What is the latest price of 500kW Grid tie Inverter?

I want to use 500kW Grid tie Inverter for emergency power supply to the system from 12V or 48V DC battery bank.The output is of 230V AC from the Inverter to use in office as emergency power supply. So i would like to know the price, efficiency and advantages of the inverter on Grid tie system as emergency power... show more I want to use 500kW Grid tie Inverter for emergency power supply to the system from 12V or 48V DC battery bank.The output is of 230V AC from the Inverter to use in office as emergency power supply. So i would like to know the price, efficiency and advantages of the inverter on Grid tie system as emergency power supply when grid fails?
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