Efficiency on mostly flat highways

[alozzy]

Air density is proportional to atmospheric pressure, but inversely to temperature and humidity.

So a hot humid day in New Orleans could have an air density like a cold, dry day in Denver.

Which is why I qualified my statement about air density with:

... assuming all other things are equal ...

Given similar atmospheric conditions (temperature, humidity, etc), air density at 5000' (Denver) is roughly 15% lower than at sea level. So, on average, an EV in Denver will go farther per kWh than an identical one at sea level, all other factors assumed equal.

 

[Marktm]

Data points in the South East Texas area:
- Mostly flat land
- Wind varies, but usually mainly a cross wind
- 63-65 mph on highway
- few small towns along the way
- 100 miles each way
- some gravel roads (3-4 miles)
- close to Sea level (~100 feet)
- ~40 psi tire pressure (stock)
Back calculated mi/kWh using LS's kWh data and miles (pay no attention to GOM - although much better correlations than in my 2012 leaf :mrgreen: )
Every "trip" has varied between 3.8 and 4.0 mi/kWh
All "suburban" estimates have been over 4.1 and up to 4.5 mi/kWh

 

[lorenfb]

Air density is proportional to atmospheric pressure, but inversely to temperature and humidity.

So a hot humid day in New Orleans could have an air density like a cold, dry day in Denver.

Which is why I qualified my statement about air density with:

... assuming all other things are equal ...

Given similar atmospheric conditions (temperature, humidity, etc), air density at 5000' (Denver) is roughly 15% lower than at sea level. So, on average, an EV in Denver will go farther per kWh than an identical one at sea level, all other factors assumed equal.

And that's the problem with these silly efficiency comparisons!

 

[alozzy]

Air density is proportional to atmospheric pressure, but inversely to temperature and humidity.

So a hot humid day in New Orleans could have an air density like a cold, dry day in Denver.

Which is why I qualified my statement about air density with:

... assuming all other things are equal ...

Given similar atmospheric conditions (temperature, humidity, etc), air density at 5000' (Denver) is roughly 15% lower than at sea level. So, on average, an EV in Denver will go farther per kWh than an identical one at sea level, all other factors assumed equal.

And that's the problem with these silly efficiency comparisons!

You should use more exclamation points when you post, it really helps to get your point across.

 

[lutefisk]

Living in Boulder it is assuredly *NOT* flat here, and I've averaged just under 4.5 mi/kWh for the 6+ years I've had the car.

Less dense air due to altitude definitely helps your car to achieve that level of efficiency. It's extremely difficult to achieve better than 4.2 miles/kWh at sea level when driving highway speeds.

Good point. I don't drive highway speeds much but the elevation changes kinda make up for that.