Solar Inverters Explained

A solar panel string inverter converts direct current (DC) of a solar panel into alternating current (AC). As seen in this diagram, it is the final piece of a PV system. From there, the electricity gets transmitted to end devices for consumption.

Solar inverters are the most demanding part of a solar system and unfortunately also the one most likely to cause problems. This is not a surprise, considering that inverters are usually located outdoors and exposed to harsh weather conditions such as rain, humidity and extreme heat while generating thousands of watts for up to 10 hours a day. Therefore, it is important to use a quality inverter and mount it in a protected location.

Choosing the Right Inverter

It is crucial to choose an appropriately sized inverter to optimise the efficiency of the solar panel system. Consequently, inverter input capacity should be at least as high as the combined output wattage (Wp=Watt peak) of all connected solar panels. Long-lasting systems require a high quality inverter with a robust convection cooling system.

The required output capacity of the solar power inverter heavily depends on the purpose of the system. For example, independent off-grid systems that cover the entire daily electricity demand of a household require high-capacities (15+ kW). Conversely, on-grid inverters for solar panel systems can do with a lower capacity (15 kW or less) if the user only wants to cover part of the total power demand.

Solar PV Inverter Types

• String solar inverters: String solar inverters are the most common type of inverter. They are connected to a string of solar modules that are wired in series.
• Hybrid inverters: A hybrid inverter or inverter charger combines a solar inverter and a battery inverter in one simple device. Most of them can also provide basic backup power during power outages. These inverters are becoming more competitive as hybrid inverter technology advances and batteries become cheaper and more attractive.
• Off-grid inverters: Off-grid or stand-alone systems require powerful battery inverters with built-in chargers that can be set up as either AC or DC coupled solar systems. Off-grid systems usually require powerful pure sine wave inverters that yield the same output voltage form as the public grid.
• Micro inverters: Micro inverters are very small solar inverters that connect directly to individual solar modules. Because each micro-inverter and module operate independently, they are a good option for complex roof layouts and sites with shading issues. Despite their slightly higher cost, micro-inverters are the most popular inverter type in the US and Canada.