Navien NCB 300

Answer a few quick questions about your home to get a fixed price for a Navien NCB 300 with finance available.

Get a fixed price quote

Supplied & installed from £1,790

Installed as soon as the next working day*

We'll beat any like-for-like price

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

Get the Navien NCB 300 on an all-inclusive plan

Get your new Navien NCB 300 installed, plus annual servicing and unlimited repairs for a fixed price from only £33.35 a month. When you choose our stress-free, all-inclusive BOXT Life boiler plan you benefit from:

- A new A-rated boiler installed

- Annual services for 10 years

- No callout fees

- Unlimited boiler repairs for 10 years

- Fix or replace

- No deposit or price rises

Get a quote

BOXT customer reviews of the Navien NCB 300

Easy order system. Great customer service who went through everything with me. Ordered [Navien 300]. Delivered. Fast instalment date. And Boxt was the best price by far.

Jane Hayles

Great experience from start to finish. Ordered on Monday, fitted following Thursday. Fitting engineer went above and beyond, kept area clean well worthy of 5 stars!! Had Navien combi boiler fitted.

Paul Fitzsimons GB • 1 review

I had a new boiler fitted through BOXT [Navien], price point was much cheaper than other companies, easy to select boiler through their website.

Miss Charlotte Sim

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.

BOXT Limited is authorised and regulated by the Financial Conduct Authority. FCA register No. 767308. Finance is offered through HomeServe Finance Limited (FRN 994955) and in some cases we also lend with Propensio Finance Limited (FRN 806409). Finance available subject to status, affordability and a credit check. Terms and conditions apply. BOXT Limited acts as a credit broker and is not a lender. Registered in England & Wales company No. 08086606 VAT No. 257059782. BOXT Limited, 3320 Century Way, Thorpe Park, Leeds, West Yorkshire, LS15 8ZB.