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Navien LCB700 Blue Flame Combi Oil Boiler

Available in internal and external models, the Navien LCB700 Combi comes in a range of outputs to suit your needs.

Are you looking for an oil combi boiler? The LCB700 Blue Flame Combi from Navien could be the perfect boiler for your home. Suitable for homes of all sizes, this boiler pushes the boundaries of condensing oil boiler technology and boasts revolutionary blue flame technology that guarantees superior efficiency and ultra-low NOx emissions. It also achieves the highest 3-star mark in domestic hot water performance and is the first in the UK market to offer an A+ energy rating. 

How Much Does this Boiler Cost?

The Navien LCB700 Combi comes with a 21kW, 28kW or 36kW output and costs between £2,200 and £2,675, not including installation. All models are available in interior and exterior options, and the external units are slightly more expensive than the internal ones. Oil combi boiler installation costs vary, so we recommend getting a quote from different local and national installers to find the best price. Always ask for a fixed-price quote, and only contact installers who are OFTEC approved.  

How will I know if this Boiler is Suitable for My Home?

The internal and external LCB700 Combi boilers are floor-standing units that come in a range of outputs to match your requirements. These oil combi boilers from Navien don’t require tanks in the loft or a hot water storage cylinder in the airing cupboard, making them ideal for homes where space is limited. If you have high hot water demands, you will probably need the system or regular version.  

If you’re unsure whether an oil combi boiler is a good fit for your home, you should consult a qualified heating engineer. In addition to advising you on the correct boiler type for your home, they can help you determine what boiler size will meet your heating and hot water requirements. 

Is it a High Efficiency Boiler?

Yes. The Navien LCB700 Combi is a 93% efficient A-rated boiler. It benefits from Navien’s latest heat exchanger technology that maximises heat transfer for super efficiencies. With the Navien Smart Plus thermostat, this combi boiler is 98% efficient and increases the ErP rating to A+. 

Does this Boiler have a Good Range of Controls and Features?

Navien’s LCB700 Combi has several impressive features, like a stainless steel heat exchanger to increase the boiler lifespan and blue flame technology that guarantees superior efficiency and ultra-low NOx emissions. It has a full-text driven control panel that lets you manage heating and hot water temperatures and informs your engineer how efficiently your boiler performs. The built-in control panel also shows you how much fuel you’ve used to save you from checking the oil tank. Both interior and exterior models have smart casings and offer an Intelligent Mode that monitors your hot water usage and prepares it according to your typical usage routine. 

How long is the Warranty on this Boiler?

The Navien LCB700 Combi comes with a generous 10-year warranty as standard to give you total peace of mind. 

Summary of Important Information

  • Expect to pay between £2,200 and £2,675
  • Heating output of 21kW, 28kW or 36kW
  • Hot water flow rate of 14, 18 or 20 litres per minute
  • Internal models dimensions: 860mm (H) x 600mm (W) x 600mm (D)
  • External models dimensions: 900mm (H) x 673mm (W) x 650mm (D)
  • Uses oil as its fuel source
  • A-rated for efficiency
  • 10-year warranty as standard

Pros and Cons

Navien’s LCB700 Combi has a lot going for it and boasts impressive technology and features. All you need to do is weigh up the advantages and drawbacks to decide whether this oil combi boiler is the one for you. Below are the pros and cons of getting this boiler installed. 


  • Suited to small, medium and large-sized homes with one bathroom
  • Internal and external models
  • Blue flame technology – guarantees superior efficiency and ultra-low NOx emissions
  • Stainless steel heat exchanger – prevents corrosion and helps extend the lifespan of the boiler
  • Built-in Intelligent Mode – monitors hot water usage and prepares it according to your typical usage routine
  • Achieves highest 3-star mark in domestic hot water performance
  • Class-leading flue lengths of up to 20 metres and IPX5 rating – siting flexibility
  • Smart control panel – gives you full control of heating and hot water temperatures
  • OpenTherm ready – gives instant access to the latest control technology
  • Compatible with Smart Plus controllers – regulates heating according to changes in outside temperature and enables geofencing via an app to let your location automatically take care of your heating
  • Self-diagnosis and error feedback feature – offers a quick troubleshooting guide
  • Combined pressure relief valve and condensate drain – fast and simple installation
  • Provides maximum energy efficiency – reduce fuel bills and carbon emissions
  • Great rating on Trustpilot – correct at the time of writing – February 2022
  • 10-year parts and labour warranty


  • None
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