Stripping bloated solar inverter technologies back to basic DC to AC energy conversion is seemingly where the Delta Flex range of solar inverters are making their mark. As a proven solar inverter manufacturer, Delta is now supporting an extremely minimalist design in the Flex range over previous models and like for like rival inverter technologies. With such a refined package, why does the Delta Flex fly below the radar of many?


Make and model:  Delta Flex

Variants:  2.5 | 3 | 4 | 5 kW.

  Design, Performance.


.First Impressions…the Delta Flex is compact. Second impressions, it’s light. What’s missing? Definitely not a dependable heat sink which is a big positive within any fanless, convection cooled solar inverter design. Therefore, has the Delta Flex compromised in areas where alternative inverter manufacturers of similar technologies are hesitant to?


Potentially one of the more exciting string inverter technologies made available in recent years. Complimented by a phenomenally large heat-sink for its size, the new-release all-weather IP65, fanless design of the Delta Flex is yet to win any significant industry awards to date but should provide much competition with such an innovative package. As the modern-day interest of many, battery design compatibility is achieved via both AC or DC coupling through select technologies.

Download the Delta Flex datasheet here:

Delta RPI H5A Inverter


Flex - Design
  • Hybrid with UPS battery compatibility.
  • New release.
  • Fanless.
  • No awards.
  • CE Reihnland certified.
  • Standard.
  • IP 65.


Despite the reduced overall size, the Delta Flex inverter range isn’t short of the prominent features many desire. Dual Multiple Power Point Tracking (MPPT) assists with solar array optimisation. Although, falls short of an advanced shadow management protocol onboard. Aiding fewer points of failure, the multifunction LED only interface supports local App connectivity for detailed inverter production insight eliminating the need for the less dependable LCD interface. Remote data access is achieved either through an inbuilt WiFi module or Ethernet.

Expanded features to further enhance the Delta Flex range for personal suitability exist through the likes of 1st party expanded monitoring capabilities and rapid shutdown options. Manufacturer supplied module-level optimisation options are not available although can be achieved using a 3rd party device such as the Tigo Energy TS4-O. Those seeking a particular installation requirement must note that an inbuilt DC isolator is absent.

Delta RPI H5A Inverter


Flex - Features.
  • 2 MPPTS.
  • LED & APP internet connectivity.
  • WiFi & Ethernet inbuilt.
  • No manufacturer supplied module-level optimisation options.
  • No manufacturer supplied module-level rapid shutdown options.
  • Manufacturer supplied expanded monitoring options.
  • Nominated shadow management protocol onboard.
  • Installer remote access support is rated at - advanced data


As an excellent performer is where the Delta Flex range makes its mark. Weighted European efficiency is among a superior class with 96.8% efficiency. Further complimenting the respectable efficiency is a wide operating temperature range from -25oC up to +60oC (-13oF to +140oF), while derating occurs beyond +40oC (+104oF). Weight and noise emission criteria are both outstanding. The lightweight 12kg package that is the Delta Flex is barely noticeable sound wise emitting no more than no more 20 db(A). Where won’t the Delta Flex perform?  Installation locations greater than 2000m above sea level or environments likely to exceed 95% humidity.

Delta RPI H5A Inverter


Flex - Performance
  • 98% European efficiency.
  • Temperature range of -25°C (-13°F).
  • Temperature range of +60°C (140°F).
  • Temperature derating of 40°C (104°F).
  • Weighs 12 kg (26.4lbs).
  • Noise emission of 25 dB (A).


Ranking inline with an average inverter warranty, 5-years, the Delta Flex offers little in the way of excitement from a manufacturer guarantee perspective. Warranty extensions are available to purchase, however, with no manufacturer trained installer network and should the installation fail to  meet manufacturer specifications, the warranty could be as worthless as the paper it’s printed on. Not to be discouraged, the Delta Flex holds a trustworthy warranty against industry alternatives if installed correctly.

Delta RPI H5A Inverter


Flex - Guarantee
  • 5-year parts warranty.
  • 5-year service warranty.
  • No authorised installer network.


As with most inverter manufacturers they are Hardware manufacturers first. Software manufacturers second. Although a consistent evolution on the positive side is a progression in the right direction nonetheless. 

View the full Delta Monitoring Portal review here > (Coming Soon).

Delta RPI H5A Inverter


Flex - Software
  • SEMS Monitoring Portal.
  • iOS & Android app.
  • Alerts & fault diagnosis.


As they say, you get what you pay for. The Delta Flex presents on the more expensive side when compared to alternative like makes from the same manufacturing region, however, delivers a lot more in comparison. Worth paying a little more for.

As a gauge, Delta Flex H5A 5 kW inverters are available online from:

 USD 1000  |  AUD 1400  |  EURO 900 

Excludes taxes, shipping and installation.

Source – Google

Delta RPI H5A Inverter


Flex - Affordability
  • Good technology score.
  • 5kW approx for $1000 USD ex.


Seeking a dependable inverter technology built to perform without having to break the bank? The Delta Flex range may just be the perfect fit. The minimalist and modern design encourages end-user appeal while presenting exceptional performance at a more affordable level. As a global superpower in robotic engineering, Delta has delivered to the international solar market an inspiring inverter technology which most should consider.


EM - Overall
  • Design 3.8
  • Features 3.8
  • Performance 4.3
  • Guarantee 2.3
  • Software 3.0
  • Technology 3.5
  • Affordability 3.7

Have a question?

Don’t be shy, leave it below and a Solar Review community member will respond with the insight you need.


How was the score for the Delta Flex calculated? By utilising the Solar Review Inverter Assessment Criteria V2.3 >

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  1. I great admirer of your team work and the content.

    Since i stay very far from your place, is there anyone who can give insight to one more company launched in India with 5 kw solar invertor Havells “Enviro GTi5000D “(5Kw), it’s rating and performance.


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