0°F Commute Efficiency

[bdavis171]

Cold commute home this evening. 20" Blizzaks, All Purpose mode. Most of the driving was done between 30-40 mph on highway traffic. Efficiency taking quite a hit in these temps!

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[Jabbahop]

ouch. I found this blog post interesting about the multiple ways that cold temperatures impact car efficiency including non EVs.

http://alohonyai.blogspot.com/2014/11/effects-of-winter-on-fuel-economy.html

 

[Redmond Chad]

How long was the commute? Startup costs (warming up the cabin and battery, for example) can do terrible things to efficiency numbers for short trips. The longer you drive, the less it matters.

Many years ago I had a Honda Insight. I got anywhere from 46mpg to 82mpg on various round trips while I owned it; overall average was 62mpg. The worst-case 46mpg number was from 8-mile round-trip commutes with a very long break in the middle, so the car had to be heated twice. After adding a block-heater at home so it started warm on the first leg, the number went up to 55mpg.

 

[popoga]

I get that trash level of efficiency in 40F+ weather, those are rookie numbers.

 

[kizamybute']

Cold commute home this evening. 20" Blizzaks, All Purpose mode. Most of the driving was done between 30-40 mph on highway traffic. Efficiency taking quite a hit in these temps!

Using the heater in an EV is a range killer. Worse than AC. Add that to the fact that batteries don't like to be cold and while your photo did make me say "wow" when I saw the 0.87 miles per kw figure, I guess it's not that out of the ordinary for that cold of temperature where you certainly have the heat running. You're not only keeping yourself warm, but the truck is expending extra energy to keep the batteries warm too.

My rule of thumb for EV's has always been to ensure that 50% of the rated range will satisfy most of my daily needs. Assuming that to be the case, which it easily is for a large majority of people who will never travel more than 150 miles on their regular daily use.

If you're still satisfied with the truck, then you're in good shape as, aside from towing, you're experience about the worst part of EV ownership.

 

[Kuro-Rivian]

Hah, just wait until tomorrow! I got about just a smidgen over 1 mi/kwh this morning at -4. You can inflate up LT blizzaks. Up to 80s psi. They may ride like crap and not handle great....im saying you should but but it can be done. The tires can handle it. The LT tire equivalent psi to handle the max load of our truck and the AT tires is 46 psi. So the door placard recommendation works...just a tad high. Seems like my toyo winters like low 40s for max grip. I did run around with them at 65. While it got great range, it was a hard ride and grip wasn't so great!

 

[bdavis171]

Using the heater in an EV is a range killer. Worse than AC. Add that to the fact that batteries don't like to be cold and while your photo did make me say "wow" when I saw the 0.87 miles per kw figure, I guess it's not that out of the ordinary for that cold of temperature where you certainly have the heat running. You're not only keeping yourself warm, but the truck is expending extra energy to keep the batteries warm too.

My rule of thumb for EV's has always been to ensure that 50% of the rated range will satisfy most of my daily needs. Assuming that to be the case, which it easily is for a large majority of people who will never travel more than 150 miles on their regular daily use.

If you're still satisfied with the truck, then you're in good shape as, aside from towing, you're experience about the worst part of EV ownership.

I'm definitely happy with it, but I feel as though it's useful for others to understand how the Rivian performs in various conditions. If you are planning a road trip in the winter, these numbers can be quite helpful as a worse case scenario.

How long was the commute? Startup costs (warming up the cabin and battery, for example) can do terrible things to efficiency numbers for short trips. The longer you drive, the less it matters.

Many years ago I had a Honda Insight. I got anywhere from 46mpg to 82mpg on various round trips while I owned it; overall average was 62mpg. The worst-case 46mpg number was from 8-mile round-trip commutes with a very long break in the middle, so the car had to be heated twice. After adding a block-heater at home so it started warm on the first leg, the number went up to 55mpg.

It was about 20 minutes and yes, I'm sure the startup from preheating the truck contributed.

 

[Yellow Buddy]

Cold commute home this evening. 20" Blizzaks, All Purpose mode. Most of the driving was done between 30-40 mph on highway traffic. Efficiency taking quite a hit in these temps!

What was HVAC set at?

