But if he is currently doing the porridge more expensively, he could well pay for the meter much more quickly once he realises that he should do it in the microwave instead of say on the stove hob.
More efficient than a nuke is to pass the power right through the porridge. Use an insulated pot & you don't need to reheat it. Note to anyone adventurous enough to try this: it can be done safely but a crude lashup can be deadly. Beware of toxic metal ions.
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