be aware of a number of the fact that you will probably need some certification before you can actual use it. If you just build your own, I think you can afford the costs that go with tha certicication process. If you do this for professional reasons, inform yourself properly, because in different countries, the rules can be different.
Also, you need to foresee a system that disconnects the inverter from the mains if the mains voltage disappears (for safety of the workers on the grid).
Stefaan