Every time when there is a discussion about the future of superchargers and how they will cope with increasing number of Teslas, a few people jump in and say more stations will be built and it will be just fine. But when you think about the details that doesn't make sense. There is no way adding more stations can prevent extreme wait times. I'll explain why.
In 2013, 18.195 Model S were sold in the US. In first 5 months of 2014, 6800 have been sold (source) which gives a year-end expected sales number of 6800/5*12= 16.320. Let's be modest and assume Model S sales will be 16.000 per year for the following few years; Model X will sell 16.000 units from 2015 on and Gen 3 will sell only 50.000 units in 2018 and later.
Using these numbers, sales in the US would be like this for each year:
2012: 02.558 (Model S)
2013: 18.195 (Model S)
2014: 16.320 (Model S)
2015: 32.000 (16.000 Model S + 16.000 Model X)
2016: 32.000 (16.000 Model S + 16.000 Model X)
2017: 32.000 (16.000 Model S + 16.000 Model X)
2018: 82.000 (16.000 Model S + 16.000 Model X + 50.000 Gen3)
2019: 82.000 (16.000 Model S + 16.000 Model X + 50.000 Gen3)
Total number of Teslas in the US would be as follows at the end of each year:
2012: 002.558
2013: 020.753 (2.558+18.195)
2014: 037.073 (2.558+18.195+16.320)
2015: 069.073 (2.558+18.195+16.320+32.000)
2016: 101.073 (2.558+18.195+16.320+32.000+32.000)
2017: 133.073 (2.558+18.195+16.320+32.000+32.000+32.000)
2018: 215.073 (2.558+18.195+16.320+32.000+32.000+32.000+82.000)
2019: 297.073 (2.558+18.195+16.320+32.000+32.000+32.000+82.000+82.000)
As you can see, at the end of 2019, number of Teslas in the US will be more than 10 times of what it is now. Currently there are 27.553 Model S in the US (2.558+18.195+6.800=27.553). I can hear the same people saying, "Superchargers will be 10 times more too." OK, let's assume they will be.
Number of stalls per station is limited by two factors: available parking space and capacity of electrical infrastructure. In the UK Tesla and Ecotricity are already fighting each other for the same rest stop locations because in some locations Ecotricity can't even add more of their own stations because power capacity is limited. They don't want Tesla to come in and kick them out. Of course parking space is limited too. Because of these two limits number of stalls per station can't go over 10 stalls on average. Currently there are only two locations with 10 stalls. Most locations have 8 or less. At http://supercharge.info you can click on 'Data' and sort by stalls.
Certainly it would be nice if Tesla could expand an existing station from 10 stalls to 100 or 50 or 20 but that's not going to happen for almost any existing station. Therefore Tesla needs to increase number of stations. Some might say, "That's not a problem. They will just spread them equally every 20 to 40 miles along the highways like gas stations." But can they?
The distance between Los Angeles and Las Vegas is a fixed number that doesn't change. The range of the cars is more or less the same. Variables like elevation and weather will have the same effect on all cars driving in the same direction on the same day between the same two cities. When you leave a city you typically don't need to charge too soon because you will leave with a charged battery. Even if you wanted to charge soon after leaving a city it wouldn't make sense because charging a battery that is somewhat full takes more time and charging too early won't give you enough range to get you to your destination.
What is going to happen is, in 2020 there will be up to 10 stations between LA and Vegas on a 100 mile stretch in the middle. "So what's the problem?" some might say. "The probability of drivers picking one station or another is the same, isn't it?" Even if there is some randomness, does this mean some stations could be packed while others are half empty? We don't see this happening with gas stations (except maybe when they have a discount price).
But I think gas stations and supercharge stations are very different for two reasons: Firstly if you arrive at a gas station that has 10 pumps and there are 20 cars, it is not a big problem. You will only wait maybe 5 minutes. If the same were to happen at a supercharger you would wait 45 minutes before you start charging. Secondly, if for some reason gas station is too crowded (maybe because of discount price or some pumps not working or some special event in the area), an ICE driver could just drive to the next station. At a supercharger this is not easy because you have already driven away from the main highway, you might not have enough range and even if you have it is not guaranteed the next supercharge station won't be even more crowded.
