My application is home office with primary power source being solar charging to battery, then an inverter to provide house/office power from batteries. When battery levels drops below voltage required to provide power, need it to switch into line power mode and at a set time (after sunset) to switch the battery to full charge mode. At sunrise the inverter needs to switch back to battery again. This could also be done by simply switching OFF (to Line power)at 10.5 (or as low as possible where it could still provide full power to outlets) and switching ON(battery) at 12.5 volts. This configuration and variants of it will be very popular. Adding a GRID-TIE would be a huge jump, with Batteries as stand by power only. Other options would be automatic start/stop to a generator.