The problem, of course, is intermittency. The sun shines brightly enough to produce feed-in energy for utilitites for an average of three hours a day in most climate zones. The wind blows and then it doesn't. While these weather effects are occurring, renewable electricity is generated and can be used. This intermittent availability is beneficial when, for instance, energy from the hot summer sun can be used to alleviate electrical demand from air conditioners.
But what about the rest of the time? Can't solar and wind energy from peak production times be stored in batteries to power our communities for the rest of the day and night? Not even close. The best battery in existence stores 36 MW of power for 15 minutes--enough to run 35,000 homes for that interval--and costs $44 million. More efficient energy storage systems and smart-grids that connect renewable sources in farflung places are being designed and might eventually be operable, but that is a resource that largely belongs to the future, not the present.*
As every energy analyst knows, therefore, it's currently the case that solar and wind are only ever supplementary electricity sources alongside baseload power sources that fire all the time. Baseloads can be clean hydro-electric power or geo-thermal power. But in most circumstances the baseload is a fossil fuel energy source: either coal or natural gas. The truth is therefore that--at present and in the immediate future--expensive renewable energy investments will be able to reduce fossil fuel use but not replace it.
In contrast, there is one major atmospherically-green form of energy apart from hydro-electric power that completely replaces fossil fuel, and that is nuclear energy. I have written before on why we fear nuclear energy, probably irrationally. Though our fear of nuclear is understandable, it seems this fear is being leveraged as political currency in places like Germany, where leaders are ramping up popular support by shutting down nuclear power plants.
Another factor as well ought to be considered in the political equation, which is that in the current reality, transitioning from nuclear energy to renewable energy tends to intensify our dependence on fossil fuel energy as a baseload. As RFK Jr oddly put it, "Solar and wind plants are gas plants."
*Amendment: I have received a great deal of commentary on this point from supporters of 100% renewables who point out that there are scenarios for getting to a 100% renewables electricity grid without fossil fuels or nuclear. It does seem that in some places like Denmark and Iceland this might be possible as there is access to other operating forms of baseload energy, in particular hydro-electric and geothermal power. Achieving 100% renewables without baseload energy, through a combination of grid redesign, storage, novel energy forms, *and* demand reduction remains, however, a distant and difficult prospect. Take a look at the propositions here, for example, for a sense of their scale and complexity (e.g. a pan-European grid connected to North Africa!). Now think of the carbon building in the atmosphere each year, and consider whether it would not be more timely and practical to emulate France, which right now obtains 75% of its electricity from nuclear.**
**For what it's worth, I am a student in a public administration faculty and not affiliated with any energy entity.