Rain and KWh per mile
- Thread starter hcdavis3
- Start date
Yep. But don’t know how much. On our commute guessing at 5 to 10 percent. Same as a gasser.
Derek Kessler
Active Member
Yes. Well, technically it's that the road is wet that hurts efficiency. A wet road is "stickier" when it comes to rolling resistance, which means the motor must use more power to turn the wheels.
Absolutely. It's a significant effect. On one long drive between Superchargers it started raining just as we left, with maybe a 25%-30% margin estimated by the nav using the previous dry conditions. We had to slow below the speed limit most of the time in order to arrive at our next stop with 10% remaining. Of course some of that slowing was required just due to the rain, but we had to slow more than that, and follow behind trucks to keep our 10% margin.
M3BlueGeorgia
Active Member
Light rain doesn't seem to have any measurable effect, but torrential rain can impact you, maybe by 20%.
We are talking about the rain that's so hard that you'll be slowing down for it, and also be watching out for water pooling on the road.
We are talking about the rain that's so hard that you'll be slowing down for it, and also be watching out for water pooling on the road.
Wooloomooloo
Member
Pretty much as others have said, along with inclines, wind and temperature, rain has one of the largest impacts on range. It's effectively because the tires/wheels have to push the denser water out of the way on the road before moving forward. As an aside, summer tires will suffer more than all-seasons because the tread is smaller. Also air with high humidity has greater density than dry air.
It's hard to quantify how much, it depends on other factors, but if you're typically getting 250Wh/mi, light rain alone might increase that to 260 - 270Wh/mi and heavy rain more so. If you combine that with cold, you could end up adding 50Wh/Mi quite easily.
It's hard to quantify how much, it depends on other factors, but if you're typically getting 250Wh/mi, light rain alone might increase that to 260 - 270Wh/mi and heavy rain more so. If you combine that with cold, you could end up adding 50Wh/Mi quite easily.
I average around 125Wh/km on my home-work trip in the 3 weeks that I have my car now. I drove 2 times in heavy rain, and the average of those drives came to 175Wh/km. I have to mention that the training days were also colder than the dry days, which would have lead to increased use of the heater since I just put that in auto on 20,5C.
Actually wet roads are less sticky (that's why tires have less traction when wet).
In case the link does not work, in a nut shell, the tire is constantly trying to climb up on top of the water (i.e. trying to hydroplane)
If you're not driving to fast, the tire fails to get on top of the water and has to push the water out of it's way to reach the pavement.
See the 2nd answer here.
Does a car consume more fuel when it's raining?
Enginerd
Member
Based on one trip where I encountered heavy rain and headwinds together, I measured about +35% Wh/mi. I now use this on top of my typical 15% battery comfort margin for road trips in adverse conditions.
It's a big impact. Even more so if the temperature delta outside is bigger. A cold temp will suck heat away from the car (water being a great thermal conductor), which will mean more heat is needed.
From my experience, I had almost a 50% increase in consumption when I had the following conditions:
~35-45F weather
Torrential downpour type rain
From my experience, I had almost a 50% increase in consumption when I had the following conditions:
~35-45F weather
Torrential downpour type rain
Wooloomooloo
Member
Well I never knew that. Additionally, rain is often associated with low pressure systems (which I did know) so even less density - I learned something new, thanks.
As that article says, it only makes about 1% difference typically, so far less than temperature or the additional tire resistance. Interesting nonetheless.
Any amount of water on the road increases rolling resistance. The tire must pump tread width times distance times water depth for each tire.
Example for Model S at 65 mph:
Equivalent mpg:
Smooth dry asphalt, no wind, no hills: 110.81
Light rain: 95.26
Medium rain: 88.83
Heavy rain: 83.90
At 35 mph:
Smooth dry asphalt, no wind: 166.37
Light rain: 133.81
Medium rain: 121.53
Heavy rain: 112.55
Numbers courtesy of Vehicle Energy Use Simulator Main
Example for Model S at 65 mph:
Equivalent mpg:
Smooth dry asphalt, no wind, no hills: 110.81
Light rain: 95.26
Medium rain: 88.83
Heavy rain: 83.90
At 35 mph:
Smooth dry asphalt, no wind: 166.37
Light rain: 133.81
Medium rain: 121.53
Heavy rain: 112.55
Numbers courtesy of Vehicle Energy Use Simulator Main
Yeah, it came up during a recent baseball game I was watching, and was a surprise to me, too.
Also note baseballs really carry at altitude (thin air) - anybody out there living at high altitude? You should be getting good KWh/m numbers at faster speeds, except of course you're probably dealing with big hills, which would be a negative!
