Seems that ~100W is regularly quoted as the average human energy output, so that'd be something like 18 MWh for 20 years (assuming 100% efficiency of food input). I suppose there's also the energy cost of all the training infrastructure (daycare, school teachers, homes, transportation, etc.), and also all the energy consumption of all humans that have come before and built those cities and knowledge infrastructure (although LLMs sit atop that anyway), and then the millions (billions?) of generations of creatures going back to the earliest organisms, who have been optimising how cells work to lower their energy cost.
For that setup cost, you get a single-threaded human, starting to specialise in a single field. They will work in that field for around 7.5 hours every weekday, with ~20 days of holiday a year, for around 45 years, and then retire.
Llama v2 70B cost 1,720,320 GPU-hours[1] at 400W, so 688MWh. Once trained, it can be run 24/7, and you can spin up as many instances as you want on much lower spec hardware. That model produces output faster than a human while consuming around ~30W on my Macbook Pro.
Now, I know we're in pretty shaky spherical cow territory here, comparing a human (albeit a highly educated one) to Llama v2 in logical reasoning... but consider that this is the state of the art in generally-available LLMs after a few decades of research into machine learning & we're using repurposed silicon to compute vs the amazing complexity and physics-leveraging approach of human neurons... and the training cost is only 1 order of magnitude off humans.
Again, I'm not disagreeing with the general point of the OP, I'm not saying that the models we're using right now are the best/right ones (or that the hardware they're running on are the most efficient way of executing them), but I don't think the energy efficiency gap is actually all that high considering
Edit: If you look at the total footprint (considering not just the efficiency of the neurons, but the whole animal) the figures are very close - the llama model card indicates that v2 70B caused the emission of ~300T of CO2, and an average human in the US emits 16T of CO2 a year, so a human would emit ~320T of CO2 in 20 years. I assume children don't have as high a CO2 output, but even so it seems like it's the same order of magnitude.
1: https://github.com/facebookresearch/llama/blob/main/MODEL_CA...