Solar inverters are as important as the actual solar panels. They’re the devices responsible for converting direct current (DC), the energy that solar panels generate, into alternating current (AC) electricity for electrical uses in our houses. DC needs to be converted since it has a constant voltage that only travels in a single direction. In contrast, AC electricity flows in both directions allowing electricity to travel over long distances in the circuit. Our previous article titled ‘System to Store Solar Power for Over a Decade’ discussed how current research is now finding ways to maximise the use of solar energy by developing a system that can store solar power, and this includes an efficient solar inverter.
Since inverters convert and optimise electricity outputs, it’s important to know the difference between the three main solar inverters:
The most common type of solar inverter is a string inverter. Also known as central inverters, string inverters connect all solar panels into one single inverter, which converts solar power into usable electricity. As the oldest and most common type of inverter, string inverters are reliable and inexpensive, making them favourable among those unsure about which solar inverters to use. Since string inverters connect multiple solar panels, they are centrally located in one place in your house, which is convenient for monitoring, repairing, and replacing them.
However, string inverters are less efficient at optimising solar energy output. Shading on one solar panel will affect the power output performance of the entire string because all solar panels are connected to only one inverter. Lastly, string inverters only provide total-system monitoring, which can be a disadvantage when diagnosing issues with your solar panel system at home.
For safety and financial reasons, some homeowners prefer detailed information about their solar panel systems. David Kuchta outlined how monitoring devices can help you determine how much power your system produces daily, monthly, or yearly. These will track the efficiency and operation of your solar power system.
Microinverters work by converting DC to AC directly from the back of each solar panel. With this, each solar panel has its solar power output level. Besides worrying less about your solar power output performance, you can easily expand your setup with microinverters since you only need to install the inverter on the back of the new panel. Moreover, microinverters provide panel-level monitoring of the entire system. Therefore, it’s easy to trace and diagnose any issues.
Some downsides of microinverters are that they are more difficult to replace than string inverters. Since each solar panel has a microinverter, you have to replace them one by one when they malfunction. Lastly, they are the most expensive type of solar inverters on the market. However, Hoymiles explains that microinverters yield better results than string inverters as they can produce 5% to 30% more solar power, making them more efficient than other solar inverters. Also, if shading is your primary concern, microinverters can quickly minimise the impact of shading through its module-level Maximum Power Point Tracking technology, which electrically isolates solar panels from each other.
Last but not least is power optimisers. It is the perfect combination of string inverters and microinverters. Power optimisers are installed on the back of each solar panel, like microinverters. However, instead of converting DC to AC on the spot, power optimisers condition DC electricity before being converted into AC electricity at the string inverter.
Power optimisers can also reduce the amount of power loss brought by shading. Since they condition the DC electricity produced by individual panels before reaching the string inverter setup, it will not degrade the output of the entire string. Moreover, power optimisers provide both panel-level monitoring and system-level monitoring. With this, homeowners can monitor each solar panel down to the smallest details and have an overview of the entire solar panel system. They are relatively less expensive than your usual microinverters despite having the benefits of a microinverter.
However, the disadvantage of power optimisers is that they require additional power optimisers and string inverters if you need to expand your solar panel system in the future. You may also have difficulties replacing your existing power optimisers since they are located on the roof.
There’s no such thing as the single best inverter. Solar Magazine’s guide to solar inverters elaborates on the factors you need to consider, such as shading and solar array design, before deciding which solar inverter works for you. In conclusion, the perfect solar inverter will depend on your household energy usage and available budget.