Solar Inverter Comparison: Overview, Types & Brands

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What is an Inverter?

The solar inverter is what turns the solar energy generated by solar panels into the useable electricity that powers households. The energy generated by the solar panels is in the form of direct current (DC) energy. DC electricity only flows in one direction and is the type of electricity used to power phones and laptops. The role of the solar inverter in a photovoltaic (PV) system is to convert the DC energy into the useable AC electricity that powers households. The inverters are also connected to the grid, this is important as it needs to be able to handle the flow of AC electricity. As any surplus solar generated electricity is fed back into the grid.

Types of Solar Inverters

There are a number of different types of inverters these being, string inverters, hybrid inverters, micro inverters, and power optimisers. All these inverters perform the same function of converting DC to AC but have different methods and positionings in a PV system.

String InvertersFronius String Inverter

The string inverter is the most commonly used type of inverter for residential PV systems. PV systems with a string inverter have all the panels wired together by one or more ‘strings’ which then connects to the centrally placed inverter. String inverters are typically located outside on a wall of the house. These inverters are best utilised on roofs with consistent unobstructed sunlight throughout the day. The downside to the ‘string’ connection is, if one panel experiences a power drop due to partial shading, for example, the whole string is affected.

ProsCons
Low costPerformance heavily impacted by shade
DurableGenerally limited to simple systems
Easy to maintainInability to monitor individual panel performance
Single point of failure

SolaX Hybrid Inverter

Hybrid Inverters have the same characteristics as a string inverter with the additional feature of a charge controller, this is used to manage a battery system. Charge controllers can also be bought as an additional unit, but hybrid inverters provide the option of an all in one device.

Micro Inverters

Micro inverters as indicated by the name, are small individual inverters that are connected to the back of an individual panel. Enphase micro inverterThey still perform the same inverter function but at each individual panel. This increases the efficiency of the system as in partial shading only the shaded panels are affected, not the entire system. Microinverters also allow for the potential to upgrade the system at a later date. This is due to the system size not being limited by a central inverter, as microinverters can be easily added or changed. Making it easy to replace if one breaks. 

ProsCons
Increased performanceCost
System flexibilityMaintenance
Monitor individual panel performanceElectrical components located on roof
Easy to replace

Power Optimisers SolarEdge Power Optimiser

Power optimisers are similar to microinverters as they are connected to an individual panel. They are not a stand-alone inverter and must be utilised in conjunction with a string inverter, as the DC energy still needs to be converted by the string inverter. Power optimisers are certainly an upgrade from a stand-alone string inverter system, providing additional value at a much cheaper price than the micro inverter.

ProsCons
Increased performanceMaintenance
Monitor individual panel performanceElectrical components located on the roof
Cheaper than microinverters

What Type of Inverter Should I Choose?

A commonly asked question with no single answer. There are a number of factors that are taken into account when considering what type of inverter is right for a PV system.

  • System Size
  • System Complexity
  • Roof Direction
  • Roof Visibility (is there sun obstruction)
  • Budget

If the decision was based purely on efficiency then micro inverters are the obvious choice, but due to the high price they are not feasible for the majority of residential system owners. If the system is simple and the roof is unobstructed from sunlight, then a string inverter will suffice. It’s generally only for complex roofs and roofs that get shading during the day that the options of power optimisers and microinverters need to be explored.

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Two Tests to Determine if an Inverter is Good 

Test 1- Is the Inverter a PV Evolution Labs Top Performer?

PV Evolution Labs (PVEL) with support from DNV GL has been independently testing Solar Panel reliability since 2014, and for the first time in 2019 have tested solar inverters. It is a voluntary test which manufacturers have to pay to be a part of.  The solar panel testing is considered internationally as an excellent indication of solar panel quality. It’s expected that the inverter testing will have the same recognition. Click the heading below to download the full inverter scorecard. 

PVEL 2019 PV Inverter Scorecard

TestingTop Performers
Passive Chamber • Delta M8-TL-US

• SMA SB7.7-ISP-US-40

Powered Thermal Cycling• Delta M80U

• Schneider Context CL-60A

• SMA SB7.7-1SP-US-40

High Temperature Operation• Delta M8-TL-US

• Fronius Symo 24.0-3

• Huawei SUN2000-11.4KTL-US

Low Temperature Operation• Delta Solivia 3.8 TL

• Huawei SUN2000-11.4KTL-US

MPPT Efficiency• Delta M80U

• Huawei SUN2000-30KTL-US

• Schneider Context CL-60A

Conversion Efficiency• Huawei SUN2000-30KTL-US

• Huawei SUN2000-375W-USP0

• Schneider Context CL-60A

Energy Harvest• Huawei SUN2000-28KTL

• Huawei SUN2000-30KTL-US

• Schneider Context CL-60A

AC Operational Envelope• Delta M80U
DC Operational Envelope• Delta M80U

• Schneider Context CL 25000NA

Transient Response• Delta M8-TL-US

• Fronius Symo 24.0-3

• Huawei SUN2000-11.4KTL-US

Ground and Arc Fault• Delta M8 TL-US

• Delta Solivia 3.8 TL

• Fronius Symo 24.0-3

30 Day Runtime Performance• Huawei Sun2000-11.4KTL-US

• SMA SB7.7-1SP-US-40

Test 2- Does the Manufacturer have an Australian Office and Easy Warranty Claim Process?

Relying on your solar installer is not always an option as we’ve seen many residential solar installers (including the large ones) go out of business well within the lifetime of the systems they are installing.

To make sure you have options to claim warranty, Solar Choice recommends:

  1. Visit the Solar Inverter manufacturers website
  2. Make sure they have an Australian office with an office number you can call
  3. Make sure the warranty claim process is clearly outlined on their website

Fronius Office

Industry Standards for Solar Inverter Warranty Periods

Inverter warranties can vary in length, the minimum warranty that should be accepted is 5 years with 10 years being more ideal. An increasing number of manufacturers are now offering the ability to purchase an extended warranty, up to an additional 20 years from certain manufacturers. The list below includes warranties of CEC approved inverter brands and whether they have an Australian office.

Solar Inverter BrandsWarranty Extendable ToAustralian Office
ABB5 years10 yearsYes
Afore1 yearNo
Aiswei (Solplanet)6 yearsNo
Alpha ESS5 yearsYes
Canadian Solar5 years20 yearsYes
Delta5 yearsYes
Enphase10 yearsYes
Fronius5 years25 yearsYes
GoodWe5 yearsYes
Growatt5 years10 yearsYes
Huawei5 yearsYes
SMA5-10 years25 yearsYes
Sofar Solar5 years25 yearsNo
SolarEdge12 years20-25 yearsYes
SolaX Power5 years20 yearsYes
Sungrow10 yearsYes

 

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