A jacket spud should never be microwaved.
We've got a clever microwave/oven/grill jobbie with a 'Jacket Tater' setting... Cooked and crispy in just a few mins...
We bought a stupidly expensive Miele bult in one. Here's a list of all the clever things it does
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I had a brilliant one in the UK (Panasonic?) that you just selected jacket tater and it did them perfectly... That was 20+ years ago...
When we came here we bought the Miele equivalent (micro/oven/grill) but being made in Greece it didn't have a jacket tater option but you could set it to full power
and oven to get the same effect...
In the apartment we have a clever 1,000W Panasonic again (bought from the UK) which has a jacket tater option but you have to weigh them and tell it what you are putting in... Seems somewhat of a backward step but it does cook them perfectly...