Solar all-in-one inverters also fit the bill, they hook up to AC for charging and you can prioritize AC over battery for redundancy. Solar isnt required. You c

Solar all-in-one inverters also fit the bill, they hook up to AC for charging and you can prioritize AC over battery for redundancy. Solar isnt required. You can get 3kw ones for around $800. Just add your own 48v battery.