How We See It - Tesla, EVs and the Grid

How We See It - Tesla, EVs and the Grid

Every time Tesla breaks into a new market, the media brings up the same concern: that electric vehicles will overwhelm electric grids, resulting in blackouts. But researchers, analysts, and government officials agree this worry is unfounded.

According to many, including the Federal Energy Regulatory Commission and the Electric Power Research Institute, EVs like the Tesla Roadster and upcoming Model S won’t strain standard electrical grids for several reasons:

EVs don’t use much more power than major electronics. The energy demanded by most plug-in vehicles during charging (about 2 kilowatts) is the same amount drawn by four to five plasma-screen televisions. In just the U.S., 115 million households own televisions, and more than half own two or three -- yet you never hear about consumers and utilities panicking about TVs disrupting the grid. There’s a common misconception that electric cars will double or even triple the amount of power pulled from the grid by the typical home, but this simply isn’t the case.

Electric vehicles will roll out gradually. Analysts predict that only 500,000 EVs will be produced around the world every year, starting in 2015. Continuing with the television comparison, the half million cars added every year to the world’s supply will use about as much power as 2 million plasma TV sets. To put this in context, about 28 million televisions are sold annually in the U.S. alone. Considering that grid utilities are already upgrading local transformers and grid equipment to handle greater loads, accommodating a growing number of EVs shouldn’t be a problem.

Smart grid safeguards are on the way. In addition to adding capacity, utilities are creating incentives and mechanisms to encourage EV charging at night when energy demand is low. Many power companies are planning to introduce discounted rates for EV owners who plug in during off-peak hours. Today, utilities are rolling out millions of residential smart meters and devices that will allow for simple, automated charging. Soon, EV owners will be able to plug in when they get home from work at 5 pm, knowing that their car won’t start charging until cheaper electricity rates kick in at 11 pm. This technology is set to become commonplace well ahead of major EV market share, ensuring a stronger grid for the next wave of transportation.

Tesla is taking grid parameters very seriously as we deliver more cars. The Roadster is designed to consume only as much power as is available. Pair this with the fact that the average Roadster only needs its battery topped off after driving an average of 40 miles a day, and it’s clear that EVs won’t break the grid anytime soon.

Timo | 09. September 2010

Very much agree with Brian H. Good summary but there are a lot of spleling msiateks.

Brian H | 10. September 2010

No spelling mistakes left, just missing spaces, running 2 words together here and there.

As far as the grid etc. goes, update on Focus Fusion: it's possible they will hit "scientific break-even" around the end of this year. Once that hits, the engineering will kick into high gear.

And if/when that succeeds, energy will be (super-)cheap and available everywhere. Forever.

JackB | 12. Oktober 2010

Grid demand would be manageable even if every gasoline vehicle in California instantly became an EV. For 2010, some 14 billion gallons of gasoline will be burned, and some 310 million megawatts will be consumed. Let's assume that real world ICE efficiency, complete with idle losses and traffic jams, is about 15 mpg. An EV could could go about same distance on about 6 kWh of electricity. That means the state's gasoline demand could be replaced with 124 million megawatts of electricity. In theory that's a 40% increase in grid demand, but coincidentally it also takes about 6 kWh of electricity to refine a gallon of gasoline. So it really comes down to what happens to the refineries in the state. Would they be shut down, or reconfigured to sell gasoline to other states and/or emerging countries? Probably a little bit of both. In the end, there might be a 20% increase in electric demand, which would be manageable if most of the demand was off-peak. California is probably worst case, because it has one of the lowest per capita electricity consumption rates and one of the highest per capita gasoline consumption rates. Other states would likely have an easier time with the transition.

Jack Bowers

JackB | 12. Oktober 2010

P.S. I live in Rocklin, a Sacramento suburb served by PG&E. This year we've have 8 major power outages (lasting a total of about 100 hours) due to a fault in an underground 21 kV line that keeps burning up switches. When it comes to threats to grid reliability, perhaps the executives at PG&E should take a hard look at their own infrastructure rather than crying wolf over EVs. | 22. Oktober 2010

Well the way technology is heading the bloombox (or other such inventions) may just well rid us of the grid completely anyway. Roll on self powering homes that do not rely on an unsightly and inefficient grid.

Brian H | 23. Oktober 2010

The bloombox is a glorified large fuel cell. I.e., it requires fuel (a hydrogen source, usually NG.) Very expensive power, all in all.

