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.
The power coming to your home is typically 220 volts and then the wiring in the breaker panel delivers 110 volts to your outlets and various electrical fixtures and the full 220 volts to high demand devices like your water heater and electric range.