portable air conditioners: efficiency compared to fixed systems?

These are the sort of things people buy their pensioner parents in the middle of summer, as a cheap solution to cooling a room
Unfortunately, they suffer from some heat leakage. I have seen a claim that you can reduce this by insulating the flexible duct that goes out the window, but that is not the complete answer. I have looked at some in shops, and if you feel around it, you can always find a warm corner or two on it. So I wonder about the ratio of (cooler power)/(electric power in) how does this typically compare to a (fixed) split-system?
I know there exist some portable split systems - delonghi and one of the Jap companies make them, but they seem to be pretty rare.
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The type of compressor is a bigger factor in efficiency. That, and is the system clean and properly charged.
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I have seen portable systems claiming an EER of 12. I think this is based on the cold air coming out and does NOT consider the thermal leakage. So just a rough guess, if the machine is radiating unwanted heat into your room at 100 W, and claims a cooling of 3 kW, then you should downgrade the EER by 3% ???
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