Is the Tesla Model S an electricity guzzler? One driver trying to answer that question says it does gobble down more juice than previously thought, but it's not time to make Hummer jokes just yet.

First, the goal: Tesla's claims that properly set up home-charging stations can get about a 91-percent efficiency rate.

Rob M. from Teslarati has been diligently tracking electricity used by his home charging station – made up of a NEMA 14-50 outlet that was professionally installed and Tesla's Universal Mobile Connector (UMC) – since June, as we reported here. The results for the month that ended July 21 revealed that the Model S was taking in about 82 percent of the electricity it was pulling from the system, indicating an 18-percent loss of electricity. Most EVs are thought to charge at an 88 to 90-percent efficiency rate.

The downside to his results? About $26 more per month in electricity costs than previously estimated on about 2,400 miles worth of driving. There is a positive upshot, though: his monthly fuel savings totaled about $334 compared to driving an internal combustion engine vehicle.

These early results are intriguing, and make us wonder... Is anyone else checking in on their Model S charging efficiency?


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  • 214 Comments
      Jeff
      • 1 Year Ago
      "Most EVs are thought to charge at an 88 to 90-percent efficiency rate." What a joke of a statement. "are thought to..."??? I love how the passiveness of how this is phrased allows the author to make an inaccurate statement while not taking any responsibility for its veracity. First off, we should know by now that just because Tesla says something, it doesn't make it true. (Remember the $50,000 Model S? Or when they said in their 2006 white paper that the Roadster efficiency including charging losses would be 206 wh/mi, but when the EPA finally tested it, it came to. 300 wh/mi?) Secondly, here's a concrete example of charging efficiency: The EPA sticker for the 2011 Chevy Volt (see link below) showed that it takes 12.9 kwh to charge the battery, and GM has stated publicly that the 2011 Volt uses 10.3 kwh of its battery capacity. (In real-world driving, according to the Volt's on-board energy display, it's typically less than that. But let's be generous and assume the full 10.3 kwh is used.) 10.3 kwh / 12.9 kwh = 79.8%. (Not quite 88%-90%.) http://blog.caranddriver.com/wp-content/uploads/2010/12/2011-Chevrolet-Volt-EPA-sticker.jpg Lastly, I can say that, while high-efficiency charging is an important factor in reducing the overall cost and environmental impact of any EV, it's actually kind of a moot point. Why? Because the EPA efficiency rating for EV's INCLUDE CHARGING LOSSES. So if you want to know the OVERALL cost/efficiency, just look at the window sticker or go to fueleconomy.gov.
        AcidTonic
        • 1 Year Ago
        @Jeff
        http://en.wikipedia.org/wiki/Betteridge's_law_of_headlines "are thought to..." is basically another form of that....
        toumard
        • 1 Year Ago
        @Jeff
        Volt is not a pure EV. It has added weight due to an engine, and lost weight due to a battery pack. You cannot apply those results to all EVs.
      Army Casualty
      • 1 Year Ago
      The savings depends on the car and where you live. I looked at the charts from the original posting, and yes, for me if I had shelled out the dough for a Tesla, would be cheaper in fuel costs, but not by much; we're talking only about $130 a month difference, and frankly, aside from the car cost differences between a Tesla and say a Mazda 3, which is not comparing apples to apples, I see some ignorance elsewhere here about the cost of getting oil out of the ground as opposed to producing electricity. Producing electricity requires getting lots and lots of coal out of the ground or building nuclear reactors or expensive dams. (Wind and solar are prohibitively more expensive and yield little, so if it were possible to produce all of our electricity from that, the cost would be much more than oil.) Electricity would be cheaper if there were not the moratoriums and restrictions on coal that we have. Oil would be cheaper if there were not the moratoriums on drilling and piping we have. The bottom line, either commodity would truly save us alot of money if the Fed would butt out and let the people take care of themselves. And frankly, the difference in cost between fueling gas vs electric would be a slimmer margin and much more reasonable, easing the burden on the hard working common man. Who could then save up some of his money and buy an EV!