Check out my link to ; here's the latest official video "Update" on its research project:
It looks like modular 5MW stand-alone generators may start hitting the market in about 5 yrs. That would also eliminate pressure on the grid, but at about 1/20 the cost of current power sources, not 3-5X as much, like the BloomBox.

Talkredius | 14. November 2010

my two cents :

I believe that the main reason for these power grid discussions are commercial reasons, at least here in Germany.
If you install here solar power modules you get a guaranteed amount of money for the supplied electric power for at least 20 years. (you get 0,33 EUR / kWh for the supplied power, the average price for 1kWh is 0,20 EUR at the moment )
So the grid problem could easily be solved with solar power modules, even here, but then the big power suppliers would loose money.
Recently there was a statement from this power suppliers in our press. They try to press the government to cancel this guarantee, because the grid might not handle these power supplies.
( Yes, they meant, that there might be to much supplied power for the grid (!!))
For me a reason more to roll out more EVs :-)

Brian H | 14. November 2010

The reason the German gov't is thinking about cancelling the guarantees is that so many figgered out that it was a "steal", and the costs are immensely greater than the benefits, except for the "stealers".

redsnapper | 22. November 2010

@Tesla: There's still a typo in the opening entry text associated with the link: "Tesla is taking grid parameters very seriously as [it] delivers more cars." :-)

"EV's don't use much more power than major electronics." This seems a little disingenous, coming from Tesla. I don't know about *most* plug-in EV's, but when I charge my Roadster on my 240V-50A circuit, and it draws 40A, that's a 10kW pull - considerably more than 2 or even 3 TV's - make that more like 20 or 30? Indeed, when it's charging, my Roadster draws a bit more power than my central air conditioning. (And in Phoenix, residential A/C is the biggest power consumption in the summer months.) Granted, still, it's only 40A, and I have a 400A service on my house, so *my* utility company has allocated a lot more capacity for my neighborhood and even if everybody on the block had a Tesla Roadster, we'd still manage just fine. But taking into account that sizing of transformers and breaker boxes and so forth is somewhat statistical (i.e., if everybody on the block tried to draw 400A at the same time, we'd probably blow the neighborhood fuse), and that average residential service is probably 200A or lower, I think it's a little naive to assume that the grid would be able to handle an EV in every garage without some adjustments.

ON THE OTHER HAND, in Phoenix in the summer (when energy demand is highest), I think everybody could drive an EV, and if the charging times were staggered appropriately throughout night, nighttime grid power still would be less than peak afternoon grid power. And in winter, I'm pretty sure our peak grid power is very low compared to summer peaks. (They do shift our on-peak hours in winter vs. summer, but the middle of the night is off peak all year round.)

On another tack: An interesting aspect of grid-tied photovoltaic (PV) generation, is that during the daytime, when the PV system is producing power, it feeds energy into the grid, which is consumed locally and thus reduces the overall capacity requirement of the larger grid. As more and more PV systems go online, it might actually reduce the necessity of expanding grid capacity (at least in Phoenix) - a modest incentive for the utilities to encourage residential systems. I had a 5kW system up and running a couple of weeks before I took delivery of my Roadster 2.5 this past August. In effect, I use the grid as my "battery" for the PV system, and then draw that energy back from the grid during the night. (It now appears, summing over the calendar year, that my total PV generation will exceed my total EV consumption, with a little margin.) If everybody was doing this, would the peak grid capacity have to be increased or not? But since utility grids have to be sized for maximum "instantaneous" capacity, I suspect there will always be room for "off peak" EV charging - even if everybody had an EV. It just has to be managed correctly. Bottom line is, I don't disagree with the original conclusion - EV's aren't going to break the grid any time soon, and however gradual the adoption of EV technology may be, if we're paying attention, we'll have time to adjust.

The main thing is, we've *got* to wean ourselves from fossil fuels, and widespread use of EV's is going to accelerate the process. Tesla, avant garde!

Steve | 23. November 2010

redsnapper, I agree both with Tesla's general theme and with the nits you pick. Transformer capacity is a potential problem that I have experienced as I've twice been with a group of Teslas that managed to overheat the transformer and cause the fuse to blow even though we were not exceeding panel ratings.You are right the the Phoenix grid capacity is not likely to be exceeded by charging EVs in the middle of the night, but it might still be a problem for the transformers. The story I have heard is that the utility depends upon the low load at night with cooler temperatures to let the transformer dissipate some of the heat that was built up during the day with the heave A/C load.

