Site power checker: how many EV chargers can my supply run?

Your supply size and your current peak demand set how many chargers you can add before you need a grid upgrade. Use the main fuse rating per phase and your highest demand from a half-hourly bill or meter.

How this is worked out

Capacity is 230 V × amps × phases, treated as kW (power factor 1).
Spare capacity is the supply less your current peak demand. Installers usually keep a margin on top.
Without load management every charger must be able to run at full power at once.
11 kW and 22 kW chargers need a three-phase supply; on single phase, choose 7.4 kW or below.
With dynamic load management chargers share the spare capacity. Under IEC 61851 a charger cannot charge below 6 A per phase, which sets the most chargers that can run at once.
A survey and the network operator decide the real figure; this is a first check, not a design.