Keep in mind Hashgraph and Blockchain are very different, in that Hadera is a permissioned network with public access (each round has a known number of nodes that must participate to exit the round).

What do you mean by round?

"What do you mean by round?"

Because Hashgraph is BFT, a round is a round of voting for confirmation. Its done virtually but you have to have 2/3rds of nodes agree on the state to close a round and have a confirmed state. To have 2/3rds you have to have a fixed and known number of nodes in the round. See BFT for more information.

The point I was trying to make, is that they are very different in benefits and limitations.

Bitcoin's electricity use isn't due to transaction volume, it's due to mining. A 1kb block takes about the same amount of energy to produce as a 1MB block.

Doesn't Bitcoin need mining to handle transactions?

Yes, is does. However, the amount of electricity used isn't directly correlated with the number of transactions on the network. It instead follows the number of miners validating those transactions. A empty block validating no transaction takes more or less the same amount of work as a full block to mine. That was GP's point, I think.

That being said, having a lot of transactions going around is probably correlated with Bitcoin getting more popular, which is again probably correlated with more miners coming in, which would indeed lead to higher energy consumption. That's an indirect effect, however.