When will the use of fossil fuel decline by 50%. My guess is 2034. 20% of vehicles use 50% of the fossil fuel. In light vehicles the technology is ready today. What is missing are the vehicles types like large SUVs and trucks that cover all use cases. That likely will be covered within 5 years. The cost savings will drive the pace of replacement 5 X the typical consumer.
For heavy trucks battery technology needs to improve a bit. TBD. But the candidates are in lab, likely one or two will see production.
Once fossil fuel consumption deceases by 50% consumers will notice gas stations closing and refineries shifting from gas and diesel to other products.
Utility companies love investing in grid up grades knowing they win market share from bit oil.