There's a funny comment downthread that says "It's like the backyard furnaces during the Great Leap Forward."
Everyone replying disagrees, but I think it's a perfect analogy: just like the backyard furnaces, these small-scale installations are inefficient, provide a negligible portion of total energy needs (<1% of total energy needs if everyone in Germany did it, from TFA), look ugly and - this is the most important - provide the feeling of doing something about a serious problem without actually doing anything substantial.
Everyone replying disagrees, but I think it's a perfect analogy: just like the backyard furnaces, these small-scale installations are inefficient, provide a negligible portion of total energy needs (<1% of total energy needs if everyone in Germany did it, from TFA), look ugly and - this is the most important - provide the feeling of doing something about a serious problem without actually doing anything substantial.