What's your average m per kWhr?

I've got about 4500 miles on my 2017 Rex and I'm running an average of 3.3 miles per kWh. I run almost exclusively in Ecopro.

As a North America driver in the North East, until recently most of my driving was in the winter since I picked up the car just before the end of the year.

What are you all seeing? Is this reasonable?

Driving efficiency comparisons are valid only under similar driving conditions. The lifetime average for our 2014 BEV is ~5.5 mi/kWh, but that's in a nearly perfect EV driving environment where temperatures rarely drop below 60º F and rarely rise above 90º F, driving speeds are typically 40 mph and never exceed 65 mph, few miles have been driven on hilly terrain, and driving is always in EcoPro with AAC on.

How do you see lifetime consumption?

I am assuming you are quoting from the battery, what car shows under "consumption"? Not from the wall?

The i3 is very efficient, surprised I am consistently getting about 30% better than my Volt.

viking79 said:

How do you see lifetime consumption?

Click to expand...

BMW's deprecated iRemote app reports lifetime efficiency. The latest version of the BMW Connected app tries to do so also but a bug results in the nonsensical lifetime efficiency value of 19.3 mi/kWh with a community average of 15.3 mi/kWh.

When I last used iRemote a couple of years ago, the lifetime efficiency of our i3 was 5.5 mi/kWh. I just reinstalled iRemote. It now reports a lifetime efficiency of 5.1 mi/kWh, but it also reports that our i3 has been driven only 2,074 miles instead of the actual 6,484 miles. So I'm skeptical of iRemote's data now although we have been using climate control more in recent years which probably means that our lifetime efficiency value is less than 5.5 mi/kWh.

viking79 said:

I am assuming you are quoting from the battery, what car shows under "consumption"? Not from the wall?

Click to expand...

Correct. The Idaho National Laboratory measured an i3's charging efficiency ranging from a low of 84.1% for 120 V 5.6 A charging to a maximum of 93.4% for 240 V 30.1 A charging. Our EVSE charges at 208 V 16 A which should be ~92% efficient based on the 208 V efficiency measurements made by the Idaho National Laboratory.

viking79 said:

The i3 is very efficient, surprised I am consistently getting about 30% better than my Volt.

Click to expand...

The Volt is considerably heavier but might have lower aerodynamic drag. I would expect an i3 to be more efficient than a Volt in low-speed stop-and-go driving but maybe less efficient at highway speeds on relatively flat roads.

My personal average is 4.0. I can see over 6 on a mild summer day at lower speeds, and I"ve seen as low as 2.9 on a really cold day, high speeds, and no preconditioning. It really can vary radically depending on the conditions and your use patter, similar to an ICE.

Regarding the miles to empty...I had occasion to drive my ICE yesterday...started out showing 375 miles to empty. I drove 30-miles, and it said 380 miles to empty...different driving conditions, different results based on previous uses. The i3 will give you similar percentage changes, depending on conditions and driving modes.

My mi / kWhr reading is coming from the i3 display.

When I picked up the car in December, the display showed 2.9 m/kWhr.

I just finished a longer trip where I spent maybe 50% of the trip on highways traveling at 75 mph. The average as shown on the i3 display is now 3.4 m/kWhr. So I guess this average reading will slowly creep up.

BTW I travelled 118 miles on a charge on this last trip and didn't have the Rex turn on. Which I'm pretty happy with.

If I remember, you can show average and instantaneous values which you can reset...press in the end of the stalk when the value you are interested in is being displayed and it will start from then. If you have the app, you can see your last trip's values and your overall average since the car came into service.

Low speed in moderate temps should see much higher than what you saw unless you're always using max acceleration and using the brakes rather than regen, or live in really hilly country.

I'm using a Juicebox pro for the EVSE. Has anyone found a device like the Killa-watt that can be used in a 14-50 plug to measure actual power usage? I have a standard 110v Killa-watt I use around my home, but to measure power consumption on the Juicebox, it'd need to be rated at 220v at 50 amps.

jadnashuanh said:

My personal average is 4.0. I can see over 6 on a mild summer day at lower speeds, and I"ve seen as low as 2.9 on a really cold day, high speeds, and no preconditioning. It really can vary radically depending on the conditions and your use patter, similar to an ICE.

Regarding the miles to empty...I had occasion to drive my ICE yesterday...started out showing 375 miles to empty. I drove 30-miles, and it said 380 miles to empty...different driving conditions, different results based on previous uses. The i3 will give you similar percentage changes, depending on conditions and driving modes.

Click to expand...

Yes, I have been watching the average and instantaneous readings by pushing the left stalk button. I find the instantaneous reading to be super sensitive so I normally leave it on average.

I try to use regen braking as much as possible. This is an incredible feature of the i3 (except when it shuts off around a curve).

