The answer to 'what size outlet do I need' is that the size of the electrical outlet you need depends on the voltage, amperage, and specific requirements of the device or appliance you are powering. Most standard household outlets in the United States are 120-volt, 15-amp or 20-amp outlets. These are the most common sizes used for general household purposes like powering lamps, electronics, and small appliances.
If you have a larger appliance or device that requires more power, you may need a 240-volt outlet, which is commonly used for electric ovens, dryers, air conditioners, and other high-power equipment. The size of the outlet must match the power requirements of the device to ensure safe and proper operation.