October, 2025.