Those who intend on taking a road trip this summer in a full-electric vehicle should take note: While it’s been widely circulated that driving in extreme temperatures – including the sweltering summer heat much of the nation is suffering – can take a heavy toll on an electric vehicle’s range on a charge, it’s not the worst kilowatt killer in this regard.
A recent study conducted by the automotive analytics company Geotab found that while running an EV’s air conditioning on a hot day can accelerate its energy consumption, driving at higher speeds can actually prove to be a more significant detrimental effect on its operating range.
Geotab’s experts mined telematics data from 350,000 trips in 500 battery-powered sedans, totaling over 180,000 hours of driving. It shows that even modest increases in an EV’s speed can result in a pronounced loss of battery capacity.
When last we checked, testing conducted by the Society of Automotive Engineers (SAE), determined that an EV can be expected to lose an average 17% of its effective range when the temperature reaches 95 degrees. Like an internal combustion vehicle, it takes additional energy to operate a car on a hot day with the air conditioning running, though the penalty tends to be more pronounced with an EV.
However, Geotab’s findings take a different tack by comparing vehicle speeds at higher temperatures. The researchers found that a full-electric sedan can expect a 28% drop in operating range at 86 °F when cruising at 80 mph versus 50 mph. At 50 mph an EV that has 277 miles of driving range, will drop to an average 251 miles at 60 mph, 226 miles at 70 mph and just 200 miles at 80 mph.
It may take an EV owner a bit longer to get to a far-flung destination driving at a slower speed, but doing so can ensure he or she will have that extra 77 miles of battery power to get there and perhaps avoid having to frantically find a working public charging station along the way when the state of charge runs low.
The laws of physics are working overtime here, with an EV’s aerodynamics largely coming into play. Just as it is in a conventionally powered ride, the faster a vehicle travels, the harder it has to work to combat an increasing amount of wind resistance.
Sleeker is better in this regard, with the Lucid Air EV’s svelte silhouette at around a 0.21 coefficient of drag, which makes it one of the slipperiest cars on the planet. Combined with an active rear spoiler that engages at higher speeds and other advanced technology. It’s EPA-rated as high as the electric equivalent of 142 mpg in highway driving.
According to Geotab’s analysis, doubling an EV’s speed requires four times the energy just to overcome the added wind resistance, which is more than its cabin air conditioning system will ever use.
Of course, vehicle speed is not the only factor in play at robbing an EV of range in hot weather. At lower speeds – especially in stop-and-go city traffic – where wind resistance is negligible, running the air conditioning becomes a more prevalent penalty. Ambient temperatures become an even more significant factor in winter, where tests have shown that EVs can lose as much as around 41% of their battery capacity at 20 degrees Fahrenheit and an even greater percentage at chillier ambient temperatures while running the cabin heater.
As with most of us, EVs prefer more temperate conditions, with the SAE’s data showing a zero loss of range while driving at 75 degrees.
“Modern EVs have increasingly large batteries, and many can comfortably handle most daily driving – including fleet routes – on a single charge,” explains Charlotte Argue, Geotab’s Senior Manager for Sustainability. “But range, on EVs or internal combustion vehicles, will always vary with real-world conditions: temperature, topography, traffic, and yes, speed.”
Whether taking an extended highway road trip or running errands around town, there are a number of ways prudent EV owners can help maximize their vehicles’ range on a charge, no matter what the thermometer reads:
- Slow down: Driving at 50 mph rather than 70 mph can boost battery range by 10-20%.
- Precondition: Cool or warm the vehicle while it’s still tethered to the grid to avoid taxing the battery after hitting the road.
- Avoid jackrabbit starts and sudden braking: The former uses more juice, while the latter misses the full effect of regenerative braking, which recovers energy that would otherwise be lost while decelerating and braking.
- Use the A/C and heater sparingly: Use the climate control system’s recirculating feature, set the temperature higher in summer and lower in winter, and switch on ventilated/heated seats to consume fewer kilowatts.
- Park in the shade: This helps keep the cabin cooler in the summer, which in terms means using less energy than to force the AC do all the heavy work to make sitting in it tolerable. Even better would be to park in an enclosed garage.
- Minimize junk in the trunk: Reducing any vehicle’s weight is the easiest way to boost its efficiency. Carrying an additional 100 pounds of cargo can increase a vehicle’s energy consumption by 1-2% percent.
- Charge at home: Use public charging only as needed. Not only are DC fast charging stations a costlier alternative to home charging, they tend to put a strain on an EV’s battery and frequent use can shorten its eventual life. Not only is home charging more convenient, some utility companies will charge customers a lower rate in non-peak hours, which can help reduce the cost of kilowatts.
- Tend to tires: As with a conventional auto, driving an EV with under-inflated tires will not only increase its energy consumption, but will lead to uneven and/or premature tread wear. Check the air pressure frequently using a simple tire gauge, as it can vary by an average of one PSI (pound per square inch) with every 10-degree (Fahrenheit) change in air temperature. Have them properly inflated according to the PSI recommended by the automaker. This information is usually noted on a sticker that’s affixed to the driver’s-side door frame.
