So going grid connected. Any feed in tarrifs from your energy provider?
current power usage (average daily would be best).
How much are you looking at generating? enough to not have a power bill, enough to keep the bills down?
Currently in Australia where I am, to get a zero power bill (mostly thanks to the high access charge), on a 14KHW per day usage (one person, gas heating), using current feed in offers,I would need a solar setup of about 6KW worth of pannels, which would be about $15,000K AUD at last check. Works out to be about a 11 year cost/break even period (ie: 11 years before I start to save money).
but my north facing roof (being in the southern 1/2 of the world) is not large enough for that number of pannels. I would need a support setup to hold the pannels, which increases setup costs.
Best bet if after information is to call some of the local solar installers for your area and have a copy of your power bill on hand for working out the size you would need.