SOLAR PANEL OUTPUT ESTIMATION
As a rule of thumb, in the middle latitudes, a solar panel will generate as much as 50% of its rated capacity per day. This means the solar panels, for each will produce an average of about 300 mA per hour or about 2.4 Amp-Hours per day. This is more than adequate for an installation that will only be powering a weather station. If other devices need power, such as a radio modem, you will need to refine your estimate. The most accurate way to calculate solar power potential is to obtain historical data for the site showing the typical solar radiation over the course of a year. Look at the time of year when the solar radiation produced per day over a 2-week period is the least. This is the worst case period and will produce the least amount of power from the solar panel. If you estimate the average solar radiation per hour during this period, you can then estimate how much power the home solar panels for each will generate. Assume that the sun averages about 400 W/ m2 for about 8 hours per day. The current generated by the solar panel is roughly proportional to the ratio of the actual solar radiation to 1000 W/ m2 multiplied by 600 mA. Therefore, the average current would be (400/1000)*600 = 240 mA.
Amp-Hours is equal to the average current multiplied by the number of hours at this current. For this example the worst case would be (240 mA) * (8 hours) = 1920 mAmp-Hours = 1.92 Amp-Hours.
Rather than searching historical records, you can create your own historical solar radiation database using a weather station equipped with a solar radiation sensor. You can then estimate panel output as outlined above after solar panel installation of course.