Combining Grid power and solar power

Normally a typical grid tied (utility interactive) system goes both ways but it does what you want. If there is enough sun to cover your load than you don't buy any utility power. If you have more sun than your current load, it sends power to the utility which typically gives you a credit for the extra power you are producing. If there is not enough sun to cover your load, than the utility supplies you the difference. 

Of course anytime that you hook power generating equipment to the utility, you need an agreement with the utility and the equipment needs to be installed to the National Electrical Code (NEC)and the interconnecting inverter will have to meet certain standards.

What is the device that supplies the difference power from the grid

Thanks a lot for ur answer.

This is what I exactly want.

From your words I understood that, it is the inverter which supplies the offset power when there is a deficiet from the solar.

Can you please specify some of those inverters which do these functions. Also I need remote monitoring of the inverter.

Yes of course it is the grid that supplies the deficit, but what i am asking is whether the inverter is able to calculate the deficit and take from the grid if the solar/battery power is not sufficient?

If it is the case please specify me the inverter companies which are having that option.