Devices using candle warmers such as fondue pots may be used if no other heat sources are available. Camp stoves and charcoal heaters. These may be used outside your home. Never use fuel-burning camp stoves or charcoal burners inside your home, even in a fireplace. Fumes from these stoves can be deadly.
Some frozen foods require considerably more cooking time and heat then canned goods.
Also, if power is off, it is best to leave the freezer door closed to keep food from thawing. Commercial canned foods can be eaten straight from the can. Do not use home canned vegetables unless you have the means to boil them for ten minutes before eating. Save liquids from canned vegetables. Substitute these for water in cooked dishes.