How Much Grid Power Does a DC Fast Charging Site Need?

Short answer: add up the input power of all chargers (output ÷ efficiency of about 0.95, plus auxiliaries), then apply a diversity factor for the chance that they will not all run at full output together. Four 120 kW chargers need about 500 kW at full load. Most utilities want a dedicated transformer from about 200–300 kW upward, and the grid application is often the longest step of the project.

Step 1: Input power per charger

Charger output	Approx. grid input at full output	Approx. current at 400 V
30 kW	32 kW	46 A
60 kW	63 kW	91 A
120 kW	126 kW	182 A
240 kW	253 kW	365 A
360 kW	380 kW	548 A

These are planning numbers: efficiency is around 94–96% for modern power modules, and standby and cooling add a little. Ask the supplier for the exact input current of the model.

Step 2: Site total and diversity

Site	Nameplate sum	Realistic site limit
2 × 60 kW	126 kW	126 kW (small site; run both fully)
4 × 120 kW	504 kW	400–500 kW
8 × 180 kW	1,500 kW	1,000–1,300 kW
12 × 360 kW	4,500 kW	2,500–3,500 kW

Power sharing on floor-standing dual-connector chargers and site-level power management allow a site limit below the nameplate sum. The right factor depends on traffic: highway sites at holiday peaks run close to the sum; city sites usually run well below it. Ask the utility if it accepts a managed connection (a contract limit enforced by the charger controller).

Step 3: Connection level

Site load	Typical connection	Notes
Up to ~100–150 kW	Existing low-voltage supply, possibly upgraded	Check the main fuse and cable
~150–1,000 kW	Dedicated transformer on low-voltage side	Pad-mounted transformer, switchgear
Above ~1 MW	Medium-voltage connection	Longer lead time; customer substation

Rules and thresholds vary by country and utility.

Step 4: The utility process

1. Pre-application: location, load, schedule.
2. Capacity study: the utility checks the local network.
3. Offer: costs, works, timeline, and your contribution.
4. Works: trenching, transformer, metering.
5. Energisation: inspection and commissioning.

This process can take from a few months to over a year. Start early and send complete information, including the charging profile (not just the nameplate).

Reducing the connection size

• Power sharing and a site limit — managed by the charger controller. See dynamic load management.
• Battery storage — a battery handles peaks and recharges from a smaller connection. Compare with the upgrade fee; the answer depends on tariff and utilisation.
• On-site solar — reduces energy cost more than peak demand.
• Time-of-use limits — lower the site limit at expensive hours.

Demand charges and the business case

The size of the connection also decides the fixed monthly fees in many tariffs, and demand charges punish peaks. For the economics see demand charges and the cost structure of a charging station.

Practical checklist

Item	Question
Input current	Which current per charger, at what power factor?
Harmonics	Total harmonic distortion limit set by the utility?
Cable and distance	Distance from transformer to chargers — see wire size
Protection	Short-circuit rating of switchgear; surge protection
Space	Transformer pad, clearances, access for trucks
Civil	Foundations and trenches — see DC charger installation

VULTAE DC chargers

VULTAE DC chargers range from 20 kW wall-mounted to 360 kW floor-standing with dual connectors and dynamic power sharing; power on the floor-standing series can be expanded from 60 kW to 300 kW. Send us the model and the utility’s questions, and we will provide the input current and other electrical data for the exact model for your utility application. See the DC fast charger and the compact DC charger.