How do tailpipe emissions compare between PHEVs and gas-powered cars?

How do plug-in hybrids compare to battery-electric cars for greenhouse gas emissions? – Ivan, Calgary
For some Canadian drivers, plug-in hybrids might seem like the best of both worlds – but they might not be as good for the planet as advertised.
“They’re just not as impactful at cutting carbon pollution in our transportation sector as full battery-electric vehicles,” said Joanna Kyriazis, director of public affairs at Clean Energy Canada, an environmental non-profit based out of Simon Fraser University in Vancouver, B.C. “A lot of [emissions] estimates assume that drivers charge their cars way more and use their combustion engines way less than people actually do in reality.”
Plug-in hybrid electric vehicles (PHEVs) have bigger batteries than conventional hybrids, so you can drive them mostly on battery power until that runs out; then they switch to gas. Unlike with battery-electric vehicles (BEVs), there’s no range anxiety – as long as you can find a gas station. But while the battery in a conventional hybrid is charged by the car as you drive, a PHEV battery needs to be plugged into a charger to fully charge.
Of the 45 PHEV models for 2024 listed on Natural Resource Canada’s website, the Mercedes-Benz GLE 450e SUV has the greatest electric range, at 77 kilometres. The Lamborghini Revuelto, with up to eight kilometres of estimated range, has the least.
Even a limited electric range can appeal to drivers who find BEVs inconvenient or who worry about range and the availability of public chargers.
“You still have the gas engine under the hood for going to your aunt’s house in Sarnia or taking a road trip,” said Robert Karwel, a senior manager at J.D. Power’s Canadian office. “There’s no doubt about your ability to own this car and just drive it like a regular combustion-powered car … and they’re cheaper [to buy than a BEV].”
While BEVs have zero tailpipe emissions, PHEVs still emit CO2 – but, officially at least, considerably less than conventional hybrids or gas-powered vehicles.
For instance, according to Natural Resources Canada, the 2024 Toyota RAV4 Prime PHEV, which has a 68-kilometre electric range, emits 44 grams of CO2 per kilometre.
Compare that to 199 grams for the gas-powered RAV4 and 139 grams for the hybrid RAV4.
Or, compare the 2024 Mitsubishi Outlander PHEV’s 70 grams of CO2 per kilometre to the purely gas-powered Outlander’s 208 grams per kilometre.
The Revuelto comes last here again, with 472 grams of CO2 per kilometre.
Emissions omission?
Carmakers supply those numbers using testing standards from the U.S. Environmental Protection Agency (EPA) – Canada uses the same standards. For PHEVs, the standards assume that the drivers are charging their vehicles before driving them.
But a 2022 study by the International Council on Clean Transportation (ICCT), a U.S.-based watchdog, showed that drivers use up to 67 per cent more gasoline and up to 56 per cent less electricity than EPA fuel economy numbers assume.
Another ICCT study showed that PHEV CO2 emissions could triple, even if you’re plugging in daily to recharge, with the heater on during cold weather. If you haven’t charged the battery, emissions are even higher.
Over all, several studies show real-world PHEV emissions are higher than the official numbers, Kyriazis said.
While PHEVs emit CO2, they are still considered zero-emissions vehicles (ZEVs) by Ottawa, meaning they qualify for federal rebates of up to $5,000, depending on their electric range.
Over the next 11 years, Ottawa will require car companies to sell an increasing percentage of new ZEVs – starting at 20 per cent in 2026 and rising to 60 per cent in 2030 and 100 per cent in 2035.
That will include PHEVs but not conventional hybrids, which run on gas but capture energy from braking to power a small electric motor that extends fuel economy. By 2029, 20 per cent of sales can be PHEVs – but they will need to have an electric range of at least 100 kilometres.
“The government is trying to incentivize automakers,” Kyriazis said. “If they’re going to continue with this [PHEV technology, at least make sure that ranges are enough that Canadians’ daily driving needs could conceivably be achieved fully with the electric battery.”
BEV sales are still growing over all, but not as quickly as some carmakers had anticipated. That has pushed some companies, including General Motors and Volvo, to tap the brakes on plans to be all-electric by specific dates. Some, including GM and Volkswagen, are now planning more PHEVs in their lineups.
“There are not a lot out there yet … but PHEVs like the RAV4 sell very, very quickly,” Karwel said, adding that some current PHEVs have years-long waiting lists. “But this might potentially be a large growth frontier.”
In 2023, Canadian PHEV sales increased by 80.5 per cent – to 45,090 from 24,990 in 2022, according to Statistics Canada. BEV sales increased by 41.5 per cent – to 143,661 from 98,620.
But BEV sales still outpace PHEV sales over all, Kyriazis said. PHEV sales grew to 2.6 per cent of the market from 1.7 per cent in 2023, while BEV sales grew to 8.4 per cent from 6.5 per cent.
“If you think of technology adoption, it speeds up exponentially for a while, but eventually you get to the point where you’re still growing, but it’s not exponential,” Kyriazis said. “[Increasing sales] from 1 to 2 per cent in a year is 100 per cent growth. Once you get to 10 per cent, you’re not going to jump to 20 per cent in one year.”
So, if some drivers are still balking at BEVs, isn’t it better for the environment to get more people out of gas guzzlers and into PHEVs – as long as they plug them in?
“There is still an emissions benefit. It’s not nearly as much as [BEVs], but there is one,” Kyriazis said, adding that PHEVs may be a step to widespread BEV adoption. “PHEVs are getting Canadians more familiar with the benefits of electric powertrains.”
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