Add there losses on battery charging and downconversion from grid, night time charge keeping, and you can easily get 40-50% more, so 2-3kWh is really optimistic

Add there losses on battery charging and downconversion from grid, night time charge keeping, and you can easily get 40-50% more, so 2-3kWh is really optimistic, aim at 6-7kWh, and that's on wired charger.