It could be that easy but it would serve you well to dig a little deeper into your energy usage to optimize the system. If your base load is around 250w/hr and you produce the full 1200 then you sending almost 1kwh back to the grid for free meaning you bought an extra 2 panels for nothing.

If your baseload is high, like 2kw/hr or more if you have an ev charger or pool pump or whatever but that load is mostly on the other phase then it is essentially the top scenario again. (There are two phases, L1 and L2 in the US so if ev charger is L2 and your plug in solar is L1 then there is no offset).

The ideal system will have a battery and a smart meter so you can really offset usage as much as possible and especially during on-peak time.