Not sure about that one; TDP isn't exactly the same as actual power consumption, but for i9-12900K it is more than doubled.

You're comparing the 8700K TDP to the 12900K maximum turbo power (which you can only "achieve" when using all cores fully). In "normal" usage 12th gen is very energy efficient and perform (unsurprisingly) much better than AMD Zen 2/3 SKUs.

“Normal” usage isn’t going to be terribly more energy efficient - efficiency doesn’t change much depending on number of cores loaded. (Unless you’re only loading efficiency cores in the case of 12th-gen Intel.) (More cores might actually be more efficient if it thermally limits the CPU - in that case the frequency will be throttled, which will put you at a more efficient place on the voltage curve.)

Tom’s Hardware 5800X3D review[1] has some efficiency numbers if you scroll down. High-end Zen 3 chips seem mostly a bit more efficient than high-end 12th-gen Intel. By far the most efficient CPU tested is the 5700X, which is AMD’s fastest 65W TDP part. They don’t have any low-power Intel chips (e.g. Core i7-12700T) in the test. (Though I’ve always found retail availability of low-power Intel chips to be terrible.)

1. https://www.tomshardware.com/news/amd-ryzen-7-5800x3d-review

If you are referring to the all-core Handbrake efficiency graph then I'm not sure what's to complain about. The 12th-gen top-end SKUs perform far better while being roughly as efficient as the slower AMD parts, which is a clear win in my book. The 5700X performing well here is not surprising, as it's heavily restricted by the low TDP so in this all-core workload it might even remain under 4 GHz, also resulting in the lowest performance by far.

The situation is very different for lightly threaded loads (e.g. what PCs tend to do a lot of the time, this also includes most games).

For Handbrake the 12700K performs about 12% faster than the 5900X while being about 13% less efficient - I don’t think “perform far better while being roughly as efficient” is a fair characterization there - it performs better by about the same amount as it’s less efficient.

And the 5700X having low performance is taken into account by efficiency metrics - efficiency is performance divided by power draw, so whatever it in performance it more than gains in reduced power draw. (Of course, you might value your time more than your electric bill.)

I watched GamersNexus' 5800X3D review a few days ago, and the thing that stood out to me was their direct measurement of power draw on the 12V rail; it included a 120W result for the 5950X, and 240W (!) for the 12900KS. These parts are pretty comparable for the workloads I care about (compilation, mostly) but Intel's best part does the same job in roughly the same amount of time, for more money and twice the power draw. Is there something I'm missing, before I just buy the AMD for an upgrade?

You appear to be correct. I dug around a bit, and on Intel's ARK there are 2 numbers: Processor Base Power (125W) and Maximum Turbo Power (241W, same as the one used with the benchmarks). It appears the Processor Base Power might be a closer equivalent to TDP than the other one. If that's the case, the 12900K is much more efficient than the 8700K.

Can't edit the comment anymore, but I made a mistake. The Maximum Turbo Power explanation is as follows: "The maximum sustained (>1s) power dissipation of the processor as limited by current and/or temperature controls."

Somehow I have misread it to mean that it can peak up to said power limit for UNDER 1 second, which is incorrect - the CPU will run at that limit for as long as cooling allows. The CPU will gulp down ~240W when under full load, as evidenced here at ~24 minutes: https://www.youtube.com/watch?v=fhI9tLOg-6I