Here is another way to visualize the problem. Imagine there is a group of 15 people on the street. There are a bunch of restaurants in front of them. The reason I like the restaurant example is because the time you spend there is comparable to a supercharge time. Therefore comparing superchargers to restaurants makes more sense than comparing them to gas stations.
Each restaurants has 10 chairs and they are all empty. The diners can pick any restaurant they want but once they are in, they can't switch. Because number of people is not too high compared to the capacity of each restaurant, statistically it is unlikely that more than 10 people will go to the same restaurant. It might happen but it will be uncommon. And when it rarely happens there will be 11 or maybe 12 people and the wait time won't be too long for most of the diners.
Now let's multiply number of diners by 10. Now we have 150 diners on the street waiting to go to a restaurant but each restaurant can only have 10 diners (because as you remember we couldn't increase number of stalls). Even though now there are lots of restaurants, because the number of diners is so high, it is now very likely that some restaurants will have 20, 30 or maybe more guests while others have none or few.
As you see increasing number of stations doesn't work even if you increase them at the same rate as number of cars. If Tesla was building superchargers on their own land with enough empty space to add lots more stalls over time then this problem wouldn't happen.
Update: Here is another analogy:
Imagine an office worked sitting on a desk and processing documents. She can process 10 documents in 40 minutes, representing a station with 10 stalls. There is a steady stream of 10 customers per 40 minutes. Demand and capacity is an exact match. Customers put the documents on the desk and leave.
Now let's double the demand from 10 customers to 20 per 40 minutes. We need to double the capacity too but unfortunately we can't make the office worker process more documents (replicating 10 stall limit). Instead we add another desks and office worker.
When people arrive they have to leave their documents on one of the desks without knowing the workload. This replicates the fact that you don't know how crowded a station is before you arrive there. Because the randomness of choice sometimes one desk or the other will be overloaded.
Now image demand would increase 10 times instead 2 and there would be 10 desks. The possibility that some of desks will be overloaded a few times their capacity is high.
Around 2019, 30 Teslas waiting to charge at a 10 stall station is likely to happen if things were left alone. But given that there are so many smart people at Tesla, they must be thinking about these things already. Here are some possible solutions that Tesla might use, although each have a downside.
1. Smart Navigation: In one of the meetings, could be Amsterdam or Oslo, Elon said in the future you will never have to worry about superchargers. He said you will enter your destination and the navigation will pick the supercharger for you. To me this means a central computer will monitor empty stalls in all superchargers. It will then make a calculation based on your current location, distance to different stations, your speed, your remaining range. Then it will assign each car to a different station.
I think this should work fine but if all Teslas don't have a 3G connection in the future, it can't work. Also it can't work if superchargers are shared with another car maker.
Update: dsm363 said with the Gen3 Tesla might offer free 3G for life that comes without web functions. I think that sounds like a great idea.
2. Digital road signs: Because you have to divert from the highway to go to a supercharger, you don't want to go there just to find out it is extremely crowded. So if there were digital road signs on the highway that show available space for upcoming stations like "Tesla supercharging 1 mile, available stalls 3", then you could decide whether to skip or take it.
One problem with this is, if the distance from the sign to the station is too long, it could be full by the time you arrive there. Because if it shows 1 available space and somebody takes the turn from the highway, until that car arrives at the station the sign will continue displaying 1. But during that time other cars might also decide to go there. The further away from the highway, the worse the stations will be.
Update: Zextraterrestrial said the information would be on the screen in the car instead on road signs. I think it is possible. This would be an earlier version of the smart navigation. I think before there is smart navigation it is more like to have real time availability data on the screen. So I think I was wrong with the road signs idea. On screen data is more likely. So here the new version of #2:
2. Real-time availability data: On the 17" screen you will be able to see how many stalls are available in each station.
3. On-road stations: What would be great are charging stations on pit stop lanes parallel to the main road. Of course at highway speeds you can't look and decide whether you want to stop there. So digital road signs still need be placed before these stations. But because the stations are so close to the signs, there is no risk of arriving there and finding the space occupied.
The problem with these is, they are not great places to spend time. You are stuck in your car and there are no facilities around. It is also a bit of a security risk and you still need to stop at a restaurant and restroom.
4. Mega Stations: At critical locations such as LA to Vegas where a single station in the middle would be sufficient, Tesla could build mega stations that have empty space to expand to 50 or 100 stalls over time. I think the current biggest station is in Norway with 48 spaces. It is non-Tesla of course.
