Your electrician should bring a 230v 10a power supply to one side of the entrance to power your electric gates. The size of the power cable will depend upon the length of the cable run.
For example a 20 mtr cable run would require a 3 core 2.5mm core cable and a 50 mtr cable run would require a 3 core 4.0mm core cable. Outdoor power should be run in SWA (Steel Wire Armoured) cable.
You may select hard wired controls to operate your gates that require control cables between the house and the gates. If you are trenching for a power cable it could be wise to also lay a pair of screened CAT 5 cables between the house and the entrance. This will be ample for a majority of audio intercom and video intercom systems and the cable cost is minimal.
A majority of intercoms systems now fitted to automatic gates are wireless. This means there are no cables to run around to the intercom handsets inside the house (and no disturbance to decoration) as well as no cable running outside to the entrance. Your specialist electric gate installer should be able to quote for laying in the power if required.