Delta Solar Inverters: An Independent Review by Solar Choice

Delta logo

Overview of Delta – company history

Delta Group, headquartered in Taiwan, was founded in 1971 and focusing initially on the production of switching power supplies. Over the last 50 years they have expanded into power electronics, industrial building automation and energy infrastructure projects. In 2019 the Delta Group posted an annual profit of AUD$1.1 billion, so they have a secure financial backing.

In 1999 Delta commenced the development of their first 260W grid-connect inverter for the German market. They now manufacture solar inverters from 2.5kW to 140kW and distribute across the world with local websites and offices set up in the USA, China, India, Japan, Korea, Thailand and Australia. Their Australian office is located in Notting Hill, Victoria.


A brief rundown on solar inverters

A solar system’s inverter is the point at which the DC electricity produced by solar panels is turned into grid-compatible AC electricity. Typically, there are 2 approaches to inverters – either string inverters or micro-inverters.

String inverters (including all of Delta’s product range) have traditionally been the standard in the solar industry. They send the power produced by solar panels to a central inverter that changes it from the DC electricity to the usable AC electricity that powers homes. Delta also specialises in hybrid string inverters which provide the ability to charge a battery as well as use solar power immediately as its created.

Micro-inverters, generally a more expensive solution, provide a small inverter for each solar panel that is installed. This means that each panel operates individually which creates more visibility over performance and can offer some advantages in partly shaded conditions


Delta Inverters – Point of difference

Delta H5A_222Delta manufactures single-phase inverters with one or two MMPTs (Maximum Power Point Tracking), three-phase inverters with dual MMPTs, and hybrid storage inverters with 2 MMPTs and a 6kwh battery. All of the CEC approved Delta Inverter range are Transformerless Inverters, which contributes to the high efficiency.

Delta’s home series, the major series for residential application, is designed for supplying power with a capacity of 2.5kW to 5kW. In addition, the E5 hybrid inverter with a battery option is also included in this collection.

The Delta H5A_222 inverter (5kW) is one of their most popular models designed for residential applications. The inverter features an impressively low start up voltage of 35V, compared say Fronius’ equivalent 5kW inverter which starts at 80v. This means that the Delta inverter will run longer in the early morning and late evening. Whilst in the short run the difference won’t be significant, over the life of the system the savings will mount up.

Although not useful in most typical applications, this inverter is one of the only options where you can generate the electricity utilising only one panel. Most inverters require at least three or more panels to generate electricity.


Some of Delta’s inverters were named as a PV Evolution Labs Top Performer

PV Evolution Labs 2019 Top Performer InvertersPV Evolution Labs (PVEL) are well known for their independent tests of Solar Panel performance. In 2019 they also commenced testing solar inverters. Their testing procedure is voluntary for solar inverter manufacturers to participate in, so not all inverter models are tested. However it is an excellent proof point for inverters called out as top performers.

To see the full PVEL scorecard results click here.

In 2019 the some of Delta’s inverters ranked as a top performer in the following 3 tests:

Testing Category Top Performers
Passive Chamber • Delta M8-TL-US
Powered Thermal Cycling • Delta M80U
High Temperature Operation • Delta M8-TL-US
Low Temperature Operation • Delta Solivia 3.8 TL
MPPT Efficiency • Delta M80U
AC Operational Envelope • Delta M80U
DC Operational Envelope • Delta M80U
Transient Response • Delta M8-TL-US
Ground and Arc Fault • Delta M8 TL-US• Delta Solivia 3.8 TL


How much do Delta solar inverters cost?

Delta inverters on the Austarlian market are manufactured in China and have reached a significant scale of production meaning they are able to offer cost-effective prices at approximately 23c per watt.

