Several nations have enacted strict fuel economy standards but, for the most part, they have not required automakers to sell electric cars.
In the U.S., only the state of California has a zero-emission vehicle mandate that puts such a requirement on carmakers.
Yet even without mandates, automakers may soon be forced to sell large numbers of electric cars just to meet fuel-economy rules.
That's the conclusion of a study published in June by the World Energy Council (WEC), which argues that automakers will need quite a lot of electric cars indeed.
Among the major the points in the full study (pdf) is a prediction that 16 percent of cars sold in 2020 will have to be electric in order to meet emissions standards.
The study compares emissions-reductions targets for the U.S., China, and the Europe Union—the world's three largest car markets, with anticipated fuel-economy improvements that can be achieved with internal-combustion engines alone.
By the WEC's estimation, larger volumes of electric-car sales will be needed to plug an "EV Gap" between fuel-economy targets and the improvements that can be realistically expected from internal-combustion engines.
The size of that gap varies for each of the three markets studied.
In the U.S., it translates to 0.9 million cars, or 11 percent of estimated 2020 new-car sales.
For China, the gap is 5.3 million cars, (22 percent of estimated 2020 sales), while in the European Union it is pegged at 1.4 million (10 percent of sales).
However, significantly increasing electric-car sales will not be easy, as electric-car adoption is still hampered by consumer concern over cost and range anxiety, the study notes.
The WEC recommends increased incentive programs as a way to generate more electric-car sales.
The group's electric-car study also examines the potential effect of mass adoption on electric utilities and their grid infrastructure.
It predicts that annual increased electricity demand from new electric cars will be equivalent to less than 0.5 percent of total 2014 electricity demand in the three markets studied.
By 2020, all three markets will need to add some extra generating capacity to handle larger volumes of electric cars, according to the study.
It says electric cars will require an additional 4.5 terawatt hours in the U.S., 3.7 TWh in the EU, and 26.2 TWh in China.
This story originally appeared on GreenCarReports.