E solo un tentativo. Senza il contesto non si sa come rendere l'espressione.

se è un modo di dire e non lo vuoi tradurre con un proverbio corrispondente (ma che magari usa parole diverse per costruire la metafora), che ne dici di 'stufa senza fiamma'?

se l'argomento tratta di cucine allora il termine tecnico é proprio "piano cottura"

un contenitore per mantenere i cibi caldi, come un "thermos"

• Utilizing fireless cookers: a cooker that requires no energy source but the heat in the food itself! (If there are a couple really eager students they could manufacture one.)


http://www.florilegium.org/files/FEASTS/fd-transport-msg.htm...
Fireless cookers
The simple haybox and the more elaborate hotbox are fireless cookers. They work in the same way as a vaccuum flask, retaining heat by insulation.
Once a pot of soup or stew has been brought to the boil, it is placed inside the insulated box, where it continues cooking for several hours without using any further energy. This slow cooking method is ideal for dishes like soups, stews, porridge, rice, grains and casseroles. You can use it to keep water or cooked food warm and to make yoghurt.