(Thanks to RubberToe for reminding me of this option).
In 2013, 18.195 Model S were sold in the US. In first 5 months of 2014, 6800 have been sold (source) which gives a year-end expected sales number of 6800/5*12= 16.320. Let's be modest and assume Model S sales will be 16.000 per year for the following few years; Model X will sell 16.000 units from 2015 on and Gen 3 will sell only 50.000 units in 2018 and later.
Using these numbers, sales in the US would be like this for each year:
2012: 02.558 (Model S)
2013: 18.195 (Model S)
2014: 16.320 (Model S)
2015: 32.000 (16.000 Model S + 16.000 Model X)
2016: 32.000 (16.000 Model S + 16.000 Model X)
2017: 32.000 (16.000 Model S + 16.000 Model X)
2018: 82.000 (16.000 Model S + 16.000 Model X + 50.000 Gen3)
2019: 82.000 (16.000 Model S + 16.000 Model X + 50.000 Gen3)
Total number of Teslas in the US would be as follows at the end of each year:
2012: 002.558
2013: 020.753 (2.558+18.195)
2014: 037.073 (2.558+18.195+16.320)
2015: 069.073 (2.558+18.195+16.320+32.000)
2016: 101.073 (2.558+18.195+16.320+32.000+32.000)
2017: 133.073 (2.558+18.195+16.320+32.000+32.000+32.000)
2018: 215.073 (2.558+18.195+16.320+32.000+32.000+32.000+82.000)
2019: 297.073 (2.558+18.195+16.320+32.000+32.000+32.000+82.000+82.000)
As you can see, at the end of 2019, number of Teslas in the US will be more than 10 times of what it is now. Currently there are 27.553 Model S in the US (2.558+18.195+6.800=27.553). I can hear the same people saying, "Superchargers will be 10 times more too." OK, let's assume they will be.
Number of stalls per station is limited by two factors: available parking space and capacity of electrical infrastructure. In the UK Tesla and Ecotricity are already fighting each other for the same rest stop locations because in some locations Ecotricity can't even add more of their own stations because power capacity is limited. They don't want Tesla to come in and kick them out. Of course parking space is limited too. Because of these two limits number of stalls per station can't go over 10 stalls on average. Currently there are only two locations with 10 stalls. Most locations have 8 or less. At http://supercharge.info you can click on 'Data' and sort by stalls.
Certainly it would be nice if Tesla could expand an existing station from 10 stalls to 100 or 50 or 20 but that's not going to happen for almost any existing station. Therefore Tesla needs to increase number of stations. Some might say, "That's not a problem. They will just spread them equally every 20 to 40 miles along the highways like gas stations." But can they?
The distance between Los Angeles and Las Vegas is a fixed number that doesn't change. The range of the cars is more or less the same. Variables like elevation and weather will have the same effect on all cars driving in the same direction on the same day between the same two cities. When you leave a city you typically don't need to charge too soon because you will leave with a charged battery. Even if you wanted to charge soon after leaving a city it wouldn't make sense because charging a battery that is somewhat full takes more time and charging too early won't give you enough range to get you to your destination.
What is going to happen is, in 2020 there will be up to 10 stations between LA and Vegas on a 100 mile stretch in the middle. "So what's the problem?" some might say. "The probability of drivers picking one station or another is the same, isn't it?" Even if there is some randomness, does this mean some stations could be packed while others are half empty? We don't see this happening with gas stations (except maybe when they have a discount price).
But I think gas stations and supercharge stations are very different for two reasons: Firstly if you arrive at a gas station that has 10 pumps and there are 20 cars, it is not a big problem. You will only wait maybe 5 minutes. If the same were to happen at a supercharger you would wait 45 minutes before you start charging. Secondly, if for some reason gas station is too crowded (maybe because of discount price or some pumps not working or some special event in the area), an ICE driver could just drive to the next station. At a supercharger this is not easy because you have already driven away from the main highway, you might not have enough range and even if you have it is not guaranteed the next supercharge station won't be even more crowded.
Here is another way to visualize the problem. Imagine there is a group of 15 people on the street. There are a bunch of restaurants in front of them. The reason I like the restaurant example is because the time you spend there is comparable to a supercharge time. Therefore comparing superchargers to restaurants makes more sense than comparing them to gas stations.
