How Solar Works Inverters
The inverter is the component that converts DC power into the AC that runs most electronics.  The two main types of inverter we deal with are Grid-tied and Off-grid.  Grid-tied inverters take power directly from the solar array and feed it onto the utility grid.  Off-grid inverters take power from a battery bank and power devices.
Grid-tied inverters are selected based on the wattage of the solar array.  The panels are organized in combinations of series and parallel to match the voltage and current handling characteristics of the inverters.  For example a system consisting of twenty 250W panels for a total of 5000W would use a KACO 5002xi inverter.  If all the panels were in series, the voltage would be too high.  If all the panels were in parallel, the voltage would be too low.  By using string sizing software we can determine that there should be two strings of ten panels to operate efficiently with the inverter.
Another type of inverter is the micro inverter.  This is when each panel has its own inverter and inverters are connected to each other in parallel.  For these inverters, only certain panels can be used that match the voltage and current requirements of the inverter.  Since grid-tied inverters only feed power to the grid and not to certain devices, the size of your load does not matter in system design.
Off-grid inverters draw their power from the battery bank, therefore it doesn’t matter how many or what type of panels are used in the system.  Off-grid systems are designed around the total wattage of all the devices they would power.  For example, if you have a 1200W microwave and 800W of lights, you wouldn’t want to use an inverter with an output of less than 2000W.
Another important factor to consider when selecting an off-grid inverter is whether you need pure sine or if modified sine will work.  Pure sine is identical to what comes out of an electrical outlet, with smooth oscillations from positive to negative.  Modified sine is a square wave with instantaneous transitions.  If the device that the inverter is powering has moving parts like motors or refrigerator compressors, pure sine is needed.  Otherwise, if the inverter only powers lighting or chargers, modified sine will be sufficient.
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