Hi,
The NREL PVWatts calculator will do 1 or 2 axis tracking in addition to a fixed array.
It takes into account your location and local weather.
It gives monthly output, so you can see both the when and how much benefit tracking has.
http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/Seems like it would be worth running both cases for your area.
Just as a quick check for my area (Billings, MT)
Fixed, horizontal 2KW array Output: 2146 KWH/yr, July 302 KWH, Dec 58 KWH
Two axis tracked 1KW array Output: 1869 KWH/yr, July 228 KWH, Dec 93 KWH
I just used 1 and 2 KW arrays for easy numbers to plug in -- you can enter whatever your exact panels are for your case.
Horizontal is good in summer, but very poor in winter -- especially at higher latitudes.
Seems like an array that stows flat and just tilts up to a fixed tilt with fixed azimuth might be a reasonable compromise?
Gary