What size of 12v transformer will run 500watts?

To run a 500-watt load with a 12V transformer, you need to calculate the current required using the formula: Current (Amps) = Power (Watts) / Voltage (Volts). For 500 watts at 12 volts, that would be approximately 41.67 amps (500W / 12V). Therefore, you should select a transformer rated for at least 500 watts, but it's advisable to choose one with a higher capacity (e.g., 600-700 watts) to ensure it can handle the load safely and accommodate any inrush currents.