What a good question. It's all going to depend on how cleverly they've designed their EMC filtering, and I wouldn't be surprised if it varies hugely between different models. So unfortunately even if someone else measures their Mac you'll need to check it's the same model.


IF you can get hold of a PAT tester with leakage current readout that's going to be the surest way to find out - but I'm sure you'd already thought of that!


On the following thread people were discussing leakage of 3.5mA for desktop PCs a few years ago, but I wouldn't be surprised if modern Macs used lower leakage filters than that. https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=29903  I believe 3.5mA is still the maximum allowed leakage current limit for desktop computers under IEC 60950-1, but commercial filters are often now below 1mA. 


But I wouldn't expect it to be much below 1mA (unless they've been VERY clever), so you might find yourself borderline.


I'll be interested to know what you find out...


Cheers,


Andy

Also be aware that the waveform of the current to earth will have  50Hz component that will be less than the 3mA, as noted probably quite a bit less, but will also have high frequency spikes at the switching frequency, so ~ 100s of kHz, that have a peak amplitude far higher, but are of such short duration as to be safely ignored. But cause confusion if you use a scope and a current probe to make the measurement.

A flick of the meter on the capacitance range between L and E pins of the plug will give you a first guess as to the filter structure. At 230V and 50Hz, given that 10nF is about 300 k j ohms, you can allow for a touch under a milliamp per 10nanofarads.