Solar panels and wind turbines generate around 5W/m2. So some way to go but this is a brand new technology.
A happy is effect is sucking out electrons reduces te production of methane from plants so it’s combined electricity production and methane reduction is a double positive whammy to help the planet avoid global warming.
Amazing stuff because green electricity producing roofs also provide great insulation, rainwater storage, help urban sustainable drainage, and are useful animal habitats.
Hopefully this technology will take a lot less than the usual 50 years to become ubiquitous.