To calculate the change in temperature, subtract the initial temperature from the final temperature. Example: 84.2 degree Fahrenheit - 41 degrees Fahrenheit = 43.2 degrees Fahrenheit. The temperature from morning to afternoon changed by 43.2 degrees Fahrenheit.
It needs 12 volts so it will be the standard modern power supply provides 12 volts of power.
Here's a basic description of how the electric power gets to your house. Most homes are supplied with a 220 volt service capable of about 200 amps. Some older homes might not be wired that way. They may just have a 110 volt service.