Measure the open circuit voltage of the photovoltaic panel

Read the voltage on your multimeter and compare it to the open circuit voltage (Voc) listed on the back of your panel. If your voltage reading is negative, reverse the probes and measure again. [pdf]

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]

Photovoltaic panel shade current and voltage

When a solar panel is equally shaded, the amount of light it is receiving is very low. This does not always reflect on its voltage, but it directly affects the current.. When a solar panel is equally shaded, the amount of light it is receiving is very low. This does not always reflect on its voltage, but it directly affects the current.. The shaded spot on one panel will decrease the string of panels to 3 amps at 52.5 volts. [pdf]