To ensure that your generator is NEC-compliant, you must hire a certified electrician who can inspect your facility and determine your power usage and generator needs. The electrician will ensure that the generator is compliant with National Electrical Code (NEC) requirements, including sizing, use, installation, and safety features. If you choose to determine the generator size yourself, you must be willing to perform a series of mathematical calculations to determine the correct size and ensure that it is NEC-compliant.