Connections

You can connect Facilities. When connected they form a Grid and share energy, this is valid for all types of connections.

How to connect
You start at one facility and begin building connection. Then you walk to the other end and finish the connection. You need to have enough cable in inventory when finishing the connection.

You can only build new cable connections, and then later upgrade them to other types.

Cable
May be built between any type of facility

Conveyor belt
You can upgrade existing cable connection between mines and factories or factories and factories where the output of one facility matches the input of the other facility.

You need to have one engine and enough conveyor belt inventory to upgrade the connection.

High Capacity Cable
May only be build between end game facilities.

You need to have enough High Capacity Cable in inventory to upgrade the connection.

Please don't visit until you have finished the late game mission to collect knowledge to avoid spoilers.

Grids
Connected facilities form grids. They share energy storage and usage. Material may only be moved from a facility to another using conveyor belt though.

A grid may be underpowered. Then it will use existing energy until it runs out and then only accordining that much time as it has energy.