The difference between a off grid inverter and a grid tie inverter is an off grid inverter converts stored energy from a solar battery bank and converts or inverts the stored electrical energy in to AC household current. A grid tie inverter on the other hand takes solar or wind energy as it is produced and stores it in an electrical grid. Inverters from Outback (GVFX and GFX) and Xantrex (XW) can be used as grid tied inverters with battery backup. We do not recommend using the Outback GVFX/GFX inverters in off grid applications as it will have trouble accepting the rough AC power from a back up gas or propane gen set.
Off grid inverters and Dual function inverters from Outback Power and the Schneider Electric XW inverters all have built in battery chargers. Cotek and Samlex inverters do not.
Grid tied inverters can be classified into two sub categories under string inverters and micro inverters. String inverters have the solar panels wired in high voltage series strings. Some string inverters now incorporate several string inputs to avoid the power loss associated with shading issues. The micro inverter systems overcome this disadvantage by having each solar panel with its own dedicated inverter and so keeps power losses from shading to a minimum.