*Note to move-happy moderators: This is indeed specific to Model 3, I have no idea how S/X/Leaf/e-tron behave in comparison.*

First, I will admittedly use the term "evidence" loosely as this is not a court of law, but a summary of what I've logged myself, what others have observed, what Tesla has stated, and what data summaries can be made by third parties.

I was spurred to do these projections based on a recent surprising experience with leaving my Model 3 out in the cold. This is going to become more common as more people adopt EVs.

My province aims to ban sales of fossil fuel vehicles by 2040. Many people will end up having to park EVs outside in the cold because they don't have a warm garage for many reasons. The current demographic for new EVs are those with a fair amount of money (they're expensive new cars), so they tend to be garage-kept more than the average vehicle. Additionally, the North American capital of EVs (California) doesn't really deal with this "cold" thing as much as others will.

**So, mission statement: We**especially to inform the oncoming common adoption of EVs.

*need*to better understand the energy and financial impacts of having EVs outside in the cold,**The tl;dr Summary**

Results were estimated for somewhere with 4 seasons where some of the year is below freezing temperatures, and the car is parked outside. Results also assume relatively tame highway speeds; if you go on 70+mph highways often, these numbers are too optimistic.

**Light 4-season commuters**should expect to use

**161% more energy**than is implied by the range of the Model 3. That's not 161% compared to baseline, that's an

*additional*161% over the 150Wh/km or so that's advertised.

**Heavy 4-season commuters**should expect to use

**44% more energy**. This is lower mainly because fixed losses (vampire drain, preconditioning) make up a smaller amount of the total energy used.

Even

**light commuters in year-round optimal temperatures**should expect to use

**56% more energy**, just due to a median standby loss per day.

The various factors are expanded on below if you'd like to understand how I got these numbers.

**The Details and Projections**

For the following, I'll be assuming 4 months of the year you'll be in "cold", and 8 months "warm". I have to assume something, and I'd rather assume what is realistic for many people with 4 seasons.

I'll therefore give 122 days to the cold, and 244 to warm. That makes it a leap year, but simplifies the numbers for me.

I'll take "cold" temperatures as a 30% average loss. In my experience and what I've seen from others, cold temp impacts are about 20% at 10C (50F), 30% at 0C (32F), and 40% at -10C (14F) and colder.

I'll assume "warm" losses to be 0%. I personally can do better than the EPA rating in summer at highway speeds using the air conditioning, but if you travel on fast freeways this may be a bad number to use. This is in line with the experience of others as well.

For "rated kilometres", I'll be using 150Wh/km. This corresponds to the rating line on our Model 3 (LR AWD). It might be off by a little bit from the true rating, but the general results won't be far off.

**Case 1: Short-hop Commuter**

Let's say you travel 5,000mi/year (8,047km). This is indicative of someone who doesn't drive very far for work, and makes a few trips that are still relatively local. This is about 40% less than the average American usage.

**Driving: 1,336 kWh**

1,250mi will be in the cold at 30% loss, meaning 1,786 "rated miles" consumed. The rest will be 3,750mi, but with no average loss.

The total consumed only by driving is therefore 5,536 rated miles, or 8,909 rated kilometres. This corresponds to about 1336kWh.

**Standby: 1,057 kWh**

Unlike a gas vehicle, your Model 3 will lose "fuel" when parked.

Tesla states that 1% per day is normal. Most people self-report around 2% per day. In energy numbers from the Stats app, the median appears to be about 1.33kWh every 24h (that's 1.8% for an LR, 2.6% for an SR+).

In the cold, Tesla support claimed you can lose 25km per 12h period in sub-zero temperatures. This equates to

**7.5kWh per 24h period**. That is 10.1% on a LR pack, and a whopping 14.5% on a SR+ pack.

I personally experienced a 6kWh loss per 24h period in -5C (23F), so Tesla's numbers seem a bit off (likely to give them room for excuse-ability). I'll use 6kWh for the rest of my projections (8.1% of LR, 11.6% of SR+).

122 days in the cold at 6kWh/day is

*732kWh*.

244 days in warm temps with a median 1.33kWh/day loss for a total of 325kWh on the warm days.

**Preconditioning: 128 kWh**

You didn't get such an expensive car so you could freeze. Let's preheat that thing!

I'll be very conservative and assume a 5 minute precondition. For 122 cold days of the year, the heat runs once per day at its max of 6kW for 2 minutes for a total of 0.2kWh/day, but for another 3 minutes at 2kW for another 0.1kWh and a total of 5 minutes.

Recent updates cause the car to preheat the battery as well. I've seen various numbers for this, but it seems to use about 9kW on an AWD model (the motors are used for heating the battery). Over 5 minutes, this will pull 0.75kWh but give you some more regen ability.

Over the 5 minutes, it cost 0.3kWh for the cabin and 0.75kWh for the battery for a total of 1.05kWh per day, or 128kWh for the cold days of the year.

*Note*: I find the battery heating fairly egregious. It's not necessary, since it

*only*does it if you warm the car from the app. It does not do this if you hop in the car and turn the heat on. The assumption is that this provides extra regen (or regen at all if it's too cold), but it costs way too much energy just to enable one-pedal driving. This would be about 36kWh without the battery heating. Nuts.

