Please don’t spread misinformation. Every current Chinese inverter (Sungrow, Goodwe, you name it) can provide emergency power with or without installed battery. My all PV installations (10-20 kWp panels with 10-30 kWh batteries) provide emergency power for whole house. Battery has lower power than the grid connection, but clients agree to don’t charge their EVs during blackout. Starting cost 10000€ for 10 kWp panels and 10 kWh battery if installation is easy on single flat roof.