When selecting an emergency backup generator for a commercial building, there are several crucial factors to consider: 1. Power output: The generator should have enough power output to keep essential systems running during an outage. This will depend on the size of the building and the equipment that needs to be powered. 2. Fuel type: The generator should be able to run on the fuel type that is readily available and easy to obtain in case of an emergency. 3. Size and location: The generator should be able to fit in the designated location and be easy to access for maintenance. 4. Reliability: The generator should have a proven track record of reliability and be from a reputable manufacturer. 5. Maintenance: The generator should be easy to maintain and have a comprehensive maintenance plan. 6. Noise level: The generator should have a low noise level to minimize disturbance to the surrounding. 7. Safety features: The generator should have the necessary safety features to protect both the building and the generator operators. It is important to consult with a professional to find the best generator that fits your need, budget and that comply with local regulations and codes.