Intertie/Back-up Photovoltaic Inverter

Greetings Everybody,

I've been looking for a PV system that will work as both an intertie system and a back-up system for my house. The idea would be to generate power during day time that displaces utility contribution of household load. Excess energy produced should be stored in batteries rather than sold to the grid for use during short utility outages and/or house load exceeds power produced. Needless to say, the system must stay on-line during a utility outage.

The main reason for wanting to store energy over selling it to the utility (dispite the obvious efficiency cost) is that agreements with the utility are hard to come by in Puerto Rico and I'd rather store the energy for a rainy day than loose the opportunity.

Is such a system possible/available that anybody knows of??

Regards...