You can find more information regarding Fronius and KUBIK 500 inverters:

Fronius inverters for grid connected systems
New inverter for stand alone systems KUBIK 500:
input voltage 12 or 24VDC, output voltage from 10 up to 230VAC,
pure sine wave output at  50 or 60Hz.
Output power: 500VA, that can be increased by parallel connection
up to 3000VA.