I've been playing around with different settings to try to figure out how much of the impact is due to heating the cabin vs heating the battery.

I haven't been down to 0F but just as an example - using heated seats for all 4 passengers vs HVAC at 70F (outside temp ~35F) resulted in 2.2mi/Wh vs 1.7mi/Whi at 70mph. With 4 we were all pretty comfortable still with body heat filling the cabin but I'm not sure that's feasible at 0F. Curious nonetheless.

 

[itselectric]

Dang. Just over 100 miles on a full charge. We really need a breakthrough in battery tech to handle this.

 

[bdavis171]

What was HVAC set at?

I've been playing around with different settings to try to figure out how much of the impact is due to heating the cabin vs heating the battery.

I haven't been down to 0F but just as an example - using heated seats for all 4 passengers vs HVAC at 70F (outside temp ~35F) resulted in 2.2mi/Wh vs 1.7mi/Whi at 70mph. With 4 we were all pretty comfortable still with body heat filling the cabin but I'm not sure that's feasible at 0F. Curious nonetheless.

I believe 76F. The heater struggles to keep up at low temps unless you recirculate, then the windows fog up. I had the seat heater on low as well as the steering wheel on.

 

[mindstormsguy]

As others have said, I’d you keep the truck plugged in, and preheat it before leaving, you’ll see *drastically* better efficiency figures than this in the cold.

It’s not so much keeping the vehicle warm that consumes so much power, it’s getting it warm in the first place. These things have hundreds of pounds of battery. It takes a lot of energy to heat that mass up if it’s cold soaked. And until you do heat it up, you’re getting penalized twice. Once because you’re spending energy to heat it, and once because you can’t get as much energy out of it because it’s cold.

 

[bdavis171]

As others have said, I’d you keep the truck plugged in, and preheat it before leaving, you’ll see *drastically* better efficiency figures than this in the cold.

It’s not so much keeping the vehicle warm that consumes so much power, it’s getting it warm in the first place. These things have hundreds of pounds of battery. It takes a lot of energy to heat that mass up if it’s cold soaked. And until you do heat it up, you’re getting penalized twice. Once because you’re spending energy to heat it, and once because you can’t get as much energy out of it because it’s cold.

I preheat at home while plugged in, but it does not pull from the external power if charged to its preset limit. Plugging in isn't an option at work.

 

[Mysta]

Dang. Just over 100 miles on a full charge. We really need a breakthrough in battery tech to handle this.

Well this could be misleading if they had a relatively short trip then it probably spent the whole trip getting battery/cabin to temp then efficiency would shoot up to normal. The best solution (realistically) is for departure schedule. Can use charger to warm up car/battery then the trip will be relatively normal, just a bit low.

 

[mindstormsguy]

I preheat at home while plugged in, but it does not pull from the external power if charged to its preset limit. Plugging in isn't an option at work.

Yeah, I do the exact opposite. I have free charging at work, so I'm generally plugged in at work, and I intentionally stay unplugged at home (gotta take advantage of the free power at work!) It means I get crap efficiency in the morning commute, but it's not an issue for me, since I don't have to go for enough for it to matter.

Re not pulling from the charger to heat, yeah, that's just how it works. I don't know if Tesla is different, but all my EVs have done the same. They pull from the battery, and then only once the battery drops below a certain level does the charger kick in to top it back off. The Rivian seems to have a narrower deadband for how low the battery will go before it starts charging again than my etron has. On the bright side though, this'll help heat the battery.

 

[DJG]

Dang. Just over 100 miles on a full charge. We really need a breakthrough in battery tech to handle this.

Don't go off the deep end based on this data point. Between the short 20 minute drive and HVAC set to 76 degrees (!), this is a data point that absolutely should not be extrapolated to a full range number.

Setting the HVAC to a more reasonable temp (68 or so) and on a longer drive, I would expect efficiency to be higher by at least 25%, if not more.

A tip for everyone, the HVAC is not even necessary at ambient temps above freezing, body heat alone in a pre-heated cabin maintains comfortable temps in the high 60's. I say this based on actual testing with independent bluetooth temperature sensors. It's especially true on a sunny day, subtract a few degrees for overcast conditions.

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