Grid tie converters take your solar energy and converts it to match the energy that is being used in your house(DC to AC). It all so can feed energy back into the the electric company and will actually lower your meter but you may want to cheek local laws for your areas on this subject. Using a grid tie converter can save you the hassle of having an electrician come in to rewire every thing to match what your solar power is bringing in. One drawback is that if you loss power from the electric company the converter will shut down but if you have back up batteries charged this can hold you through this time lets say at night or a cloudy day when your not getting enough energy from your solar system. I recommend you keep track of the waits that you are using in your household before investing in a converter. While looking on ebay I found a 1000 Watt grid-tie inverter...Mppt Tracking for $1,189.00.
Here is a very informative video on grid tie inverters and what they do and how they work.
GRID TIE INVERTER SOLAR POWER EASY SOLAR SOLUTION POWER INVERTERS
Well I like the fact in the video that he demonstrated running the grid tie converter but to bad it was a cloudy day I would like to have seen it run directly off his solar panels instead of car batteries.