Power assessment: can your building handle EV chargers?

Why a power assessment is the first step

A charger is one of the largest loads in a building: a single 11 kW point draws as much as several apartments at peak. Connecting chargers by guesswork risks tripping protective devices, overheating cables and, in extreme cases, a power cut for the entire building.

A power assessment answers three questions: how much power the building has available, how much it actually uses and how much is left for charging. On that basis, the installation assessment and charger installation design are prepared.

Connection capacity, contracted capacity and actual load

• Connection capacity — the maximum power the grid operator provides to the building. It results from the connection conditions and the agreement with the operator.
• Contracted capacity — the power ordered in the distribution agreement, shown on the invoice. It may be lower than the connection capacity; raising it within those limits is usually simpler than upgrading the connection.
• Actual load — how much power the building really draws, including at peak (lifts, lighting, garage ventilation, pumps). Only the difference between the available power and the peak, minus a safety margin, is the spare capacity for EV charging.

What we check during the assessment

• Documents: connection conditions, distribution agreement, invoices and the electrical installation design, if available.
• Load measurements: we log power consumption over time to establish the real peak and how consumption changes at night, when cars most often charge.
• Switchboards and protective devices: technical condition, free space for new circuits, protection ratings and their selectivity.
• Supply lines and cables: cross-sections, route lengths and the possibility of running power to the garage or car park.
• Garage supply: whether the garage has its own meter and supply or uses the building’s common-area installation.
• Protection requirements: including residual current protection suitable for chargers and fire protection conditions in the garage.

What if installation documentation is missing

Older buildings often lack complete electrical documentation, or it does not reflect the actual state. This does not block the project. We reconstruct the data from an on-site survey, measurements and calculations, and then prepare an overview diagram of the installation, which becomes the basis for the assessment and design.

Example: how many chargers fit in an apartment block

A building has a connection capacity of 80 kW, and measurements show a peak of 45 kW in the evening and approx. 20 kW at night. After deducting a safety margin, approx. 25 kW is left in the evening, and much more at night.

Without load management, only two 11 kW chargers would fit here, because each needs its full power reserved. With dynamic load balancing (DLB), the same building can serve a dozen or more points: the system shares the available power among the cars that are charging and limits it in the evening, when the apartments’ consumption rises. At night, when cars are parked longest, they charge at higher power.

Illustrative example. The actual spare capacity and number of points result from the measurements and assessment of the specific building.

When spare capacity is limited

Limited spare capacity does not mean chargers cannot be installed. Before the housing community decides on an expensive connection upgrade, it is worth checking cheaper options:

• Dynamic load management — chargers share the available power instead of reserving it rigidly; this is usually the cheapest solution.
• Power limits for a group of chargers, and charging mainly at night, when the building uses the least energy.
• Raising the contracted capacity within the connection capacity — usually only requires amending the agreement with the operator.
• Increasing the connection capacity or a separate connection for the garage — when the planned number of points is large; this is a procedure with the grid operator that takes time and money, so it is worth planning within a single collective design.
• Phased expansion — the installation is designed for the target number of points, and chargers are added as needed.

Power assessment as part of the installation assessment and design

At Domena Power, the power assessment is part of the charging installation assessment and design. The complete documentation package costs 3,000 zł net (3,690 zł gross) for the first point and 330 zł net (405.90 zł gross) for each additional one in the same property. After the rollout, the Domena Power system keeps power limits in check, manages the load dynamically and shows charging peaks in the panel.