This isn't official, but I looked into this, and this was the most reasonable conclusion I could make:
The Equation for Power Output f(x) with Power Level x is:
f(x) = 0.25x^2 * (x+1)^2
f(x) = The Power Output in PLU
x = The Power Level
To find the value of 1 PLU (Power Level Unit), we can use the fact that Freeza destroyed Namek, and if we assume Namek's binding energy is the same as Earth's, we get about 224 x 10^30 Joules. Freeza powered up for 6813 to 6846 frames, and since the framerate is 30 fps, the time is anywhere from 227.1 seconds to 228.2 seconds. Based on the equation presented, a power level of 60,000,000 comes to 3.24 x 10^30. This means the value of 1 Power Level Unit is 12357457/40659859 Watts, or about 0.304 Watts.
This equation makes the farmer's power level of 5 equal to 68.4 Watts, and also gives the following Power Levels:
GE90 Jet Engine = 177
Space Shuttle = 626
Saturn V Rocket = 1,215
Strongest Laser Ever Built (ELI) = 40,276
The Sun = 8,420,000
Keep in mind that these do not increase linearly, so 50% of a power level of 100 is not 50, its about 84.
Also, I found Mr. Satan's Power Level:
Mr. Satan pulls buses in the cell saga. In my research, I found a similar bus with a mass 12000 kg and a length of 772 cm. There are 4 buses, so he pulled a mass of 48000 kg a distance of 3088 cm. He did this in 1129 frames, or about 37.6 seconds, and as the total work done is 14,535,808.896 Joules, the average power was about 387 kW. This puts Mr. Satan's power level at 43.
Calculator Used: https://web2.0calc.com/
Episode 97, in which Freeza destroys Namek