        Tweaker
        • 1 Year Ago
        @Army Casualty
        I don't use any coal and why did you ignore NG? An inconvenient truth?
        knowledgehurtsmyhead
        @Army Casualty
        Either commodity would be cheaper in the short run, yes, but continue to pollute the other resources we have left moreso. I'm all for looking back at nuclear, but oil and coal have had their time. How about instead of cutting tax breaks for big oil, using that money towards improving our renewable power resources?
        Mark Bravard
        • 1 Year Ago
        @Army Casualty
        army casualty poison earth a cheaper ride. more just saving on cost of driving saving the earth most white people don,t care.
        Spec
        • 1 Year Ago
        @Army Casualty
        "Wind and solar are prohibitively more expensive and yield little" My 6KW system cost me $13K in parts. It provides more electricity than I need for BOTH my house and my electric car. And it will do so for 25+ years. Prohibitively expensive? I think not. Oh, and that price is before the tax-credit.
      Dave
      • 1 Year Ago
      "Home Tests Show Anywhere Between 82 and 90 Percent Efficiency " "Most EVs are thought to charge at an 88 to 90-percent efficiency rate." The article describes a test showing 82 percent. But none showing 90 percent. Are there any reliable tests showing Teslas that charge at 90 percent? Or is this just wishful thinking?
      Enki Ea
      • 1 Year Ago
      This a nonsense calculation. Please stop spreading lies or "innocent" truths. The EVs will not surpass the efficiency of combustion engines until there is a cheaper way to produce electricity. Right now if people are true to their intentions about comparing one model to another they MUST be grounded to reality which is: electricity production is very very expensive, specially in the US. Everything else is marketing and bs. Imagine if all of sudden all cars running in the streets of America were EVs? What would happen? Would we have enough electricity for every car + homes + industries, etc? Wake up and stop the nonsense. The Tesla is cool but in order to be the REAL DEAL someone should retrieve the old Nicola Tesla papers about energy and production of such from magnetic fields...That is where trouble will brew! Like it once did and all was buried! Remember history my colleagues!
        Grendal
        • 1 Year Ago
        @Enki Ea
        Wake up and start taking your medicine. The internal combustion engine is terribly inefficient and uses only about 20% of the energy from gasoline. The rest of the energy is bled off as heat. An electric motor is substantially more efficient at 85% to 95%. That is why even a very heavy EV like the Model S still gets 89 MPGe.
        purrpullberra
        • 1 Year Ago
        @Enki Ea
        Well, really you are the liar spreading garbage and your diseased 'thinking'. Only idiots say stuff like "imagine overnight..." in order to make a point in the real world. You are a demented puppet to say such lies. It is far easier and less polluting to use electricity even if it's made from burning coal. What source do you have for any of your wild claims? Rush? Some other talking a$$hole who's being paid to fool you? Pure ignorance. You spout pure ignorance. "very very expensive" to produce is so effing stupid that you too simply deserve scorn then ostracism
      • 1 Year Ago
      I love the Tesla. I love Nikola Tesla. I agree whole-heartedly that electric cars are the inevitable future. BUT... The CHEAPEST version of the Model S is $60,000. By comparison, you can buy a new Chevy Silverado pickup for $30,000, and at 18mpg and $3.50/gallon for gas, the $30,000 you saved by not buying a Tesla is enough fuel for 154,286 miles in the pickup. The parts in the truck will probably also last longer and be cheaper to fix/replace. Even if you never spend a dime on charging the Tesla at home and charge it only at the free stations, it will take you 155k miles to BREAK EVEN with a PICKUP TRUCK, on the basis of cost. The upfront investment in an electric vehicle is the single greatest challenge to their rising popularity.
        SeadogMillionaire
        • 1 Year Ago
        You are - conveniently - basing your comparison on today's gas prices, which we KNOW will be another dollar higher in two years. And you are also - conveniently - forgetting that an electric car requires no changing of the engine / transmission / steering / differential oils, no changing of the air filter, probably no changing of the brake pads for 200,000 miles, and only a fraction of ANY parts. So the savings add up quicker. And at the end of 154,286 miles your Tesla (or other electric car) is still running fine, while you are considering either dumping your truck ... and by that time, NO ONE will want a gasoline clunker. OR you are having major internal components of the engine ... or the entire engine replaced, so that you can keep driving at - by then - $8.00 a gallon gasoline !!! NOW ... who made the smarter purchase.
