Solar Facts for South Africa

Written by James Rolf

 

What is a Solar Inverter? (short version)

An inverter is one of the main components of a solar or battery backup system. It is a box that converts battery energy to mains electricity. In South Africa the most common brands are Sunsynk, Tesla PowerWall, Victron, SMA and a lot of Chinese brands.

 

What are the main factors in choosing an inverter?

Deciding on a solar inverter for your solar power system depends on several factors, including the size of your system, your budget, and your specific needs and preferences. Here are some things to consider when choosing a solar inverter:

1. System size: The size of your solar power system will determine the size of the inverter you need. Make sure to choose an inverter that is compatible with the size and type of solar panels you are using. Most households and small businesses in South Africa can get by with 5kW inverter.

2. Efficiency: Look for an inverter with a high efficiency rating, as this will ensure that your solar power system is generating as much electricity as possible. Note that inverters also use power when they are in standby, expect 50W standby. This is really important at night because a 50W inverter will chew through 0.6kWh from your batteries by doing nothing (12 hours x 0.05kW).

3. Type of inverter: There are several types of solar inverters available, including string inverters, microinverters, and power optimizers. Each type has its own advantages and disadvantages, so research and compare different options to determine which type is best for your needs.

4. Brand reputation and reliability: Choose an inverter from a reputable brand with a proven track record of reliability and customer satisfaction.

5. Warranty: Look for an inverter with a solid warranty, as this will protect your investment in case of any issues or malfunctions.

6. Cost: Consider the cost of the inverter and how it fits into your budget. Keep in mind that higher-priced inverters may offer better performance and reliability, but may not be necessary for smaller or less complex solar power systems.

7. Function: if you want to programme your inverter to do smart things, then you will need an inverter where that option is available, like a Victron.

8. Offsite monitoring: very useful for those "I left the pool pump on" moments.

9. Noise: solar inverters needs cooling fans that are rarely quiet. Don't put one in your bedroom. There are often warning tones from an inverter such as warning of excessive power usage. It is useful to hear the warnings while in the kitchen as the kitchen has many appliances that can overload a domestic inverter.

 

What is the best inverter for a home in South Africa?

This depends entirely on your circumstances. Most systems are 5kW to 10kW for residential and small businesses in South Africa.

 

What is a Solar Inverter? (long version)

A solar inverter, also known as a photovoltaic (PV) inverter, is a device that converts the direct current (DC) electricity generated by solar panels, or batteries, into the alternating current (AC) electricity that is used in most homes and businesses. Solar panels produce DC electricity, but most electrical appliances and devices run on AC electricity, so the inverter is a crucial component in a solar power system.

The solar inverter typically has several functions, including converting the DC electricity produced by the solar panels into AC electricity, synchronizing the AC electricity with the grid or with the building's electrical system, and optimizing the performance of the solar power system by tracking the maximum power point of the solar panels. Some solar inverters also include monitoring and data collection features that allow users to track the performance of their solar power system over time.

There are several types of solar inverters available, including string inverters, microinverters, and power optimizers. Each type has its own advantages and disadvantages, depending on the specific needs of the solar power system.

 

Problems with solar inverters

Businesses often run very different type of appliances from residential users. Where businesses fall short is often on electric motors starting up. Why is this a problem? Electric motors require much more power when starting up than when they are running. It is not unusual for an electric motor to pull 4 times more power than it's rated power on start up. This is a problem for appliances with electric motors like fridges, saws, ventilation fans, air conditioners and the like. You will need to specify an inverter that is much larger than the motors, so if you have a 2kW fridge motor, you will need an inverter that is at least 8kW, and preferably 10kW, to be able to start it. Most inverters can deliver more than their specified power output but typically only for a spike of a few milliseconds whereas motors typically draw higher power for a few seconds on start up.

Inverters for retail businesses with large fridges need to be careful, especially when starting the fridges to make sure that they don't all start at the same time.

If your inverter is tripping the inverter, it may be time to check up on the motor capacitor. It is also possible that the motor capacitor is not the correct size for your electric motor. Check common capacitor sizes here for electric motors.