Most people buy electric cars to reduce oil consumption, but oil companies keep selling more oil every year.

Now, a new study by oil industry consultancy Wood Mackenzie predicts that the demand for oil will start to decline as early as 2036, when autonomous cars become more popular. That forecast comes much earlier than many big oil companies predicted.

The report was initially covered by the Financial Times (subscription required).

READ THIS: Decline of oil: Bloomberg suggests what it could look like

Autonomous cars, which are widely expected to be mainly electric, will dramatically increase the number of miles driven on electricity and supplant miles driven on gasoline, the report suggests.

“Autonomous electric vehicles or robo-taxis will really change the face of transport in the coming decades,” Ed Rawle, chief economist at Wood Mackenzie told the FT.

Waymo Jaguar I-Pace

Waymo Jaguar I-Pace

“Each autonomous electric vehicle (is) expected to have a larger impact on curbing oil demand than a conventional electric car. They will be on the road far more as they are autonomous, displacing a disproportionate amount of oil-based transport,” he says.

Wood Mackenzie expects autonomous cars to be commercialized in 2030, but to take another few years before their use becomes widespread.

DON'T MISS: Even oil companies now acknowledge electric cars are coming

Rising fuel-economy standards around the world are expected to take a bite out of gasoline demand before overall oil demand peaks, the report notes.

New cars with better fuel economy have been rolling into the market since 2008, but it will take the retirement of many older cars from the overall vehicle fleet to begin reducing gasoline demand, the report says.

Rawle says many of Wood Mackenzie's oil-industry clients are expressing concern about peak demand for fossil fuels, and looking to bolster other lines of business, such as petrochemical manufacturing, to fill the gap.