Both the solar inverter and the charge controller sit between the solar system and the rest of the off grid system but they work in different ways.
What Exactly is a Solar Inverter?
A solar inverter converts the solar power directly into 240 volt AC electricity. This means that during the day, when the sun is out you can use the power in your house directly from the solar panels – without cycling your batteries.
To charge the batteries they need to be paired with a compatible battery inverter. This pairing is called AC coupling because they link with AC electricity.
What Exactly is a Charge Controller?
The charge controller takes the DC solar power from the panels and directs it towards the battery for charging. The main function is to regulate the power that goes into the batteries so that they don’t overcharge. This is why they are sometimes called regulators.
The power stays in the DC format from the panels to the batteries and it only gets converted to 240 volt AC electricity via the battery inverter when you want to use it in your house. It is called DC coupling because the DC solar panels couple with the DC charge controller to charge the batteries.
What is the Difference?
The charge controller is DC coupled and the solar inverter is AC coupled.
Which is Better?
There are different reasons why you would choose one over the other, and there is a good argument for having both options in the one system.
Generally speaking though, DC coupled systems are more cost effective for small domestic stand-alone power systems, whereas AC coupled systems are more cost effective for larger domestic options.