Equipment and components
Inverter
Also known as: solar inverter, photovoltaic inverter.
Definition
The inverter converts the direct current the panels produce into the alternating current used by your home or business and by the grid. It is the most intelligent component of the system and is usually the first to need replacing during its service life.
Converting direct current into alternating current is only its most visible task. The inverter also continuously searches for the panels' maximum power point (MPPT), adjusting voltage and current to extract the greatest possible output at every instant; it synchronises its output with the grid's frequency and voltage; it monitors output and records the history; and it executes the electrical protections, including automatic disconnection when the grid goes down.
That automatic disconnection (anti-islanding) is a safety requirement, not a defect: it stops a system continuing to inject energy into a grid that technical staff believe to be de-energised. It is the reason a grid-connected system without batteries stops working during a blackout, even though the sun keeps shining.
It is also the component with the shortest service life in the set. While panels are guaranteed for 25 years or more, an inverter's warranty is usually considerably shorter — with the option of extending it — and its replacement should be allowed for in the project's economic analysis. When comparing quotes, the inverter's brand, warranty and after-sales support matter as much as the panels'.
The essentials of Inverter
- It converts direct current (DC) into alternating current (AC).
- It optimises output through maximum power point tracking (MPPT).
- It disconnects automatically if the grid goes down (anti-islanding protection).
- Its service life and warranty are shorter than the panels': plan for replacement.
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Frequently asked questions about Inverter
Why doesn't my solar system work during a blackout?
Because the inverter of a grid-connected system disconnects for safety when it detects the grid has gone down, so as not to inject energy into lines where technical staff may be working. To have power during an outage you need a hybrid system with batteries and a backup output.
How long does a solar inverter last?
Less than the panels. It is an electronic device with components that age, so the norm is to allow for at least one replacement over the life of the system. The factory warranty varies between brands and can usually be extended; that figure should be explicit in the quote.
What inverter capacity do I need?
It is sized in relation to the panels' peak capacity, and it is not always identical: it is normal to install somewhat more panel capacity than inverter capacity, because modules rarely deliver their nominal value. The installer calculates that ratio based on local radiation and the string configuration.
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