PV Gap

Mathew Said:

how many volts does a 2 inch by 2 1/2 inch solar panel take?

We Answered:

That depends on the solar panel. All solar panels have a watt-peak rating, effectively the maximum amount of power they produce under standard conditions (25 Celsius, solar radiation through airmass of 1.5, and 1 kW/m^2 of solar energy).

While you're looking at solar panels, keep in mind that you will generally see power generation that is much lower than the watt-peak.