If you type in "testing candle heater" into jewtube, there are tons of videos proving that this works. It does take a while to heat up larger rooms and the general consensus is that you would need a setup in each room with the doors closed to be most effective. If you have a large open concept home, you're either SOL or will need a whole bunch of these set up in order to heat a large space, being prepared to replace the candles as soon as they go out.