It's an "estimate" but if the mining operations of these 137 miners have known addresses (which I assume they have to for compliance), it's going to be accurate

It's an "estimate" but if the mining operations of these 137 miners have known addresses (which I assume they have to for compliance), it's going to be accurate within 20%. The block reward is irrelevant, we just need to look at the hashrate of the network Basically, take the overall hashrate of the entire network which is determined from the block difficulty (this fluctuates and was likely higher when bitcoin was more valuable, though not necessarily), and assume all blocks are mined by operators running state of the art mining hardware (realistically 90-98% of blocks will be mined by people running hardware that's 80-100% of the maximum possible efficiency, and any miners running worse hardware will be consuming more energy, but we can pretend they're all on the best hardware) Using that, you can get the overall hashrate of the network. Once you have that, you can take the percentage of blocks mined by these 137 miners in a year. Again, be generous and assume they're all running state of the art hardware. If 10% of all blocks are mined by these 137 mining ops, guess what, they're using 10% of the total energy being inhaled by the network.