Use a thin film array (easy install) and a micro inverter (cheaper, lighter and works better in cloudy location).
So how much electricity will this produce?
So if your have your 300W solar panel in New York (where solar irradiation = 4.49kWh on average annually according to the table), it will generate (4.49kWh x 0.3kW =) 1.347kWh for the day.
So I could in a month produce 30 x 1.347kWh = 40.41kWh
GMP charge $0.14959/kWh so each month I would in theory be generating $6 worth of electricity.
Investment $1200/$6 = 200 months / 12 = 17 years to pay back :-(
The total cost of the system would have to fall to around $500 per each of these to be worth it in my opinion.