        Koenigsegg
        • 1 Year Ago
        pick up trucks are gay
          Naturenut99
          • 1 Year Ago
          @Koenigsegg
          Maybe that's the meme we need to start :-)
        Grendal
        • 1 Year Ago
        This is an old and pointless argument that is so blatantly ignorant. Why are you buying a new car at all? What is the point of a Corvette, Cadillac, or the Silverado you mentioned? You can always buy a used Hyundai Accent. Then you are really saving money, since the point of driving is saving money. Brain. Use it. Please.
        EVSUPERHERO
        • 1 Year Ago
        Being wasteful with our natural resources has always been cheaper until technology catches up. It has always been cheaper to contaminate our environment, "ie" throwing our sewer and garbage in the streets of the city instead of a sewer system. Until people started dying no one cared. The smell wasn't even enough to stop it. So it is with the ICE.
        JoeP
        • 1 Year Ago
        Yes, but if we run out of oil will you be wishing that you conserved more for the future, or will you still be glad that we used up the last of it to save a few duckets? If you think about our use of oil, running cars on it is the worst option. Think of plastics, fertilizers, industrial processes, etc. If we live in huts barely eking out our existences, will you still be glad we used it all up? They say we only appreciate something when it's gone, but does it have to be that way? I hope not.
        • 1 Year Ago
        Don't forget you don't have to pay for oil changes in a Tesla, ever!
        Avinash Machado
        • 1 Year Ago
        who cross shops a luxury sedan with a truck?
        CaptTesla
        • 1 Year Ago
        And at the end of the day you are stuck driving a Chevy. Abe fun with that.
        btc909
        • 1 Year Ago
        Of course a Tesla will NEVER drop in price. Only a "rich mans toy".
          Grendal
          • 1 Year Ago
          @btc909
          -sarc. :) No one was getting you...
      Kerry Phillips
      • 1 Year Ago
      Saving gasoline is good, saving $$$ is better! Tesla has many other advantages besides lower fuel/energy costs. Access to HOV lanes, preferential parking at some facilities-a long with potential free fueling besides @ supercharger locations, Zero emissions. Can park automobile in your garage/home without any exhaust issues. Reduced maintenance. Zero engine warm up time. Let us not forget, the Tesla is an extremely fine automobile in its own right. My current electricity cost is ~$0.075 KWH or ~ $0.015/mile for a Tesla. My gas saver costs ~$0.10/mile@ $3.25/gallon and 32.5 MPG average. $35k for a Tesla 3, -$7500 tax credit= $28k for a BMW 3 Series equivalent with ~1/6 the fuel costs? Sign me up.
        MFWIC
        • 1 Year Ago
        @Kerry Phillips
        Kerry, I bet the price is $42,000 and with the $7,500 tax credit which is non refundable, will bring it down to $35,000. I thought I was going to get the $7500 credit but it turned out to be a hassle for me to amend, that I just left it alone. The tax credit is non-refundable so that means, if you don't owe any taxes, you can't get any money back. Just a FYI.
      bluepongo1
      • 1 Year Ago
      If you lose sleep over 80% efficiency, you're probably the type that would compare a Chevy Chevette to a Chevy Chevelle ... because they're both Chevys that run on gas * ( In other words Tesla Motors vehicles are not for nickle - and - dimers who put price point over safety and driving.).
      Zaki
      • 1 Year Ago
      I would rather drive a Mercedes E class or Lexus GS and save a cool 20 grand...now that is real savings. Once EVs are actually comparable in out the pocket purchase price, then you can talk to me about savings at the pump. Until then it is just posturing and little more.
        Weapon
        • 1 Year Ago
        @Zaki
        Mercedes E class or Lexus GS is not in the same class as a Tesla Model S though, so it is not really comparable.
