A hay box cooker (Google will find) is basically a well insulated box in which you place a bot of boiling food. The insulation keeps the pot hot for hours and keeps cooking. Think crockpot without a power cord!
This has many advantages:
* Only needs energy to bring the pot to the boil, not to keep it hot.
* Food cannot burn dry. Set it up in the mornign and come home to a hot meal in the evening.
* Fantastic slow slow cooker for rice, stews, legumes, cheaper meat cuts etc. and other budget/enviro friendly meals.
If you want, I can provide a simple diagram.