Earl and Nagin ... | 23. November 2010

When we upgraded our service from a 100 Amp to 240 Amp entrance to accommodate PV and EV, an inspector had to come out to check on everything and approve the turn-on. I asked him what could prevent the installation and he said "nothing". If there was a problem, he'd simply order the installation of a new transformer at the street.

Steve | 24. November 2010

Indeed, in both instances of overheated transformers that I mentioned in the previous post, PG&E replaced the transformer with a larger one in a matter of a few hours. Of course, the power was out during those hours, which was inconvenient. So the idea is that they need to start proactively installing larger transformers in the prime EV market areas. Coincidentally, there was an article in the San Jose Mercury News on this topic this morning.

Brian H | 24. November 2010

As far as "got to get off fossil fuels", maybe not so much.

Frac gas and associated liquids are in global surplus, and likely to be so for a long time. I've personally never thought too highly of that reason for going electric in cars, etc. I think they're just way smarter, more elegant and efficient, and the zero tailpipe emissions is a big deal.

But "saving the world from Peal Oil collapse" is not on, I'm afraid.

Earl and Nagin ... | 30. November 2010

If frac gas and other liquids are in large supply, they can still be most efficiently used by generating electricity with them and feeding it to the grid. This can then be efficiently transported via the grid to run electric cars, rather than trying to make a new car with a new engine, fuel system, and infrastructure for each one.

Brian H | 30. November 2010

Ugh. My typo: "Peak Oil collapse", not "Peal". ;)

Agreed, though NG has a pretty well developed distribution system for other uses, like heating, too. As far as powering cars, NG is No Good, in my opinion, because it must be pressurized. EV with next-gen batteries will sweep the field!

dsm363 | 30. November 2010

There is liquid natural gas (LNG) that I believe is being looked into powering large trucks at least. I agree though that it's not a good way to go. Especially for cars, EVs are the best.

Alan | 08. Dezember 2010

I have read that a consortium of utility companies, ev charger manufacturers and ev manufacturers has looked at the power supply issue for the growing number ev's. They have determined that if ev's are charged at night (which I do 95% of the time) the existing power generating capacity in the U.S. is capable of charging 150 million ev's when figuring the average charge is for 40 miles. That is because the generating capacity is determined by the demand during the day so there is excess capacity at night. This same article agrees with Steve that the only modifications to the existing distribution system would be to upgrade some transformers in some neighborhoods.
In fact, an argument could be made that the more ev's that charge at night the lower our electrical costs will be because the utility companies will be receiving more revenue per genetating plant and so will be able to distribute the fixed costs out over more Kwh's of production.

Rrroger | 10. Dezember 2010

That sounds like the only good arguement for "smart meters", that can adjust our residencial rates for off peak electric useage, at lower $ rates per KWHr at night!

Samuel H. | 10. Dezember 2010

For natural gas to be liquid, it must have a low temperature and a high pressure. LNG, not a good idea. NG-powered vehicles, however, are an interesting concept. Almost every house has a natural gas line. A gas pump could be installed allowing someone to fill up his car at his own house. Still, NG-powered vehicles are not quiet, and they still produce pollution. I would go electric.

Brian H | 10. Dezember 2010

The best use for NG is to make electricity for EVs. Get a Tesla and an NG generator!

Roblab | 24. Dezember 2010

for California PG&E power co., largest power user is ... wait for it ... refineries. So, as EVs become more popular, and gas demand is lower, and refineries have less demand, guess where the power comes from!
Those transformers have a life span. They get replaced even when you don't blow them out. If you do, they just replace them. Just another day at the power co.
Or, if you're like me, you can run off grid, charge off grid, and who gives a care about transformers burning up.

By the way, I am not filthy rich. I earn nurse wages. I also save my money. Part of it I save in a Sig series reservation account.

bcuddin | 22. März 2011

To preface; I'm a huge fan of Tesla Motors. I think the idea of a company dedicated to electric cars that are actually attractive to the general public. I'm not completely won over by the viability of electric cars just yet. Though this is the best idea I've heard for what seems that is inevitably about to come. Enough of that though. I do have a question about this topic, or more so some offered solutions, if not just temporarily.

