Commercial Generator Sizing for Businesses
Power outages cost businesses real money. Lost revenue, spoiled inventory, data loss, employee downtime, and customer disruption add up fast. For many businesses, a single extended outage can result in losses that exceed the cost of a commercial generator. Sizing that generator correctly is critical: too small and the system fails under load, too large and you overspend on capacity you never use. Here is how to determine the right commercial generator size for your facility.
Why Commercial Sizing Is Different
Commercial generator sizing is more complex than residential because business electrical loads are larger, more varied, and often include three-phase power requirements. Commercial buildings may have multiple HVAC rooftop units, commercial refrigeration, server rooms, industrial lighting, elevators, fire suppression pump systems, and specialized equipment. Each of these loads has specific running and starting requirements that must be accounted for in the generator specification.
General Sizing by Business Type
Small Retail and Office (25kW to 60kW)
A small retail store, professional office, or restaurant under 3,000 square feet typically requires 25kW to 60kW depending on HVAC size, refrigeration needs, and equipment load. A dental office with digital imaging equipment, a small restaurant with commercial coolers and cooking equipment, or a retail store with point-of-sale systems and security all fall in this range.
Mid-Size Facilities (60kW to 150kW)
Larger retail spaces, multi-suite office buildings, medium restaurants, grocery stores, medical clinics, and small manufacturing operations typically need 60kW to 150kW. These facilities often have multiple HVAC zones, significant lighting loads, and business-critical equipment that must remain operational during outages.
Large Commercial Operations (150kW to 500kW+)
Large office buildings, hospitals, data centers, hotels, large manufacturing plants, and multi-story retail require 150kW to 500kW or more. These installations often involve multiple generator units in parallel configurations to provide redundancy and scalable capacity.
Three-Phase Power
Most commercial buildings operate on three-phase electrical service, which is more efficient for large loads and commercial HVAC systems. Commercial generators are available in both single-phase and three-phase configurations. If your facility has three-phase service, your generator must also be three-phase. Verify your service type with your electrician before specifying a generator.
The Professional Load Study
For commercial applications, a professional load study is not optional. A qualified electrical engineer or generator sizing specialist will inventory every electrical load in your facility, identify which loads are critical (must run during an outage) versus non-critical, calculate total running load and peak demand including motor starting surges, account for future expansion, and specify the correct generator size, fuel type, and transfer switch configuration. This study ensures the generator is sized accurately and prevents costly over or under sizing.
Commercial Generator Brands
IB Lighting supplies commercial generators from Generac, Kohler, and Cummins. All three manufacturers offer robust commercial product lines with units ranging from 22kW to over 500kW. Generac’s Protector series is popular for light commercial applications. Kohler and Cummins both have deep commercial and industrial heritage with units designed for continuous-duty and mission-critical applications.
For commercial generator inquiries, call IB Lighting at (800) 674-9019. Our team can help you identify the right equipment, provide competitive pricing, and coordinate delivery to your facility. We also work with electrical contractors on project specifications and multi-unit orders.