Are wind turbines supposed to generate 840 kw? If so, that seems a bit high. They only take up a 2x2 space and are quite inexpensive, outputting almost the same energy as an entire steam engine. Would a configuration option for energy output be possible? I am personally using the 0.17 version, but I don't know if that would have anything to do with it.

change the prototypes\WindTurbine\entities.lua on line 11 from "35" to "1.35", this will make it seem like an upgrade after you unlock the tech.

If it doesn't get resolved in the mod itself, I've been thinking about making a small addon to reduce it so I can use the mod in multiplayer too. First though, got to work out the kinks in my existing mods. Still very much a beginner in modding.

For anyone else having issues with this until/unless the mod author fixes it, I have created a configuration mod for BioTech, which among other settings includes a setting to change the effectivity of the wind turbine.
https://mods.factorio.com/mod/PhotosynthesisAbsorbsCarbon