Each restaurants has 10 chairs and they are all empty. The diners can pick any restaurant they want but once they are in, they can't switch. Because number of people is not too high compared to the capacity of each restaurant, statistically it is unlikely that more than 10 people will go to the same restaurant. It might happen but it will be uncommon. And when it rarely happens there will be 11 or maybe 12 people and the wait time won't be too long for most of the diners.
Now let's multiply number of diners by 10. Now we have 150 diners on the street waiting to go to a restaurant but each restaurant can only have 10 diners (because as you remember we couldn't increase number of stalls). Even though now there are lots of restaurants, because the number of diners is so high, it is now very likely that some restaurants will have 20, 30 or maybe more guests while others have none or few.
As you see increasing number of stations doesn't work even if you increase them at the same rate as number of cars. If Tesla was building superchargers on their own land with enough empty space to add lots more stalls over time then this problem wouldn't happen.
Update: Here is another analogy:
Imagine an office worked sitting on a desk and processing documents. She can process 10 documents in 40 minutes, representing a station with 10 stalls. There is a steady stream of 10 customers per 40 minutes. Demand and capacity is an exact match. Customers put the documents on the desk and leave.
Now let's double the demand from 10 customers to 20 per 40 minutes. We need to double the capacity too but unfortunately we can't make the office worker process more documents (replicating 10 stall limit). Instead we add another desks and office worker.
When people arrive they have to leave their documents on one of the desks without knowing the workload. This replicates the fact that you don't know how crowded a station is before you arrive there. Because the randomness of choice sometimes one desk or the other will be overloaded.
Now image demand would increase 10 times instead 2 and there would be 10 desks. The possibility that some of desks will be overloaded a few times their capacity is high.
Around 2019, 30 Teslas waiting to charge at a 10 stall station is likely to happen if things were left alone. But given that there are so many smart people at Tesla, they must be thinking about these things already. Here are some possible solutions that Tesla might use, although each have a downside.
1. Smart Navigation: In one of the meetings, could be Amsterdam or Oslo, Elon said in the future you will never have to worry about superchargers. He said you will enter your destination and the navigation will pick the supercharger for you. To me this means a central computer will monitor empty stalls in all superchargers. It will then make a calculation based on your current location, distance to different stations, your speed, your remaining range. Then it will assign each car to a different station.
I think this should work fine but if all Teslas don't have a 3G connection in the future, it can't work. Also it can't work if superchargers are shared with another car maker.
Update: dsm363 said with the Gen3 Tesla might offer free 3G for life that comes without web functions. I think that sounds like a great idea.
2. Digital road signs: Because you have to divert from the highway to go to a supercharger, you don't want to go there just to find out it is extremely crowded. So if there were digital road signs on the highway that show available space for upcoming stations like "Tesla supercharging 1 mile, available stalls 3", then you could decide whether to skip or take it.
One problem with this is, if the distance from the sign to the station is too long, it could be full by the time you arrive there. Because if it shows 1 available space and somebody takes the turn from the highway, until that car arrives at the station the sign will continue displaying 1. But during that time other cars might also decide to go there. The further away from the highway, the worse the stations will be.
Update: Zextraterrestrial said the information would be on the screen in the car instead on road signs. I think it is possible. This would be an earlier version of the smart navigation. I think before there is smart navigation it is more like to have real time availability data on the screen. So I think I was wrong with the road signs idea. On screen data is more likely. So here the new version of #2:
2. Real-time availability data: On the 17" screen you will be able to see how many stalls are available in each station.
3. On-road stations: What would be great are charging stations on pit stop lanes parallel to the main road. Of course at highway speeds you can't look and decide whether you want to stop there. So digital road signs still need be placed before these stations. But because the stations are so close to the signs, there is no risk of arriving there and finding the space occupied.
The problem with these is, they are not great places to spend time. You are stuck in your car and there are no facilities around. It is also a bit of a security risk and you still need to stop at a restaurant and restroom.
4. Mega Stations: At critical locations such as LA to Vegas where a single station in the middle would be sufficient, Tesla could build mega stations that have empty space to expand to 50 or 100 stalls over time. I think the current biggest station is in Norway with 48 spaces. It is non-Tesla of course.
(Thanks to RubberToe for reminding me of this option).
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