Different types of inverters under the Sun

Solar inverters take direct current (DC) generated by your PV array and translate it into alternating current (AC). This procedure is an obligatory step because virtually all home appliances run on AC. Thus, a solar inverter plays an essential role – it prepares your solar harvest for consumption.

It would be wrong to state that DC to AC conversion is all that inverters do. Most modern models can also be called the brain of the system. They monitor and analyze performance of various system components, including solar panels, batteries and even EV chargers. This functionality allows users to cut costs, improve efficiency and speed up problem detection and repairs.

Solar inverter is the single most vulnerable part of your solar setup. If any other equipment fails, be it batteries, charge controller or even some of the panels, the system will most likely continue generating energy. However, should the inverter stop working for some reason, it will render the whole solar panel system unusable, even if everything else is perfectly fine. This is because technically the inverter is powering your home, not the panels.

True to their name, string inverters work with strings, i.e. sets of interconnected solar modules. A residential string inverter is a rectangular box not taller than a chair. Usually it has 3-6 inputs for strings up to 12 panels each. Most devices are stackable, meaning you can use more than one in your solar setup.

Grid-tie inverters is what most people imagine when they hear the phrase ‘solar inverter’. Most residential customers embrace this solution for its affordability and simplicity. At the same time, grid-tie inverters enable Net Metering, which greatly reduces the payback time. One major disadvantage of grid-tie inverters is that they can’t function during a power outage. When there’s no power in the grid, you won’t have electricity in your house, even with solar panels on the roof and the sun in the sky.

Central inverter sometimes simply means a grid-tie string inverter. The term is also used to describe utility-scale enormous boxes that work with dozens of strings as opposed to just 3-6 in a residential unit. This solution tends to be cheaper than using multiple smaller inverters, but further centralization significantly increases risks. Shading or other technical problems will affect not only all other modules in the same string, but also a number of other strings. In case of failure hundreds of panels may stop generating, and units of this size are harder to replace.

Hybrid string inverters are a very diverse group. The word hybrid simply refers to multimodality, so you can’t expect all inverters labeled as hybrid to share the same features and functionality. The term isn’t strictly defined, which allows manufacturers to call an inverter hybrid if it has some additional function besides DC to AC conversion. It could be anything – from the ability to charge an electric vehicle to an integrated charge controller. In some cases hybrid inverters are meant for completely distinct applications, like on- and off-grid.

Hybrid on-grid inverters are no different in appearance from grid-tie devices, but they make your PV system more flexible and truly independent. These inverters allow you to store solar power for later use, for example, during peak demand hours or in case of a blackout.

You can often see articles comparing grid-tie, off-grid and hybrid inverters as if these were completely different categories. The truth is that most off-grid inverters are also hybrid. They can’t export the excess energy into the grid, but often can use it to charge the batteries. What makes them hybrid is an ability to run both from solar panels and batteries, while plain off-grid inverters depend on batteries only. That’s why they are also sometimes referred to as inverter-chargers.