Many people’s first choice for long-term storage of food is their freezer. However, in situations where it’s possible that the power supply may be interrupted, freezing food may not be such a good idea. For short periods of power loss, up to a few hours, it isn’t likely to be a big problem if you can keep the freezer door closed (i.e. if you don’t open it to take food out!). If the power is off for longer, though, you may have to discard much of your stored food.
The US FDA have a useful chart showing which food can be refrozen if it has thawed, and which cannot. If you don’t have a thermometer in your freezer, one handy tip is to fill a small container half-full of water, freeze it, put a coin onto the ice, fill the rest of the container with water and freeze it again, so that you have a coin frozen in the middle of a block of ice. If you open the freezer and find that the coin has sunk to the bottom of the container, the ice has evidently melted at some stage (even if it’s refrozen since) and you should suspect the food within.