"Thin-film" solar panels. Where are they? Where the heck are they? The exceptionally beautiful Model S (stunning),with it's panoramic-viewing glass roof. Impressive, but where's the thin-film photo-voltaic? If the market naysayers say that the electric car will put "extremely high" demand on the grid, and that we aren't ready, then let the cars be the generators themselves. Or fans that were run by solar power, when the car is sitting in traffic, to cut down on wasting the car's electricity?

Thin-film solar panels are apparently very inefficient at this point in time I know. Expected efficiencies at this point are around 19% at their, not excellent. But even Elon Musk worked with one of the highest grade user of thin film photo voltaics; NASA. If we could spend the money with NASA, why not EV's. I love the idea of Tesla Motors, and its potential. Why not a screen that aligns itself to this glass and will be retractable? We have moon-roofs that can do this with glass, where's the investment into Thin-film solar panels?

Talk about killing two birds with one stone. You mean saving the interior of the car from solar degradation AND generating electricity? (not to mention the negligible weight addition) Yes, that simple. You mean selling an electric device with a charger, YES! You want to sell a car that's worth it's buck, sell something that cal pay for itself, or at least try. Isn't this company in California?

The numbers...well, I don't have any. But I do know that the surface area of solar energy that can pass through that glass is immense. Even though inefficient for the time being, it could still manage enough of a slow steady trickle charge that serves as a neat sun visor. I did mention you guys were based in California right? The typical workday is 8 the day. Where do most cars spend their time when not used? In the sunlight!!!, Doing what? Generating heat inside your car. Though a solar-electric car is an extremely hard-sell, the idea of a solar charged electric vehicle is not.

Now, tell me why not? if they don't work, scrap the film panels. Or just not use the idea at all. Imagine if every car had a thin-film solar visor...oh wait. They don't make those...yet. That's a wink to you Tesla.

bcuddin | 22. März 2011

*sorry, couldn't fit everything in there, and there were spelling mistakes. Basically all I'm saying is that I understand the point of view a business must take to make and sell a car, while still making profits. There is a lot of tension in the solar power community. There is a lot of opposition based on its problems with efficiencies. But I believe, I truly believe that this is a good idea. There are ads and "guarantees" on marine-automotive battery chargers, that cover less surface area than what the Model S does. Though there are more batteries in the Tesla, One would assume that solar panels atop a roof are efficient enough over the period of a sunny day to charge some batteries, am I right on that?

dsm363 | 22. März 2011

They probably wouldn't add enough range (maybe a few miles at most over the entire day) to make it worth the costs or complexity. Good idea but don't think it's ready for primetime yet. Maybe a small solar panel to run an interior fan like the Prius may work to cool the car while parked but not to charge the 70+ kWh battery pack.

Timo | 22. März 2011

If you cover entire roof of the car with thin film solar panel and leave it at Sun for 8 hours you get maybe 200W (20% conversion) * 0.5 (for Sun angle) * 1.5 * 1.5 meters (roof) * 8 hours = 1.8kWh. Model S uses roughly 90kWh / 300 miles so 3.33 miles / kWh 1.8 * 3.33 ~= 6 miles in perfect day. 3 miles each way.

Not very useful. You can walk that in about 45 minutes, using bicycle maybe 15 minutes without hurry. If you live that close to your work and are not interested in exercise you should buy electric scooter. Much easier in traffic jams, faster than car in that small distances (no parking problems) and clean (and a lot cheaper than Tesla cars).

Vawlkus | 25. März 2011

Don't forget the expense: PV tech is still costly. I don't have the numbers to back it up, but I believe adding PV to the model s would push the price up another 10 to 20 grand. On a car with a 50 grand base prove, that's one expensive option!

cablechewer | 25. März 2011

I doubt it would be that expensive. I priced a 216 watt PV panel at about US$800 a couple days ago. You would still need some electronics and other components to make it work in addition to that. If you were applying thin film collectors it should be even cheaper. A small panel to run a fan that exhausts hot air from the cabin while the car sits in the sun should be fairly cheap (some common retailers sell them). Applying thin film to a wider area is something I would guess would be priced somewhere in the $1000-$2500 per square meter range if Tesla decided to present it as an option.

Sudre | 26. März 2011

With those numbers it would take more than $3,500 to charge 1000 watts an hour. That is extremely expensive considering I pay 5 cents a kilowatt/hour here in the midwest.

