Solar Inverter Guide

Solar Inverter

A fundamental part of every Solar Power setup is the Inverter. It is a piece of equipment that is very important to understand.

After you read this definitive guide, you will understand:

What is an Inverter?

Hybrid string inverter

In simple terms an inverter  converts DC power  (Direct Current) into  AC power  (Alternating Current). DC flows in just one direction , this is ideal for Solar Panels because you need it to simply absorb the sunlight and push it through the system in one direction. It might be an oversimplified explanation but for now, that’s all you need to know for the purpose of this article.

 AC flows in both directions , all of your appliances are powered in this way.

Now we have that out the way, let’s move on to the next part.

How do they Work?

The energy from your Solar Panels or your Batteries is fed to the inverter, which then, in turn, handles that energy by transforming the DC power to AC.

You get three main types of Inverters you can use. Each one functions a bit differently from the other:

Grid-Tied, Off-Grid & Hybrid Types

Each inverter has their own set of requirements:

Off-Grid Inverters:

  • Grid or no grid connection
  • Solar Panels optional
  • Solar Batteries required

Grid-Tied Inverters:

  • Grid connection required
  • Solar Panels required
  • No batteries

Hybrid:

  • Grid connection optional
  • Solar Panels optional
  • Solar Batteries optional

Off-Grid Inverters

Off-Grid Inverter

Features

  • Easy to install
  • Expandable
  • High or low voltage options
  •  Lowest solar inverter price 

A very  popular choice because of their price , compared to previous Off-Grid inverters, they are far easier to install due to the fact you have everything in one box instead of separate components.

However, in previous years, an Off-Grid inverter was simply a metal box that only had one function: convert DC to AC. You would need other components like an MPPT (this allows you to connect to solar panels), a Charge Controller (that allows you to connect to batteries), a monitoring device, and a bunch of wiring to tie it all together. Now, you get all of this in one box!

Expandable

 Some Off-Grid inverters can be paralleled  should your demand for more power increase. But, it is essential to remember to do your research and ask questions about how to meet your needs and future plans

High or Low Voltage

You get  2 main types of Off-Grid inverters, and these are Low-voltage and High-voltage . The difference between the two comes down to how many solar panels you can connect to the inverter, more detail on how that works in this guide.

Unlike the Grid-Tied or Hybrid options, most Off-Grid inverters require batteries.

Pros

  • Easy to install
  • Expandable and modular
  • Affordable

Cons

  • Less reliable than a Hybrid
  • Lifespan isn’t that great (around ten years)
  • Can be noisy

Hybrid Inverters

Hybrid inverter

Features

  •  Newest Technology 
  • Multiple MPPT inputs
  • Scalable
  • Flexible

New Technology

The  newest in inverter technology , the Hybrid Inverter offers everything you’d need in an inverter and then some.

Multiple MPPT Inputs

Most Hybrid inverters will come with  two or more MPPT inputs[/su_highligh] and a   high voltage range , allowing you to have a more extensive array. In addition, you can  split your array  so that you have two arrays that function independently. Separate arrays mean that should one fail, you still have another fully functioning array.

Scalable

The Hybrid Inverters can be paralleled, which is an excellent feature if you plan on scaling up in the future. They communicate with most Lithium-ion Batteries, and most Li-ion batteries are parallalable too. Above all, If you need a  system that can grow with you , this is most definitely the inverter to go for.

Flexible

Another great feature of the Hybrid Inverter is the ability to  power non-essential loads  should your solar power production exceed the needs of your essential load. To clarify, this means that any  extra solar power produced can then be used for your non-essential appliances .

Finally, the feature that makes the Hybrid Inverter genuinely exceptional is the ability to  blend power from multiple sources . It will always use the available solar power generated from your array, and if your array is not producing enough, it will  pull power from your batteries and the Grid . This feature ensures that you always have power and that you use the available solar-generated power first and foremost before using your batteries and the grid.

The Fusion inverters are the ideal Hybrid inverters, and we highly recommend these.

Pros

  • Efficient
  • Easy to install
  • Blends AC/DC Energy
  • Long-lasting (around 15 years)

Cons

  • More expensive

What Size Inverter Do I Need?

Different size inverters

We have a formula that we’ll show you so that you can work out your inverter size and so that you understand how the sizing works. 