        EVSUPERHERO
        • 1 Year Ago
        @Zaki
        Zake, I can only say I am glad early adopters did not share your opinions or we would not have cd players, flat screen tv's, computers, etc... They would never be available to the general public at a reasonable price if everyone were like you, indeed perhaps we would all still be riding horses.
      eric.sales
      • 1 Year Ago
      We have four solar panels each with a max of 130 Watts (e) which we use to recharge at night. I then can travel to the local Super Charger Station which is free. My work also has plug in stations, so we're pretty much covered.
        • 1 Year Ago
        @eric.sales
        yah, well see when there's a few other people with similar electric cars waiting in line to charge...then you will cry wolf with all the $$$ you spent in line
        racergirl79
        • 1 Year Ago
        @eric.sales
        You use your solar panels to recharge at night? HAHAHAHA!!!!! You guys are such religious fanatics you don't even realize your own lies.
        edward.stallings
        • 1 Year Ago
        @eric.sales
        "We have four solar panels each with a max of 130 Watts (e) which we use to recharge at night." They work good at night? So FOS! It takes 85 KWh to recharge a depleted Tesla You would need over 650 of your panels to charge it in one hour on a sunny day at noon. You are so full of soot!
      Steve K
      • 1 Year Ago
      Rich man's toy. You'll never recoup the cost vs a decent 35 mpg sedan and you'll always be limited. A fool and his money are soon parted and Tesla proves this with every car they sell.
        Dave D
        • 1 Year Ago
        @Steve K
        Do you think everyone on the planet should drive a Chevy Geo because they're cheap? Do you also spew your idiocy for anyone who buys a Mercedes or Porsche? Or do you save your special brand of asshatness to share with Tesla owners?
        Steve K
        • 1 Year Ago
        @Steve K
        Those parted from their money also know how to downvote to make themselves feel better about their own irrational choices. Sorry children, down voting won't change reality, but blame the messenger if it helps you sleep at night.
          Stang70Fastback
          • 1 Year Ago
          @Steve K
          Let's follow the progression here: 1. Make comment. 2. Everyone tells you you are wrong. 3. Make new comment stating that everyone else is wrong and you are right. You sound like a 9/11 conspiracy theorist.
        • 1 Year Ago
        @Steve K
        Mmm... probably comparable cost over the life of the car to a $40K sedan, realistically. However, you can't buy a sedan for $40k that performs anywhere close to a Tesla.... and which requires less maintenance and hassle (my Tesla has a "full tank" every morning). So-- the way I looked at it, the Tesla is a "poor man's Porsche Panamera". The fact that it was cheaper was just a bonus as I'm certainly not rich, I'm just not stupid with my money.
        MFWIC
        • 1 Year Ago
        @Steve K
        Steve - the Model S has improved my quality of life. I can't explain it unless you live it. Can you imagine the convenience of never needing to go to the gas station? The Tesla is so quiet on my ears that I feel relaxed on my commute. I look forward to driving it. Especially in traffic it is so easy, you release the accelerator, the car slows down. It is very much like an one pedal driving. Even the AC is quiet. I can hear music without needing to blast it. I have a web browser that saved me so much time when looking for hours of a store and phone numbers. I can hear on demand whatever song by the artist via internet streaming radio just by asking the car. The internet and radio is free. For those that want to go on a trip using the supercharger, they travel for free. I am too lazy to get a free charge, I just do it at home. Unless you drive more than 200 miles everyday, the Tesla is a great car. Almost a year and not one penny on maintenance.
          edward.stallings
          • 1 Year Ago
          @MFWIC
          Not saying that the Tesla is not a great car for some people, but it would be more accurate to say "Unless you drive more than 200 miles anytime and have only one car."
        edward.stallings
        • 1 Year Ago
        @Steve K
        Stop it! The truth hurts!
      • 1 Year Ago
      What is the cost and efficiency when we use a solar powered Super Charging station to power up?
      Richard
      • 1 Year Ago
      In Socal, it will cost you a lot more than $20 to charge the Tesla, unless you had their special late night plan which the rate will be cheap at night but will very costly in daytime which not idea saving if you more than 2 peoples in the house or turining ac a lot of time. To get best rate you has to in a special plan or solar power.
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