The end could be coming soon for cars as we know them.

To limit global warming to 1.5 °C, the 2015 international Paris climate agreement set 2050 as a worldwide deadline to reach net-zero greenhouse-gas emissions. That means gas-powered vehicles will need to be largely off the road by then. And since cars typically have a lifetime of 15 to 20 years, reaching net zero in 2050 would likely mean no new production of gas-powered cars after about 2035.

Several major car companies, including GM and Volvo, have announced plans to produce only electric cars by or before 2035, in anticipation of the transition. But not all automakers are on the same page.

Notably, Toyota, the world’s largest automaker, has emphasized that it plans to offer a range of options, including hydrogen-fuel-cell vehicles, instead of focusing exclusively on electric vehicles. A Toyota spokesperson told MIT Technology Review that the company is focused on how to reduce carbon emissions most quickly, rather than how many vehicles of a certain type it can sell. 

The company has continued releasing new hybrid vehicles, including plug-in hybrids that can drive short distances on electricity using a small battery. In November, Toyota announced the 2023 edition of its Prius Prime, a plug-in hybrid. 

Some environmental groups have criticized the company’s slow approach to EVs. To get to zero emissions, they argue, we will need all-electric vehicles, and the sooner the better. 

But in recent interviews, Toyota CEO Akio Toyoda has raised doubts about just how fast the auto industry can pull a U-turn on fossil fuels, calling the US target of making EVs reach half of new car sales by 2030 a “tough ask.” While Toyota plans for EV sales to reach 3.5 million by 2030 (or 35% of its current annual sales), the company also sees hybrids as an affordable option customers will want, and one that can play a key role in cutting emissions. 

A tale of two hybrids

Two different categories of vehicles are referred to as hybrids. Conventional hybrid electric vehicles have a small battery that helps the gas-powered engine by recapturing energy during driving, like the energy that would otherwise be lost during braking. They cannot drive more than a couple of miles on battery power, and slowly at that. Rather, the battery helps boost gas mileage and can provide extra torque. The original Toyota Prius models are among the most familiar traditional hybrid vehicles.

Plug-in hybrid vehicles, on the other hand, have a battery about 10 times larger than the one in a traditional hybrid, and that battery can be plugged in and charged using electricity. Plug-in hybrids can typically run 25 to 50 miles on electricity, switching over to their gasoline engine for longer distances. The Prius Prime, introduced in 2012, is a plug-in hybrid.

Conventional hybrids are far more common in the US than either all-electric or plug-in hybrid vehicles, though sales of electric vehicles have grown quickly over the past several years. 

Hybrid vehicles are a straightforward story when it comes to climate effects: switching from a fully gas-powered vehicle to a hybrid version of the same model will mean reducing emissions about 20% while driving. 

Plug-in hybrids and EVs can be responsible for more significant emissions cuts, though figuring out exactly how much they’re helping the climate can be an involved exercise. The answer largely depends on driving and charging habits, says Georg Bieker, a researcher at the International Council on Clean Transportation (ICCT). 

Not surprisingly, electric vehicles produce less in lifetime carbon emissions than their gas-powered counterparts. A significant fraction of an EV’s emissions are attributable to manufacturing, especially the production of their batteries. Total emissions from EVs also depend on the sources of electricity used to charge their batteries.

EVs in the US correspond to between 60% and 68% lower lifetime emissions than gas-powered vehicles. In Europe, savings are higher, between 66% and 69%. In China, where the grid is powered by a higher fraction of highly polluting coal power, cuts are lower, between 37% and 45%. 

The gap between EVs and gas-powered vehicles is only expected to grow as the grid comes to be powered more by renewables and less by fossil fuels like coal. For example, EVs that hit the road in China in 2030 could produce 64% less in lifetime emissions than a gas car, compared with a maximum saving of 45% today.

Plug-in hybrid vehicles can offer significant emissions savings too: as much as 46% (compared with gas-powered vehicles) in the US. 

The difference between the US and other markets in the climate impact of plug-in hybrids, Bieker says, largely comes down to driving habits. Gas-powered vehicles in the US have higher fuel consumption, so there’s a bigger impact from switching to electricity. 

Driving and charging habits are at the heart of the debate over plug-in hybrids: the vehicles’ climate effects, depending on how they’re used. In ideal cases, the vehicles can use electricity for most of their mileage. Most new plug-in hybrids today have a range of between 30 and 50 miles on electricity, which is enough for many people’s daily commuting needs, says David Gohlke, an energy and environment analyst at Argonne National Laboratory. 

“I’m not necessarily a representative example of how someone uses the vehicle, but my plug-in hybrid is an electric vehicle for nine months of the year,” Gohlke says. He plugs in his vehicle every day when he gets home, which usually provides enough power to get him to and from work. Cold weather can limit the range, so he tends to use more gasoline in the winter, he adds. 

Drivers of plug-in hybrids can vary widely in their habits, however. “There’s a large gap between what is assumed in regulation and what the real performance looks like,” says Zifei Yang, head of light-duty vehicles at the ICCT. While some official EU estimates assume that drivers use electricity about 70 to 85% of the time, self-reported data show that the share for personal cars is closer to 45 to 50%. Drivers in the US have similar charging habits. 

The road forward

In the recently passed Inflation Reduction Act in the US, new tax credits apply to both plug-in hybrids and electric vehicles, provided they meet requirements on price and domestic manufacturing. 

But in other major markets, policy pushes are favoring electric vehicles over plug-ins. Some European nations, like Germany, are beginning to phase out subsidies for plug-in hybrids. In China, subsidies for plug-in vehicles are lower than those for electric vehicles, and they require a minimum electric range of around 50 miles, Yang says.

The various policies reflect differences in consumer attitudes: in particular, many Americans are still reluctant to buy EVs. 

Lack of access to charging, as well as concerns about range, are among the leading reasons US consumers say they wouldn’t consider an electric vehicle, says Mark Singer, a researcher at the National Renewable Energy Laboratory. Those concerns have made some consumers more receptive to plug-in hybrids than they are to electric vehicles, he adds.

In the US, there are just over 6,000 fast charging stations, and about 50,000 total locations that house EV chargers, as of the end of 2021. By comparison, there are about 150,000 fuel stations for gas-powered cars. Charging access is still a concern for many drivers, especially along interstate highways, where only 6% of EV charging stations are located. 

Today, a driver could easily go hundreds of miles between fast charging stations, especially in rural parts of the country. But the picture is changing quickly: the total number of charging stations has doubled in just the last few years in the US, and new federal funding will continue to support the network’s growth.

The transition from internal-combustion engines is well underway. EV sales continue to grow: they hit 10% of global sales in 2022. The picture isn’t the same everywhere, though: China saw nearly double the global average, at 19%, and the US lags behind at 5.5%. 

The EU recently banned new sales of gas-powered cars, including plug-in hybrids and anything else that can burn fossil fuels, starting in 2035. California and New York enacted similar bans that also take effect in 2035, though sales of some plug-in hybrids will still be allowed there. 

Transportation’s decarbonization won’t look the same everywhere. How plug-in hybrids fit in with this transition remains to be seen, especially in the near term, and especially in markets that haven’t yet passed strict regulations around future vehicle sales. 

Even if the relatively modest emissions cuts that hybrids contribute don’t align with aspirational climate goals, people may still turn to those cars, at least for the near future. Toyota, for one, is betting that plug-in hybrids, along with conventional hybrid models, will find acceptance among consumers. And it’s hard to argue that the world’s largest automaker doesn’t know how to sell cars.