I'd have to use it for over 70,000 hours for it to pay off.
In Missouri I have a 5 hour average useful charging time off solar a day. SO I'd have to use that panel for 35 years before it payed for itself.

I never have seen the cost savings in solar but my electricity is cheap.
It might be a reasonable option for those paying 20-25 cents a kilowatt/hour.

bcuddin | 29. März 2011

Well, see. Maybe I have my numbers incorrect, or other companies are selling their product under false pretenses. For example. If every sq. meter of solar panel has the potential for 1000 Watts at 100% charging efficiency (unrealistic) with thin-film reaching upper limit of 20% efficiency at highest point. So, 1000 Watts * 20% efficient conversion is 200 Watts/hour. If the sun shines 8 hours of the day you work, then you'll charge 8 hours * 200 Watts per square meter of solar panel (thin film) equals 1600 Watts (1.6 Kilowatts) potential per day. You're right, this isn't enough for the 90 Kilowatt hour(300 mile range). But that also assumes that the thin film is relegated to only 1 square meter, I'd assume there is close to 2 or more square meters of potential coverage area. So for the sake of argument, then you'd have 2 * 1.6 Kilowatts = 3.2 Kilowatts. per 8 hour day of sunlight. 3.2 kilowatts * 7 days a week = 22.4 Kilowatts per week. 4 weeks to the month * 22.4 Kilowatts = 89.6 Kilowatts per month. That's almost one third of a full charge meaning it would take you a little over 3 months for a full charge. Fine. You're right there too. But what about pv panels that are installed at home or at businesses which reach 40%(with same measurements) efficiencies on top of that? Also, how much energy(potential electricity) is burned using petroleum to ship petroleum? Meaning, drill the oil, capture it, ship it via boat, refine it and then distribute it using trailer tractors to ship it everywhere. How much oil does it take just to ship oil to its final destination? Where as making electricity in one place and sending it over power lines almost removes the shipping costs after having power produced. I'm not saying that pv's in cars are a solution just yet, but they don't take anything away. Tesla could sell pv's with their cars, you know how some car companies sold gas contracts as a selling point with their cars not too long after the prices jumped to almost $5 per gallon when the refinery in the gulf blew. Generating electricity in one place and sending it over permanent cables doesn't have the costs that maintaining a shipping fleet does, especially when one uses their own product to sell their product. There is always loss. Solar has a strong potential to shut down the argument of causing a disturbance on the grid. Right, if cars started doing that it would. My argument is that if there is free power/energy to be had, especially with how well solar and ev's go together, why the heck not? There is always gain when the energy source is free. ALWAYS.

Timo | 29. März 2011

You should look at Solar City I think Tesla has some connection to them, so maybe you get panels from them a bit cheaper than other places. (

(BTW, it is quite a bit less than 1.6kWh / day for 1m^2 thin film, you need to have your solar panel directed to Sun to get full power, which in case of a car is not the case)

Sudre | 29. März 2011

I'm not saying solar is wrong for everyone. It works for people who have high electric costs. You have to do the math and figure out if it works for you. There are flexible solar panels you can roll up and put in your trunk.

My company installs solar panels.... rarely.

To get the full efficiency out of a solar panel it must be pointed directly at the sun. For max efficiency (that 20% you are talking about) you need to mount the panels on a tracker that will follow the sun.

Dust, pollen, snow, leaves.... anything on the panels will reduce the efficiency.

Clouds will reduce the efficiency.

The sun does not shine at full strength from sunrise to sunset. At rise and set it is coming thru more atmosphere so the efficiency is less. Best efficiency is when the sun is directly over head.

There are less sun hours in winter than in summer.

That's where the AVERAGE usable hours comes from. In St, Louis, MO there are 5 hours of sun per day on average for the year. There are charts and all kinds of stuff on the web to calculate the pay off. In Saint Louis it's just not there yet.

Sun angle calculator:

This one will give you an idea of solar output if you live in the US.

Also watch the solar panel warranties very closely. The site above has good expensive panels. They guarantee the panel to be at 80% in 25 years. Some panels drop in power on a parabolic curve the minute they see sunlight over the 25 year warranty.

