Yes, you can monitor consumption only. CTs can be used to monitor whole site consumption or sub-circuits, according to the requirements of the customer. However, such sites do not have a 'Performance' page because there is no solar production being monitored.
Also, if only sub-circuit consumption is being monitored, there will be no Live Monitor feature (5 second interval data) available on the customer dashboard. To activate the Live Monitor, at least one channel should be allocated to whole site consumption (AC Load Net).