The thermal power of the sun will heat the panel, to the extent that it is not reflected. But no electrical power (or any power) is being "generated" by the panel, the panel is just absorbing photons like anything else with low albedo.
That's just nitpicking. There is thermal power generated from the electromagnetic power from the sun and GP is right that a solar panel turned off will be hotter than one turned on.
And if that was the original poster's intent, I apologize for nitpicking. My impression was that the use of "generating power" in the given (open circuit) context suggested a fundamental misunderstanding of the behavior of solar cells in this situation on behalf of the poster, and thought I might clarify; and perhaps even if the original poster understood this already, someone else learned something.
