I’ve used a thermal imaging camera on a candle before to test this. A typical candle is producing heat but it usually outputs that heat straight up above the flame and hot wax, usually going right into your ceiling and getting pulled by the draft. If you want to actually get a useable amount of heat, add something to catch the heat. Clay pots work nicely, they catch the heat and have enough thermal mass to then slowly output it to the environment in a way you can really feel.

I’m currently living in a 1 room cottage down in Gansett, and a cheap candle with a clay pot above it and placed in the center of the room is enough to keep the heat off, down to about 45F outside temp. Now I’m starting to worry about my pipes freezing so the heats going on, but it worked in the fall!