As for the 'miles to empty', I seem to remember after charging overnight, the i3 display estimated 108 miles. But I did 118. I find 'miles to empty' to be not very accurate and instead I use 'percentage' charge and do a mental calculation on miles available (example: 60% of 110 miles is 66 miles available).

Nyken said:

I try to use regen braking as much as possible. This is an incredible feature of the i3 (except when it shuts off around a curve).

Click to expand...

Actually, coasting (power gauge centered with no regen or power) is the most efficient way to decelerate followed by using regen which is considerably less than 100% efficient at recovering energy. Of course, the least efficient is to use friction brakes.

I test drove one i3 with 23k miles that showed an average of 2.8!
When I bought my '15 it showed 3.6. I reset the statistics using the BMW connected app and now I'm at 4.3. I use Eco Pro mode mostly with Eco Pro+ when the traffic and weather conditions allow and only a very occasional use of Comfort.

Today I tried Alohart's suggestion about monitoring the instantaneous mi/kWhr, and was surprised to see that regeneration of power is strongest when you decelerate the least!

This is counter intuitive, since I would expect faster deceleration when regenerative braking would charge the battery faster.

In fact what I saw was that rapid deceleration, by completely removing my foot from the accelerator, regenerated power at a rate of 1.9 mi /kWhr. While a slow, easy deceleration, where my foot stayed partially on the pedal, regenerated at a rate of between 4 and 99 mi/kWh.

I believe the i3's power indication of mi / kWhr is pretty accurate since measuring electrical power of D.C. Voltage is easy to do.

What the heck does mi/kWh mean for regeneration anyway? Their recuperation figure confuses me. Why don't they use kW like normal people?

Nyken said:

In fact what I saw was that rapid deceleration, by completely removing my foot from the accelerator, regenerated power at a rate of 1.9 mi /kWhr. While a slow, easy deceleration, where my foot stayed partially on the pedal, regenerated at a rate of between 4 and 99 mi/kWh.

Click to expand...

I had to go figure out what that ridiculous number meant, lower number is higher regeneration. See this:
http://www.mybmwi3.com/forum/viewtopic.php?t=1502

So 20 mi/kWh means you are recuperating battery energy at a rate of 1 kWh per 20 miles driven. A low number, like 5, means you are recuperating 1 kWh every 5 miles driven (4 times as fast).

Eric

Does it really mean this? I thought it would be 20 miles driven in recuperation mode, not just driven.

viking79 said:

Why don't they use kW like normal people?

Click to expand...

kW is a power unit which is an instantaneous measurement. mi/kWh or kWh/100 km is averaged over a time period which gives one a better indication of how one is driving over time.

Nyken said:

Today I tried Alohart's suggestion about monitoring the instantaneous mi/kWhr, and was surprised to see that regeneration of power is strongest when you decelerate the least!

Click to expand...

You're interpreting recuperation incorrectly. Smaller mi/kWh values indicate higher regeneration rates which would be less efficient than deceleration via coasting (i.e, no regeneration, so the kWh denominator is 0 making mi/kWh very large).

"Lower number means higher regeneration"

Ah, my faith in the universe is restored. Thanks for pointing this out, Eric.

I'm perfectly happy monitoring mi/kWhr on the i3 since kWh is what I see every month on my electric bill. So I can relate.

But people who have a Tesla monitor the inverse: watts consumed per mile. For them, a lower number means better efficiency (300 watts per mile is more efficient than 400 watts per mile).

The efficiency value probably should have changeable units, like the display of miles and kilometers, since its simply a calculated number.

alohart said:

viking79 said:

Why don't they use kW like normal people?

Click to expand...

kW is a power unit which is an instantaneous measurement. mi/kWh or kWh/100 km is averaged over a time period which gives one a better indication of how one is driving over time.

Click to expand...

That is what, instantaneous regen value. Maybe a total kWh regenerated. Would be more useful to me.

You need to look at your use and regen as a package. Ideally, you'd have both high miles/KwHr AND miles/KwHr...this means you're not wasting energy by slowing down, but anticipating your required stops and coasting while getting long distances on each KwHr used. It takes a fair amount of energy to accelerate to speed and regen is never as efficient, so there's always a loss involved. Your best, most economical driving would be to get up to speed and hold, and, if you do need to stop, coast as much as possible.

Another way to look at the miles/kw regen is that if you were driving at a perfectly steady speed on a perfectly level road, you could go until you ran out of battery charge, and maybe get 100+ miles and only regen once when you essentially coasted to a stop at the end. A high miles/kw regen associated with a high miles/Kwhr used implies greater efficiency. In stop and go, if you never used your brakes, your miles/kw regen would be a much shorter distance. That same driving if you used your brakes rather than regen, that number of miles would grow.

The worst combination is lots of stop and go at high acceleration rates and the use of brakes heavily at the last moment, then the miles/kwhr would be small, and the miles regen would be high.