Indicative pricing

Solis Inverter Model Indicative Price Range
Delta-H5A_222 5kW $1,000 – $1,300
Delta-RPI-M10A 10kW $2,300 – $2,600
Delta-RPI-M30A 30kW $3,600 – $3,900

Keep in mind that inverter costs generally only run between 10-20% of your total system, so often it is worth investing in a high-quality inverter given this will have a large impact on the efficiency and performance of your Solar Power project.

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Delta Inverter Efficiency

An important aspect of getting the most value out of a solar inverter is to choose an appropriately sized inverter to optimise the solar panel system efficiency. To read about the importance of inverter sizing and system efficiency click here.

Residential inverter efficiency standards are generally 95 to 98 per cent. Delta inverters are towards the top end of this range with at least 97.5%  listed as their ‘maximum efficiency’ throughout their full product range.

A number of Delta models have over a 98% max efficiency, including the Delta RPI 4.99kW (RPI commercial series M6A). This Dual-MPTT string inverter has a 98.3% max efficiency, making it one of the most efficient options for small commercial projects.


Delta Inverter Warranties

In Australia, all CEC approved Delta inverters come with a minimum of a 5-year manufacturer’s warranty. Most inverters in Australia come with either a 5 or 10 year warranty included so this leaves Delta towards the shorter end. Customers do have the option of purchasing an additional five years of warranty directly from Delta and installers can purchase an extension of up to 15 years total on behalf of their customers.

If customers experience any warranty-related issue, the original installer who installed the system should be the first line of support for replacing or repairing the product. However, Delta also suggests that customers who can no longer contact their original installer should contact their warranty department on 1300 335 823 or filling the form on their website to get the support from their local office in Australia.


Major range of Delta Inverters available in Australia 

The majority of Delta’s Inverters (under the name of Delta Electronics Inc) are approved by the Clean Energy Council for the Small-scale Renewable Energy Scheme, which is Australia’s home solar rebate program.

The following Common residential Delta Inverter Series & sizes are CEC approved:


Delta Solar Inverters Pros and Cons


  • Performed well in independent testing completed by PV Evolution Labs
  • High efficiency with close to market leading performance
  • Delta have an Australia office with local support staff


  • Standard 5 year warranty is less than competitors who offer 10 years
  • No case studies in Australia for larger scale commercial projects


Comparison of Delta Solar Inverter specifications (common models)

Delta 3kW 


Delta 4kW 


Delta 5kW 


Rated AC Power Output 3kW 4kW 5kW
Phases Single-phase Single-phase Single-phase
Maximum Continuous Output Current 14.3A 18.6A 23A
Number of MPPTs 2 2 2
Maximum Inverter Efficiency 97.5% 97.5% 97.5%
Dimensions  380*318*130 mm 380*318*130 mm 380*318*130 mm
Weight 9.7kg 10.5kg 12kg
Warranty 5 Years 5 Years 5 Years
Operational Temperature Range -25°C to 60°C -25°C to 60°C -25°C to 60°C
Made in China China China


Should you use a Delta inverter on your project?

Given their performance in independent testing it seems clear that Delta inverters are high quality across a number of different areas. The financial strength of the Delta Group and the fact they have an office in Victoria, provides some confidence that you won’t be left stranded if something goes wrong.

For those reasons we believe that Delta are a great choice for your project, especially with a warranty extension up to 10 or 15 years.


Example of a large-scale Delta Inverter Project 

  • Site: Vandel, Denmark
  • PV System: 113.1MWp
  • Inverters: 1508 units of Delta’s M50A inverters
  • Total CO2 saved: 46,410 Tonnes annually

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Reviews from Australians who have installed Delta Inverters

Rated 3.00 from 3 reviews
4th May 2022
6kW system

Impossible to reset Wi-Fi connection for cloud service monitoring. Very poor, very disappointing. Looking to have the inverter remove and replace with one with a better monitoring function.

11th February 2022
SA - 5401
5kW system

No problems with the inverter. I have an app on my phone which allows me to monitor the inverter's performance.

30th July 2021
VIC - 3754
10-15kW system