What if there is hardly any sunshine for several days?
Different geographic regions provide various amounts of daily sunshine. It is recommended that an off grid system has enough battery power to account for five days of inclement weather. The American southwest averages 5 sunshine hours per day and the northeast receives about 3 hours of daily sunshine. More solar panels will increase the amount of power generated when the sun is shining. A solar generating system with batteries supplies electricity when it is needed. The amount of electricity that can be used after sunset or on cloudy days is determined by the output of the solar energy modules and the storage capacity of the battery bank. Including more modules and batteries increases system cost, so energy requirements (both in terms of peak loads and the average duration of the loads) are carefully studied to determine optimum system size. A well-designed system balances cost and convenience to meet the needs of the particular application, and can be expanded if those needs change.
