Like EVs, hybrids also lose fuel efficiency when it’s cold, AAA study finds
(From Automotive News)
Like
electric vehicles, hybrids also lose more fuel efficiency on a freezing day than a sweltering one.
But hybrids have an advantage over EVs when it’s cold — thanks, in part, to their internal combustion engines, according to new research this month from AAA. Still, their decline surprised the researchers.
Hybrids also trail EVs slightly in hot weather.
In 2019, AAA studied the effects of hot and cold weather only on EVs. This year, the group tested hybrids for the first time to see how temperature swings affect their efficiency.
Researchers gauged whether new EV technology, including heat pumps, has improved efficiency. While some systems might be more efficient, EVs on average performed much like they did in 2019, Greg Brannon, director of automotive engineering at AAA, told Automotive News.
AAA tested the electric
Chevrolet Equinox EV,
Ford Mustang Mach-E and
Tesla Model Y, along with the
Toyota Prius and hybrid variants of the
Honda CR-V and
Hyundai Tucson. The vehicles were run on a chassis dynamometer using temperature controls.
Researchers chose 75 degrees as the baseline temperature from which to measure hot and cold performance, and set the vehicles’ automatic climate control at 72 degrees for both heating and air conditioning. The goal was to mimic real-world scenarios, Brannon said.
Study clocks loss in miles
EVs lost about 10 percent of their miles per gallon equivalent, or MPGe, and 8.5 percent of their driving range when temperatures reached 95 degrees Fahrenheit, compared with a baseline of 75 degrees, according to AAA. Hybrids dropped 12 percent of their fuel efficiency in miles per gallon in the heat.
That energy loss was more significant when temperatures plunged to 20 degrees, according to AAA. EVs lost 36 percent of their MPGe and 39 percent of their range in the cold — a slight improvement from 39 percent of MPGe and 41 percent of range in 2019. Hybrids’ fuel economy fell 23 percent.
That cold weather sapped so much energy from hybrids was more than expected, Brannon said.
Both full EVs and hybrids use traction batteries, which are sensitive to temperature and are less efficient in cold weather. Hybrids use smaller batteries and can capture heat generated as engine waste.
“BEVs generally exhibit a larger cold-weather penalty because heating energy must be supplied electrically and because battery efficiency and power capability degrade at low temperature,” AAA wrote. “HEVs also lose efficiency, but waste heat from the engine provides cabin heat and reduces the need for high auxiliary electrical loads.”
Automakers often focus on heating or cooling the cabin as quickly as possible for occupants’ comfort, Brannon said, which is “a perfectly reasonable strategy” but trades off with efficiency.
“Most customers are probably not going to argue with that strategy,” he said. Drivers would “probably take a little hit in economy or range to get comfortable as quickly as possible.”
Finding a balance between comfort, efficiency
Hyundai engineers focus on that balance — a comfortable cabin, efficiency and range — when working on their hybrid systems, spokesperson Michele Tinson told Automotive News. It’s an ongoing process that aims to improve each vehicle in its lineup.
“As Hyundai continues to expand its electrified portfolio, we’re applying lessons learned across hybrids, plug‑in hybrids, and battery‑electric vehicles to further improve thermal efficiency, battery performance, and overall real‑world usability in all climates," Tinson said.
At Honda, fuel efficiency and comfort are configured “based on information from inside and outside the cabin, enabling effective use of the heat released from [the] engine,” a spokesperson for Honda R&D told Automotive News.
General Motors’ EVs use a thermal management system that incorporates thermal devices, two coolant loops and a refrigerant loop, Chevrolet spokesperson Chad Lyons said. The goal is to provide the occupants’ preferred cabin temperature without compromising range.
“Our system keeps the battery pack within a carefully defined temperature window so it can support optimal charge and discharge performance without using unnecessary energy,” Lyons said. “A key part of that strategy is reusing available heat — including waste heat from power electronics and other vehicle systems — instead of generating extra heat whenever possible."
Cold weather also takes a greater toll on drivers’ wallets, according to AAA. Hybrids required an extra $28 to fuel per 1,000 miles driven when it was 20 degrees than when it was 75 degrees, while EVs cost $32 more to charge at home and $77 more at a public charger.
At 95 degrees, EVs cost nearly $7 more to charge at home and $16 more at a public charger, compared with about $13 more for hybrids, AAA found.
Steps drivers can take to improve efficiency
Vehicle owners can take some steps to minimize energy loss. Drivers who can charge at home can precondition the battery and the cabin while the vehicle is still plugged in, Brannon said. That’s an important step in both hot and cold weather, but particularly in the cold, he said.
People also can use the heated seats and steering wheel, which target the driver more efficiently than warming the entire vehicle when the back seat is empty, Brannon said.
Automakers and regulators should consider giving consumers more information about cold-weather performance, and include city and highway driving on EVs’ window stickers, he said.
“We want to have people embrace these technologies in a way that builds them into their daily life and use case,” Brannon said. “The better information that people have heading into it, the better the experience will be.”
. And some road rage to make it angry
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