Sudre | 29. März 2011

Darn map now shows St. Louis only has 4 hours (or less) now. Well at least they update their web page.

searcher | 04. April 2011

ifilm77, You were posting this same messege on all the threads. As someone pointed out to you not necessry to post same messege on all threads as most of us read them all any way. Some were critsizing you for this. I just thought you might hve not learned the ropes yet and defended you but it was pointed out to me you were likely just advertising you website. Whether just a new kid on the block and not familiar with how things go or someone blantantly advertisising will let you decide. But surely you know now not to put same messege on every thread. I kind of felt ridiculous defending you when it was pointed out why you were posting on all threads. Anyway whatever, glad you like the Tesla's and hope you enjoy an SUV.

Ramon123 | 29. Mai 2011

I have been researching solar panels for several years now - I plan to use them on the house I will build. The prices for solar have come down enormously over the past 2 years. Yesterday I
priced some panels by BP and Canadian Solar and Evergreen, all with 25 year warrantees and guaranteed output. The price for some were less than $1.60 per watt. I estimate that my house will require about a 6K system, or roughly $9,000 for 30 panels.
Use microinverters - they make the installation a snap and remove most of reduced harvest issues, such as clouding, dirty panels, shadowing, etc. The Feds grant $1000 per kilowatt capacity of your system and the tax break can be spread over 3 years, I beleieve.
My site, in NC, averages 5 suns, from 3.8 in the dead of winter to 5.9 in the height of summer. Tracking mechanisms have never been recommmended - they are simply not cost effective, and even less so today with cheaper panels - simply add more panels. they are far, far more reliable than any tracker machinery, which is mechanical and will always break down. You can construct your array so that it can have its elevation adjusted as the seasons change, but the benefits are not that great. Simply point your panels due south and elevate them at an angle equal to 90% minus your latitude. That will maximize yearly energy harvest for a fixed array.

daniel1948 | 14. Juni 2011

I looked at the link for Focus Fusion that Brian H posted a while back in this thread. (I am a newcomer to this forum but have been following Tesla for several years.) The article describes a process that sounded so odd to me that I looked it up on Wikipedia, where it is described as being theoretically possible, but extremely difficult, with several enormous technological hurdles and unlikely to come to fruition any time in the near to moderate future. Among the problems are that a much higher temperature is required and much less energy produced, compared with other fusion reactions.

I see no reason that fusion cannot supply energy at some time in the future, but given how far we are from solving the technological problems, I'm comfortable saying that in my lifetime the only fusion power we're going to have outside of minuscule amounts in the lab is that big yellow fireball that rises up over the horizon every morning.

Brian H | 14. Juni 2011

The wiki article is worth about as much as you paid for it. The temperatures involved in the LPP process occur in minute "plasmoids" which are magnetically self-contained, and last microseconds. That's the key to the process; the fusion bursts are short enough not to require "containment", but powerful enough to generate significant ion and electron flows.

Your confidence is based on inadequate investigation.

Ramon123 | 14. Juni 2011

I have been researching and following solar PV for almost two years
and they have become more efficient and a lot cheaper. Thinfilm
is not what an automaker would likely use and they do not achieve 20% efficiencies. Mono or polychrystaline can achieve close to 20% in commercially available panels. Of course, those stated figures of 20% efficiency are actually exaggerations of what will be obtained in most situations. Expect more like 15 or 16% efficiencies, yielding 300 watts off your 2 square meters. Unfortunately you have made several errors - first you assume that 8 hours of sunlight striking a panel that could yield, realistically, 200 watts (max) would provide 8 times 200 watts. Wrong. The panel rated at 200 watts will only yield that rate for a few minutes per day when the sun is dead overhead, there's no smog, etc. or clouds. All other times the panel will yield less than its maximum. Locales are rated in terms of the number of "suns" they receive, on average, for that date. The sun may actually shine for 12 hours in Arizona, but the number of suns will probably be around 6 or 7. Most locales in the US yield 5 or fewer suns per day during the summer and 3 to 4 per day in the winter months. The number can be obtained from solar irradiance charts and provide data from the past 20 years or so for any locale in the world. The other error you make is asssuming that if a panel produces 200 watts, that the battery will absorb
all 200 watts and none will be lost drawing the power from the
battery , both of which are quite wrong. Expect to lose 25% from the action of putting power into and drawing power out of a battery. And there is yet another error- that 200 watt panel is rated to harvest 200 watts (theoretically, not in actuality) only IF it is pointed directly towards the sun, at all times, which is impossible.
Using this data, for an average day, with 5 suns, expect to harvest not 2000 watthours, but more like 1500, and to lose
25% or 375 watthours, ending up with 1125 watthours per day.
That's enough to travel roughly 4 miles in a Tesla Model S.
And the power is worth 15 cents where I come from. The panels will
probably be a $1000 plus option.

