It’s hard to know for sure, but we can make some estimates. If there are 500 HoloPorts running at less than 1/10 capacity with a 45 watt power supply (which draw between 10 to 32 watts depending on load) then that comes out to around 11 kWh for every hour the network is running. Compare that to 2.1 million kWh per hour for the Ethereum network or 656 kWh for a single bitcoin transaction!
At the moment each host running a HoloPort is paying their own electricity, but keep in mind that it’s like having a 25 watt light bulb turned on. It’s a little early to make serious bandwidth estimates, and they vary hugely based on usage load and creation of new content. Since chat messages are small, overall bandwidth per node is quite small just like energy consumption is low.