When selecting a flywheel generator, you must prioritize Energy Storage Capacity (kWh) and Power Rating (kW) to ensure it meets your load requirements. Pay close attention to the Rotational Speed (RPM)—high-speed flywheels (up to 50,000 RPM) typically use carbon-fiber composites, while low-speed versions use steel. Ensure the unit features Magnetic Levitation (Maglev) bearings or high-grade ceramic bearings to minimize friction and extend the operational lifespan, which should ideally exceed 20 years or 100,000+ charge/discharge cycles.