frank_landfield | 06. Juli 2011

i'm getting solar panels on my roof from this will reduce my costs, and help the environment, and future generations. this will cost me nothing.
my monthly electric bill will be less. solar city has a GREAT lease program. i wish everybody would do this. thanks. peace. :-)
tesla roadster owner number 1229

drstockton | 27. Oktober 2011

Powered Highways

Not everyone can afford to buy a 300 mile range battery pack; even if prices come down more than current forecasts, there is an environmental penalty associated with batteries of that capacity. Even worse, when EVs become more than a few percent of total vehicles, the queuing of people and vehicles at roadside charging stations on major highway routes will become an intractable problem. What we need is powered highways that sustain the vehicle charge while underway. The vehicle enters the highway with a particular state of charge, drives a few hundred miles, or even more, then leaves the powered highway with the same or better charge status. While there are challenges in bringing this to fruition, the problems are amenable to engineering.

First, the vehicle needs a computer-controlled pickup arm that optimizes the charge efficiency over the uneven roadway and various driver maneuvers. Equipped with IR, sonar or radar, the intelligent pick up arm will be articulated and powered to maintain the closest possible alignment of the vehicle to the charge element in the roadway. When you consider what Google is doing with self-driving cars, the knowledge base for vehicular software is getting quite mature.

Second, the charge element in the roadway is also a communications carrier; signals are exchanged between the vehicle and a regional traffic control system that integrates each vehicle into an intelligent grid of all the vehicles active on that roadway. Auto-pilot ervices are provided to the driver that surpass what can be provided by cruise control, including possible hands-free driving. The auto-pilot system provides control over the vehicle while it is in the charging lane and controls its relationship to other vehicles in the lane for greatly increased safety. Like the HOV lanes of today, legislation would provide that only EVs could drive in the charging lane. Because the charging element is recessed into the roadway, drivers enter and leave the charging lane at will, just by steering across the lane. The system acquires or releases vehicle telemetry and control automatically. Part of the telemetry system functions will be to steer the vehicle under computer control to also optimize the efficiency of the charging functions.

Third, the vehicle computer provides for payment of the charging toll; use of the charging lane should be something that can be paid in advance for regular users of a particular highway or paid on the spot by "guest" drivers. The tolls should be enough to pay for the electricity used and to retire the capital invested in the charging and computing infrastructure in the roadway. This toll should be favorable when contrasted to the cost of fuel over the same route for a gasoline powered vehicle. For example, I-5 between Sacramento and Los Angeles passes about 105,000 vehicles an hour at peak. If EVs become 3% of vehicles on this route, each one paying about $40 for a 400 mile trip, the peak revenue/hour could be $3,150. The average daily revenue could be in the range of $25,200 and the annual revenue could be over $9 million, or about $100 MM over the life of the infrastructure. At 10% penetration of EVs on a powered highway the annual revenue could hit $30 MM and the lifetime revenue would be over $2 billion.

VolkerP | 07. November 2011


nice thoughts. Allow me to make some comments on that.

First, a mechanical (conductive) energy pickup is improbable. You don't want voltage carrying metal strips exposed on the tarmac. There is, however, an overhead pickup system well established for vehicle use. It's called electric train ;-)
Seriously, inductive electric charge transfer while-you-drive is in test. Engineering problem solved. Now we need funding...

Second, you want only one communication system in the car and you want it to work everywhere, side roads, city, front yard. It will be wireless. Model S will come with 3G or 4G and an attractively priced data plan.

Third, infrastructure projects paid by future users always run into the chicken-egg-problem: Huge investments prohibit a large-scale roll out, low user numbers prohibit a quick scale up, low coverage prohibits many cars to be fitted with the necessary pickup tech.
Some people won't like charge-per-use since it gives an exact record of whodunnitwhereandwhen.
Since electricity cost is 6c per mile, there is little room for margin to run that business model on. Double it and collect another 6c for every mile...
I'm afraid you need the government to step in there, a no-go for so many US citizens... but might be a possibility in China where the govt sticks at nothing.

