A retail plaza owner in Novi signed off on installing six Level 2 electric vehicle (EV) chargers in the parking lot without ever calling the company that services the building’s rooftop units. Three weeks after the chargers went live, the anchor tenant’s rooftop unit started tripping its breaker on the hottest afternoons of the month. The chargers hadn’t damaged anything. They had simply used up electrical capacity the HVAC system depended on, and nobody had run the numbers before the work began.

Why EV Chargers and HVAC Equipment Are Suddenly Competing

A commercial Level 2 EV charger typically draws somewhere between 30 and 80 amps depending on the model, according to commercial charging equipment manufacturer BTC Power. Under National Electrical Code (NEC) Article 625, EV charging equipment is treated as a continuous load, and per NEC 625.41, the circuit has to be sized at 125 percent of the charger’s rated amperage. Six chargers at even a modest 30 amps each can add well over 200 amps of demand once that continuous-load multiplier is applied. That is not a small addition to a panel that was sized decades ago around a building’s original mechanical and lighting loads. There was little room built in for anything new.

What Happened at the Novi Plaza

The building’s electrical panel had enough physical breaker space for the new circuits, which is what the electrician who installed the chargers checked. Physical space is not the same as available capacity. Nobody calculated the building’s actual peak demand against the panel’s rated capacity before adding the new continuous load, and the rooftop unit, an older system already drawing close to its full rated amperage on the hottest days, started tripping once the chargers were pulling power at the same time the cooling system needed it most.

Why a Load Calculation Has to Happen Before the Chargers Do

A proper load calculation looks at a building’s actual historical peak electrical demand, not its theoretical panel rating, and compares that against what the new equipment will add. This is the same calculation an electrician should already be running before any major addition. EV charger installations are often handled by a contractor with no visibility into what else shares that panel. HVAC equipment is the biggest blind spot. It only pulls its full rated amperage on the hottest or coldest days of the year, the exact moment a load conflict tends to show up.

What to Ask Before You Add Chargers

If your building is adding EV charging, get a load calculation that includes your HVAC equipment’s actual peak draw, not just its nameplate rating, before the chargers go in. Ask whether the charging stations will use load management technology that can automatically reduce charging speed during periods of high building demand. Many commercial charger systems offer this as a built-in option, and it can eliminate the conflict entirely without requiring a full panel upgrade. And if your panel is already running close to capacity, budget for the panel upgrade as part of the charging project rather than discovering the shortfall after the first hot week of summer.

Why This Problem Is Only Getting More Common

A single charger rarely causes a noticeable conflict on its own. The trouble shows up with multi-charger installations, six chargers landing on a panel in one project instead of one charger added at a time. That’s how a landlord satisfying a single tenant request or a new leasing requirement ends up adding the full continuous load all at once, with no phased rollout to absorb it gradually.

Load Management Is Often Cheaper Than a Panel Upgrade

A full electrical service upgrade to a commercial building typically runs from $5,000 to $30,000 or more, according to cost data compiled by electrical contractors. That range covers permitting and utility coordination up front, plus the physical panel work itself. Load management systems that throttle charger output during peak building demand periods, then restore full charging speed overnight when HVAC load drops off, frequently cost a fraction of that and solve the same underlying capacity conflict. The tradeoff is slightly slower charging during the building’s peak hours.

The Novi plaza didn’t need a full service upgrade. The property manager installed a load management system for $4,100, tied to the same panel that was tripping the rooftop unit’s breaker. It throttles the six chargers back automatically on afternoons when the cooling system is drawing its full load, then lets them charge at full speed once the sun goes down and the RTU backs off. The panel upgrade quote it replaced ran $23,000. The breaker hasn’t tripped since.

Sources

National Fire Protection Association: NEC Article 625, Electric Vehicle Power Transfer Systems

BTC Power: AC Chargers, Level 2 (Commercial Charger Amperage Specifications)

Caudill’s: Electrical Panel Upgrade Cost Guide (Full Service Upgrade Cost Range)