Commercial & Industrial Electrical

Three-Phase Power Explained for Building Owners

Three-phase power delivers more capacity efficiently, which is why most commercial buildings use it.

Updated 2026-10-15

Common commercial voltages

In the U.S.:

208Y/120V: offices, retail, restaurants — runs both 120V loads and 208V equipment
480Y/277V: larger buildings, warehouses, industrial — 277V lighting and 480V motors, with transformers for 120V
120/240V single-phase: small commercial spaces and homes

When a business needs three-phase

Large HVAC, commercial kitchen equipment, motors, compressors, welders, and DC fast EV chargers commonly require three-phase. Running large motors on three-phase is more efficient and smoother.

Adding or upgrading service

Bringing three-phase to a site that lacks it can be expensive and depends on utility infrastructure nearby. Engage the utility early with a load letter from your engineer or contractor.

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Frequently asked questions

Can I use phase converters instead?

Phase converters can run some three-phase equipment from single-phase service but have efficiency and capacity limits. They're a stopgap for small loads.

Why do lights flicker when motors start?

Voltage drop on starting current. Soft starters, VFDs, or circuit changes can help.

How long does a utility service upgrade take?

From weeks to many months, depending on transformer availability and utility workload.

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This guide is general information, not engineering or legal advice. Electrical codes are adopted and amended locally — consult a licensed electrician and your local building department for your project.