There are different types of candles suitable for survival purposes.
Small tea light candles are great for small to medium size kits and you can pack several into a small plastic bag. They weigh almost nothing so you won’t notice them in your kit. They don’t last a long time once lit but they work great with helping to get a fire going.
Light the candle, then build your tinder and kindling around it. Or, construct your fire lay in such a way that you can push the tea light out once the fire is going. That way, you can blow out the candle and save it for use again later.
The gimmick birthday candles, the ones that relight themselves after you blow them out, also work well for fire making. They are pretty much single use, though, and don’t burn a long time. The advantage is they are small and you can pack a whole bunch into a small pouch.
There are, of course, candles that are specially designed for emergencies. Generally speaking, they are somewhat thicker than the ones you’d buy for a romantic dinner and thus they burn longer. However, due to their size, they aren’t suited for use in small kits.
You could also consider making your own emergency candle for a survival kit. Use an Altoids tin or another similar size metal container. Use broken candles or old crayons for the wax. Wicks can be purchased at any craft store.
Melt the wax in a clean soup can placed into a few inches of boiling water. Once melted, carefully pour the wax into the Altoids tin and as the wax begins to set, insert the wick. I usually do two or three wicks, placed evenly apart. This gives me the option of more or less light based on how many wicks I have burning.
A great time to go candle shopping is right after Christmas, when all sorts of holiday decorations are on clearance. You can pick up a bunch of candles for pennies on the dollar. In a survival situation, it really doesn’t matter if it is the middle of July and you’re breaking out the Santa candles, or April and enjoying Halloween colored ones.
Obviously, once lit, candles are an open flame and need to be treated with caution. Always be aware of what is near the candle and where it is positioned, lest you accidentally bump into it.
Personally, I like to use oil lamps and candle lanterns for emergency light in the home during a power outage, as they tend to be a bit safer. But, there’s no arguing that candles can be a very cheap and reliable source of emergency light, as well as a great way to help get a fire going.