**Total and Charging Losses: 3,151 kWh**

**(161% extra)**Summing up the above, we get

*2,521 kWh*for the year, to travel 5,000 mi or 8,047 km.

This works out to 16,807 "rated kilometres", or an

**extra 109%**before charging losses.

You don't use the car much so you probably are just charging off of a standard 120V outlet (in North America, sorry). This only delivers about 80% of what comes out of the wall to your battery due to fixed overheads while charging.

The 2,521 kWh needed by the car thus requires

*3,151 kWh*, working out to 21,008 "rated kilometers" (13,054 "rated miles").

Being a short-distance commuter with a Model 3 in a place with 4 seasons thus costs you

**an extra 161% in energy**compared to simply advertised EPA figures (e.g. 150Wh/km).

*Yikes*.

**Case 2: Long-distance commuter**

Let's say you travel 22,000 mi/year (35,405km). This is indicative of someone like us! My wife travels 120km for work every day, and we use this car for everything else including some longer distance road trips.

**Driving: 6,070 kWh**

7,333mi will be in the cold at 30% loss, meaning 10,476 "rated miles" consumed. The rest will be 14,667mi, but with no average loss.

The total consumed only by driving is therefore 25,143 rated miles, or 40,464 rated kilometres. This works out to about 6,070 kWh.

**Standby: 1,057 kWh**

Same as the

*Short-hop*case above.

**Preconditioning: 128 kWh**

Same as the

*Short-hop*case above.

**Total and Charging Losses: 7,637 kWh**

**(43.8% extra)**Summing up the above, we get

*7,255 kWh*for the year, to travel 22,000 mi or 35,405 km.

This works out to 48,367 "rated kilometres", or an

**extra 36.6%**before charging losses.

Since you use the battery more, you probably have a Level 2 charging setup. This woiuld result in less charging overhead losses, with about 95% of the energy coming out of the wall making it into your battery.

The 7,255 kWh needed by the car thus requires

*7,637 kWh*, working out to 50,912 "rated kilometers" (31,635 "rated miles").

Being a heavy commuter with a Model 3 in a place with 4 seasons cost you

**an extra 43.8% in energy**compared to simply advertised figures.

This is much better than the short-hop case, but still significant.

**Case 3: Short-hop commuter, but always warm**

Want to just see the impact of vampire loss?

Again, let's say you travel 5,000mi/year (8,047km) as a light commuter and never use preconditioning (not even to cool the car off) because you're a trooper and will just vent via the windows if it's hot.

**Driving: 1,207 kWh**

All 5,000mi (8,047km) are assumed to be at 0%, 0% gain, for an effective 5,000mi consumed. This equates to about 1,207kWh.

**Standby: 487 kWh**

We'll take the median from the Stats app, about 1.33kWh every 24h (that's 1.8% for an LR, 2.6% for an SR+). I expect this is a very good representation of warmer climates, as most EVs tend to be in those right now.

366 days in warm temps with a median 1.33kWh/day loss for a total of 487kWh over the leap year.

**Total and Charging Losses: 1,882 kWh**

**(55.9% extra)**I'm going to assume 90% efficient L2 charging. This implies a lower power available either by standard outlets or lower power public chargers you may use while at work, since you're in such a warm EV-friendly area.

Summing standby and driving usage gives us 1,694kWh, and at 90% charging efficiency you'll need to pull 1,882kWh out of the wall.

This means your 5,000mi traveled (8,047km) actually requires 7,796 rated miles (12,547 rated kilometres) of energy, meaning it takes an extra 55.9% energy than expected for the year.

**Takeaways & Commentary**

This actually blew my mind a bit, and I'm a bit disappointed. I had previously thought that EVs were best for short-hop city commuters, but that's potentially not the case with all the fixed losses going on. By comparison, my gas vehicles historically all used roughly 20% more fuel in winter, including "preconditiong" by idling for a few minutes prior to driving away.

Something I find particularly interesting is the potential impact on cycle count. Elon expects Model 3 batteries to last 1500 cycles. The above impacts for a short-hop commuter imply that only 590 effective cycles would contribute to moving the car (the rest of the energy being used in the losses discussed above). For an SR+, that means instead of an expected 300,000mi (482,000km) it would only go about 118,110mi (190,080km). This is just 18,110mi beyond the battery warranty.

Why haven't we noticed this though? Probably because most of us are plugging in all the time and not meticulously looking into home charging energy (if you even have those stats available).

**The standby losses are well under a dollar per night**, and not something many people would care about when looking at that scale.

**It only looks so bad once you compare it to what your expected energy usage**

*should*have been when looking at a 150Wh/km EPA rating.**Numerical Takeaways:**

- Assume about 500kWh is burned every year just parking in optimal conditions.
- Assume about 1000kWh (double) instead if you have a winter season.
- Very roughly, standby usage is equivalent to about 7000km or 4250mi in an area with a Winter season.
- Median standby usage is equivalent to about 55W in optimal conditions.
- The average American commuter (13,5000mi/year or so) should double their energy usage estimates if going by the EPA rating in colder areas (i.e. A full 325mi charge will ultimately require 650mi equivalent EPA rating energy from the wall)

If you read this far, please let me know your thoughts! I'd especially hope to be insanely wrong on some of the above numbers. I hope it's helpful to people in the future for planning out cost of ownership. And hopefully these standby usages are less as EV tech progresses.

Last edited: Mar 5, 2020