How much tilt should photovoltaic panels have to be to be effective

To optimize performance, tilt your panels at an angle that is 10-15 degrees less than your latitude. For example, if you live at a latitude of 40 degrees, set your panels at about 25-30 degrees. [pdf]

Solar energy working Mexico

Solar power in Mexico has the potential to produce vast amounts of energy. 70% of the country has an of greater than 4.5 kWh/m /day. Using 15% efficient , a square 25 km (16 mi) on each side in the state of or the (0.01% of Mexico) could supply all of Mexico's electricity. [pdf]