48v 100ah battery with Bluetooth BMS built in is around 700$ on ali express... Slightly more direct from Amazon in the USA if you want it fast. Will store close to 5kwh which I guarantee you beats out this solution. Of course you'd still need to buy the grid sync inverter (available in many places) as well as a solar mppt charger and solar cells. Still will come below this cost - or you'll simply blow by the capacity of what you would have paid for this solution. But gotta have the old noggin on straight to do it yourself.