How long does it take to cook a jacket potato in the microwave?

In an 800 watt microwave, it takes 7-10 minutes (depending how big the potato is). A microwave with a lower wattage will take slightly longer. To stop the potato exploding during cooking, you should prick the skin of the potato with a fork/knife a few times on each side. Also, to ensure even cooking, turn the potato over halfway through the cooking time.