Is it true that you can get 4kwh per day per square meter? My average electricity consumption is ~15kwh/day, so if I can potentially offset most of my grid usage with just 4 square meters of solar panel, that seems very attractive. I live in a tropical country btw.
Each of my panels has a theoretical capacity of 390 Watts per hour. So 4kwh in a day seems very feasible. My panels are certainly not the cutting edge of technology!
Your 390W is if the sun is in the zenith and hitting your panel at right angle. Also, are you sure your panel is 1m^2?