Stop 02 of 09 · Planning

Why does the grid connection decide so much?

About 7 min · 3 questions ·

Thursdaymonth 2
The situation

A meeting with the grid operator. The retail park's existing connection has 250 kVA, enough for lighting, shops and a few AC charge points.

The hub would need about 1.2 MW on top.

The questionWhy does the connection decide what the hub can be, and when it can open?

Current at 400 volts, three phasesWhy size changes the connection
One AC point, 22 kW32A

a tenth of the retail park's 250 kVA, about 360 A

One DC charger, 300 kW433A

more than the retail park's whole connection

The hub, 1.2 MW1,732A

at low voltage, a thick bundle of cables

The hub at 20 kV35A

the same power at medium voltage

Computed: current equals power divided by √3 times voltage. At 20,000 volts, the same power needs one fiftieth of the current.

Two ways to connectLow voltage or medium voltage
Low voltageHere: the retail park's existing 250 kVA, shared with the shops.
  1. Street grid400 V
  2. Connectionshared with the building
  3. Chargersa few hundred kW at most
Medium voltageHere: 1.2 MW for the hub, with a transformer of its own.
  1. Medium-voltage line10 to 30 kV in Germany
  2. Own transformeron site
  3. Switchgearprotection and metering
  4. Chargersmegawatts possible

Which voltage level a site needs is for the grid operator to decide; levels and limits differ by country and grid operator.

What the grid operator does

The checks whether its grid can carry the new load, offers a connection and builds its part. EU law requires Member States to make connecting charge points easier and requires grid operators to cooperate on a non-discriminatory basis with any company that builds or runs them.

Grid operators themselves may, in principle, not own or operate public charge points. Their job is the connection, not the charging.

Time and size

  • Time. A new connection needs planning, a transformer and often cable works in the street. In this project, the offer gives about six months from signing to energisation (deep dive of this path).
  • Size. The connection sets the ceiling for the hub's total power. A larger connection costs more, a smaller one limits the hub.
  • Sharing. With , the chargers share a connection that is smaller than the sum of their ratings, the subject of its own path.

Check your understanding

3 questions. Answer all of them to complete this stop. Each answer explains itself.

01Question 1 of 3

Why does this hub connect at medium voltage?

02Question 2 of 3

What does EU law require of grid operators towards charging companies?

03Question 3 of 3

How can load management help with the grid connection?

Further in other paths

  1. Energy and grid integration · Stop 01How does electricity reach a charger?From the power station to the wallbox: the grid levels electricity passes through, and where charging connects to them.
  2. Load management · Stop 01Why can't every car charge at full power?Twenty charge points of 11 kW, but only 80 kW for charging: why connections are smaller than the sum of the chargers, and why that rarely matters.
  1. EUR-Lex: Directive (EU) 2019/944 on common rules for the internal market for electricity, Article 33. https://eur-lex.europa.eu/eli/dir/2019/944/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.
  2. EUR-Lex: Directive (EU) 2019/944 on common rules for the internal market for electricity, Article 33. https://eur-lex.europa.eu/eli/dir/2019/944/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.
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