You don't try to heat an entire home, usually just a small room where you'll be spending a significant amount of time. I did something like this when I lost power for a few days in below freezing temps. A few candles going got the room to a comfortable temperature, it was I'd say a pretty average bedroom size, on the smaller side but not abnormally small.

If you completely insulate your home with a 1 inch layer of NASA’s aerogel, the heat output of a single tea light would eventually make it hotter than a kitchen oven. Just need to keep adding candle wax to that one tea light until the home is hot enough.