beatle
Well-known member
- Joined
- Jun 1, 2021
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- Location
- Springfield, VA
- Vehicles
- Model S, Ridgeline, Miata, motorcycle(s)
The drop in range is more from air density (cold air is denser) and rolling resistance than it is using the heat. I did some back-of-the-napkin calculations on air density and range on the TMC forum.
Similarly, people attribute poor gas mileage in the winter to the engine running richer at startup to bring the engine up to temperature - and this is true, but even on a long trip, mileage is worse. It's also true that an engine needs more fuel when getting cooler air to maintain the same air/fuel ratio, and that means more power (this is why cold air intakes are popular) but when cruising you only need as much power to overcome rolling and wind resistance to maintain your speed, so you'd just draw in less air to make the same power... unless you need more power to overcome more wind resistance in colder air (hint: you do).
Most are familiar with losing range in the winter, but it's often blamed on the fact that the cabin and battery heating elements consume power. This is true, but when I tested this last winter by driving 2 hours with a pre-warmed battery in cold temperatures and I only used the seat heater, I found my range didn't really improve much. In reality, air temperature makes a good dent on consumption for both ICE and electric vehicles. I used these two pages to calculate the wind load on a Model S at various speeds and temperatures. I set the drag are of the S to 0.575999 square meters and atmospheric pressure to 1 bar. Note: this is amateur hour since I am not an engineer, so maybe someone can check my math.
Wind Load vs. Wind SpeedWind load on surface - Wind load calculator.
Use the online air density calculator to find out the density of air at any given temperature and pressure.
Temperature | Air Density | Wind Speed (m/s) | Speed (mph) | Wind load (Newtons) |
32F (dry) | 1.27537 | 35 | ~78 | 450 |
80F 60%RH | 1.15273 | 35 | ~78 | 407 |
32F (dry) | 1.27537 | 27 | ~60 | 268 |
80F 60%RH | 1.15273 | 27 | ~60 | 242 |
The load is almost 11% higher in colder temperatures. Load is also a lot lower at lower speeds.
If you're just creeping through traffic or in complete standstill, your energy consumption will be very low. See videos from Bjorn Nyland on YT to see how much battery is consumed while maintaining cabin temperature. To the person who lost 20% in 30 minutes, you have other sources of battery loss, perhaps from the battery heater running if you started the car with a stone cold battery. I lose 20% battery in 30 minutes only when I'm driving at 70mph, and propelling the car down the highway uses way, way more energy than the cabin heater.Sponsored