Brian H | 08. November 2011

At local rates here, home charging costs about 2¢/mi. 10¢ for the privilege of charging on the road is a bit rich!

evanstumpges | 14. August 2012

As someone who spent the last two years of my life designing and building a competition solar car for Iowa State University, I can attest that unfortunately even with the best mono-crystalline silicon solar cells on the market right now, a Model S roof covered in solar panels wouldn't make much of a dent in the overall energy usage of the vehicle. This is not to say that it doesn't make sense to offer it as an option. After all, vehicle's do spend a lot of their lives parked in sunny spots, so why not take advantage of this as much as possible if you can afford the cost?

First a little background. Our 2012 solar car called Hyperion had 6m^2 photovoltaic area using 22.3% efficient cells made by SunPower in California. This is far more area than would be practical for any production vehicle (it barely leaves room for the small cockpit that accommodates a single driver). On a good sunny day with the sun directly overhead, our solar array could produce 1200-1300W. However, over the course of the year in typical Iowa weather, the flat array would only produce an average of 5kWh per day throughout the course of the year assuming that it is never shaded. This is sufficient energy to take the car about 170 per day at a cruising speed of 45MPH. However, the car only weights 660lb with a driver and have an aerodynamic cd of about 0.11. If you'd like more info on the car, check out the fact sheet.

Transferring this solar technology to something like the Model S is certainly possible, but the results would be much less impressive. A quick calculation shows that there is about 1.65m^2 of space available on the Model S roof for a photovoltaic surface. Taking SunPower's latest and greatest C65 cells, this would yield about 350W of power on good day with the sun directly overhead. Again taking Iowa's average solar radiation for a flat panel solar array, this could realistically produce 1.3kWh/day if it weren't shaded. If we assume the Model S can go 3mi/kWh, that would yield a range of nearly 4 miles per day on power from the rooftop solar installation. For the average american that drives 37 miles per day, this would be over 10% of their driving powered on solar energy produced by the vehicle. This could of course be supplemented by an additional home solar installation. In general, a home solar installation makes more sense it me since you could get by with cheaper, lower efficiency solar cells since there is generally a lot more space available on a roof or in a back yard than on a vehicle.

Finally, let's try to gauge the cost of the solar installation described above for the Model S. For our 6m^2 solar car array at Iowa State, we paid $9,000 just for the cells. Hence a Model S installation, the cost of these same cells would be under $2,500. Granted, this cost would likely be a lot lower for mass production due to economies of scale, but then you have to add the cost of the inverter, wiring, and cell mounting/protection. I should mention that there are solar cells on the market that cost significantly less per watt (1/4 the cost), but only have an efficiency of 18-20% and from less reputable companies. My numbers above are intended to show the best case scenario that could be realistically achieved with today's technology (without considering 30% efficient space grade gallium arsenide solar cells which are triple junction and cost astronomically more than silicon solar cells).

Brian H | 14. August 2012

Compared to the cost of slightly increased battery capacity, and the electricity required to fill it, solar on cars is insanely expensive, and in practice almost useless. The constraints do not conform in any respect to how people actually use cars.

Timo | 14. August 2012

There is a one use which could be enough for adding tiny solar panel in practical family BEV: all batteries lose energy slowly if left unplugged, so add a solar panel that just big enough to counter that loss + a bit extra and you can leave your BEV in sunny parking lot indefinitely without plugging it in. For that use panel needed would be tiny.

As option of course, here in Finland such solar panel would not make much sense, but if you live in some very sunny place it could be worth the extra buck.

Brian H | 14. August 2012

Apparently the Karma solar roof cost $5K (or $5K/W?), enough to run a fan. Is that worth it?

Timo | 15. August 2012

That price has quite a bit "Karma" in it, you can run a fan with panel that costs fifty bucks, not five grand if that is all that it is doing.

Real question here is how much power do you need to maintain battery charge.

... found this "50 percent charge would approach full discharge only after about 12 months.

12 months is about 8600 hours, 50% of charge of 85kWh battery is 42.5kWh. 42500/8600 ~= 5W. Not kW, W. to maintain charge panel needed would be really tiny.

Vawlkus | 15. August 2012

Nice to have some hard numbers Evan, thank you.

David70 | 15. August 2012


"Real question here is how much power do you need to maintain battery charge"

And battery temperature.

Brian H | 15. August 2012

Averaged over 24 hrs., say 120Wh, of course, with variable sun hours, intensity, and angle daily, and seasonally. Or none if it's indoors. And assuming it doesn't accumulate a layer of dust or condensed smog. /:p