Firstly, you’ll take your average monthly electricity bill amount and divide that by 2.2 (the average price per kW) Eg: 

Monthly Bill

R1800

/

Average Price Per kW

R2.20

=

Monthly Usage in Kw

818.18kW

 

Secondly, take your monthly usage in kW and divide that by 30 (days in a month)

Monthly Usage in Kw

818.18kW

/

Days in a Month

30

=

Daily Usage in kW

27.27kW

 

Lastly, take your daily usage and divide it by 5.5 – the hours in the day that you produce the most. 

Daily Usage in kW

27.27kW

/

Max Production Hours

5.5

=

Production Needs

4.96kW

 

You will need at least a 5kW inverter to cover the 4.96kW

  • 6   x 400W Solar Panels will cover around 48% of your usage.
  • 10 x 400W Solar Panels will cover around 81% of your usage.
  • 12 x 400W Solar Panels will cover around 97% of your usage.

In addition to size, you will also need to consider MPPT voltage ranges when selecting an inverter. 

Do you need a large array? If the answer is yes, you will need a high voltage inverter.

If the answer is no, you can look at the low voltage inverters. 

You can read up more on how to size an array here: How to Size a Solar Panel Array

Inverter Application Questions:

It is also important to figure out what your end goal is:

  • Do you want an inverter for solar power or load shedding only?
  • Will you add solar panels later?
  • Will you add extra solar panels later?
  • Will you need batteries?
  • Will you be adding another inverter later?
  • Do you require a UPS function?
  • Do you have Single Phase or 3 Phase supply?

All of these questions are important and will also help you make the right decision and prevent you from spending extra money down the line. 

As a general rule of thumb, we suggest a hybrid inverter for all applications, especially if you need a UPS function and when you are planning on adding solar panels because this is an investment that will save you money in the long run. 

But, if you are only looking for a load shedding kit with no plans on expanding or adding panels later and do not require a UPS function, then an off-grid inverter will work for you.

Solar Inverter Prices, How Much Do They Cost?

The cost of a solar inverter all comes down to brand, build quality, features, and size.

For commercial inverters that have a massive kW rating, you will be paying over R50,000.

Whereas residential inverters typically starting from a 3kW to a 10kW inverter, you can expect the following price ranges:

  • Off-Grid Inverters between R 8,000.00 and R 14,000.00
  • Hybrid Inverters between R 18,500.00 and R 44,000.00

Whatever the choice, it's always best to start where you can, saving you money in the long term and having the ability to re-jig your system as time goes on.

Best Solar Inverters in South Africa

To name the best pound for pound brand is tricky. Each brand does have its strengths and weaknesses, depending on its application.

Here are the best brands that we would recommend:

  1. Fusion - Technology has been around for a long time, good quality Hybrid inverters
  2. Goodwe - this Hybrid brand is of great quality and a great price

Resources:

https://en.wikipedia.org/wiki/Solar_inverter

3 comments

  1. Anonymous

    Visitor Rating: 4 Stars

  2. Visitor Rating: 5 Stars

  3. Nikola Batev

    Good day,
    I would need some advice and pricing.
    In January i bought 16 365W solar panels, 3kVA RCT 48V Inverters x 3 and four Pylon-Tech U 2000 batteries.
    During the installation ALL three inverter did blow up – incorrect installation by some company from Brakpan – CHC Electrical. So – now I am looking for the new inverters. I wold like to go for 5kVA – two f them. I would need a quote from you and advice – which ones can I install, how many solar panels can they take and – most important – can I split the system in two – one 5kVA + 2 Pylon Tech batteries and join them…or would you advise something else.

    1. Hi

      Sorry to hear about the inverters blowing up, your choice of 5kVa inverters sounds like a better option but before suggesting anything what kind of appliances/machines are you running and what is the maximum kW’s are you dealing with?

      If you’re looking for high end inverters that handle large loads and spikes we suggest the Victron inverters, if however you are dealing with moderate loads and spikes we’d would suggest an inverter from our Hybrid range or for the lower end of the end we suggest the Kodak (Voltronic) range.

      Thankfully you have PylonTech which are a good brand with a decent compatibility range.

      Give us a call or email us to advise further.

  4. Anonymous

    Visitor Rating: 4 Stars

  5. Visitor Rating: 4 Stars

Comments are closed.

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