Cooking with tins?

^^^ "Then of course energy you use at home would depend how cooked. A pressure cooker is far quicker and cheaper than in an ordinary pan."

How does that compare to a slow cooker? So many variables!
Maybe we need to go back to Hayboxes?

Are slow cookers not a bit dangerous when cooking beans? Aren't they supposed to get up to a high temperature to kill off botulism? Just saying.