Not off grid, but can still function if the grid goes down. Kelly Kettles work really well if you need hot water out in the field. You generally need something to get them lit, paper, bit of oily rag unless your tinder is dry. Once going they do roaring flame out the top and can be kept going with twigs, whatever you can lay your hands on. Add a cross support on top and you can double duty cooking on it too.
I have couple here, the stainless one above and an older aluminium one. They must be 10yrs old or more. Always carry one in the car if we travel.
They are a bit like owning an old Tilley lamp, a must have if you enjoy the outdoors life. Just watch where you use a Kelly Kettle, they will leave a scortched circle if used on grass. Won't make you popular at a campsite.