Bitcoin energy consumption is not a function of the number of transactions. A node broadcasts a transaction which miners then include in a block which, within limits, can have an arbitrary number of transactions. It is the Proof of Work(PoW) contest to find a valid hash for the block at a certain level of difficulty that creates a valid block.
Further, with Layer 2 solutions, a single transaction in a Bitcoin block can be "dense" with the value of an arbitrary number of transactions that occurred in Layer 2. That is Bitcoin providing the settlement layer.
Importantly, because Bitcoin is a timechain where the current blockheight represents the entire history of Bitcoin.
"The average cost per transaction isn’t an adequate metric for measuring the efficiency of Bitcoin’s PoW, it should be defined in terms of the security of an economic history. The energy spend secures the stock of bitcoin, and that percentage is going down over time as inflation decreases. A Bitcoin “accumulates” the energy associated with all the blocks mined since its creation. LaurentMT, a researcher, has found empirically that Bitcoin’s PoW is indeed becoming more efficient over time: increasing cost is counterbalanced by the even greater increasing total value secured by the system."[0]
[0] : https://danhedl.medium.com/pow-is-efficient-aa3d442754d3