I don't see any way electricity could fall anywhere near that much in 20 years. For that to happen, we either need a revolutionary decrease in the price of nuclear power, a radical improvement in the price of dependable renewable energy (probably involving a lot of batteries) or some hard AI takeoff that makes EVERYTHING cheaper.
Keep in mind that most countries are trying to electrify most parts of the economy, so we not only need to decarbonize the current electrical supply, but possibly 2-3 times that, if we are to replace NG for heating, steel and chemical industries, fertilizers and so on.
Keep in mind that even if the technology for producing windmills and batteries go down a lot, we still need a lot of new mining capacity to even have enough raw materials to produce those items. That alone could take 10-15 years to build out.
