The simplest thing would be to change how the driver app assigns jobs. Under certain conditions, when they look at the Uber driver app, drivers of gasoline cars

The simplest thing would be to change how the driver app assigns jobs. Under certain conditions, when they look at the Uber driver app, drivers of gasoline cars would just not see jobs available where drivers of electric cars (in the same location at the same time) would. Adjust conditions as necessary so that you hit your target (while also trying to minimize service disruption). Because Uber drivers can't make money if they can't accept jobs, this creates an incentive for drivers to have an electric vehicle. They can get jobs others can't. Eventually, the market should even work out the correct pricing. There's already a mechanism to pay more when drivers are in short supply. If the supply gets restricted because gasoline cars are sometimes ineligible, compensation has to go up (assuming Uber doesn't want to make customers wait forever for a ride).