At a burning rate of 2.5 kg soft pine wood per hour, their experiments showed an average power output of 4.2 watts

While they have more complex/expensive designs that produce 13 watts with cold water heatsink start, these devices are much more expensive than a 100w solar panel which would produce the same amount of energy on a bad winter day (1 hour total sun), even when the solar is professionally installed.

The amount of wood to burn is about 1 year of growth per day of heat + minimal electricity, and air quality in homw would be worse than North east cities during recent wildfires.