What is an Inverter?
Kristopher Roscoe - October 11th, 2009
Inverters are used in grid tied systems and in off grid systems to convert direct current (DC) to alternating current (AC). AC current is what is used in your house and the AC current can be fed back into the grid. The inverter automatically shuts down during a power failure. This prevents current flowing back into a "dead" grid and electrocuting a utility line worker.
Typically, the inverter is the single most expensive piece of equipment in the Photovoltaic system. They also have the shortest warranties, usually 10 years. Usually it's just a small rectangular box that is placed on the main feed coming from the array. In Philadelphia, they are usually mounted in the basement, close to the PECO electric meter or electrical panel.
It is very important to look at the effciency when purchasing an inverter. A grid tied inverter should be above 90% effceincy.