Zach Says, let’s keep the conversation simple… so even Elmo can understand it!

Keep it simple





Question: How much electrical energy can we move off the electrical grid and store in an Electric vehicle? For the sake of our conversation, we’ll use the standard electrical outlet normally found in your home as the source of electrical energy.

Before you answer, we will assume you have exactly 10 hours to make the energy transfer, and we’ll also assume you have zero electrical losses in any kind of transformer or rectifier necessary to condition the energy for storage.

Since units of energy can be converted, we’ll use BTUs, and we’ll compare our stored energy to a gallon of diesel fuel, and use a typical value OF 147,000 BTUs a gallon for our calculations.

So here’s the Quiz Question and multiple choice Answers.

Q: How much energy can we transfer from a >standard< 120VAC electrical outlet into a storage  device during a 10 hour window of time? Pick an answer closest to your calculation.

A. An amount equal to 10 gallons of diesel fuel.

B.  An amount equal to 3 gallons of diesel fuel.

C.  An amount equal to one third of a gallon of diesel fuel.

How about posting your answer? you need not use your real name.

Following are some musings about EVs and the road ahead..

How do we consider making  an informed decision as to when we’ll invest?

Among those giddy about pure electric vehicles of the future, I meet few who will make time to run their own pencil.

As I look over the glossy EV ads, I see marketing at it’s best. There she is, a well dressed Babe with her makeup perfect and high heels on.  She’s plugging in her Electric Vehicle into the standard household electrical outlet.

If we study the standard house of today, we note most all the outlets are now wired with 14 gauge wire. If we visit the household breaker box; we see our  120VAC outlets are fed by 15 amp  circuit breakers.  Before we design our EV charger, we best start with the power source. We know that 15 Amp breaker needs to be considered in our design or we could have a huge liability on our hands.   Opening the brochure that comes with a breaker, we see they are typically rated to carry 80% of the current on a continuous basis.

Here’s the math, check me out.. … 120VAC x 15Amps =1800VA, we apply our 20% derate and end up with 1440 VA max that we can safely transfer from the grid to our load (our EV) over this typical circuit.

We’ll be generous here, and assume  zero losses  between the outlet and the input of our energy storage device.  This allows us a maximum of 1440 watts of electrical power. Since a watt is a power figure, we can convert it to BTUs, Calories, or other common units of energy we are familiar with.  A constant 1440 watts provides us with 4913 BTUs an hour.  If we multiply by 10, We transfer 49,130 BTUs of energy into our EV in a 10 hour period, which might be a realistic overnight charge period of time.

If we compare this energy to kerosene or diesel, we see that we are able to transfer the equivalent of one third of a gallon of energy over our standard plug in over a period of 10 hours. This might give you some idea as to how much energy is in these fuels, and why the Russians use Kerosene in their booster rockets when they put  payloads into orbit. Energy density has a lot to do with how much you can take with you, and how much work can be done.

Now that we know what amount of energy we can transfer into our EV, we shouldn’t expect to use it all, we don’t get everything back we put in.. We have losses of several kinds between the energy storage unit and the rear wheels and we need consider that on many days we might use far more energy than our transfer rate allowed just to keep the inside of our car warm or cool, and the windows defogged enough to safely see out. Consider that day in heavy traffic, stop and go traffic demands a lot from a battery, but keeping the car warm or cool can take far more energy than our home electrical outlet can deliver.

Certainly, there is hope! All you need do is call in the electrician and buy the more advanced charger and enjoy a fuller state of charge over the 10 hour window. In some cases, there’s little need to call in the gang, as the breaker box might be close, and you could have your new charging station installed for less than $3000.00 dollars.

Recently, we saw Prince Charles’ Aston Martin DB6 put to work as part of the Royal Wedding Ceremony hauling William and Kate.  Some of the AE enthusiasts praised Prince Charles for having converted the car to run on clean ethanol made from excess wine. We skeptics might ask just how much excess wine there is in UK, and how might the effort ‘scale up’? Maybe we simply command more wine to be made?

Our homes have been designed to carry the electrical loads we normally carry, and of course our electrical grid is designed to carry what’s typical, we barely squeak by on peak load days in many areas.

When it comes to the Grid and rebuilding it to meet the new increased EV demand, those who are most optimistic will tell you the grid isn’t used much at night when the charging will be done. They have no concept of how energy is made or stored. In reality, the grid is far more dynamic than many understand.. there are energy reserves that are charged during  off peak hours, and these same reserves are used to cover peak loads.  The difference in cost between a peak KWH and an off KWH can be huge. In the wholesale market, a KWH might trade for five cents or well over a dollar during the hours or minutes of high peak loads brought on by a number of circumstances. An example of some of these energy reservoirs can be studied at hydro facilities and Power South’s ‘CAES’ compressed air energy storage system is a great example, and more of these solutions are under study to meet future demands.

This huge variability in price per KWH is seldom seen by the consumer, but if we decide to remove a good portion of our off peak production hours, we should expect the price per KWH to go up dramatically, fact is, what proponents of EVs call cheap electrical energy today might become far more expensive. If we were to convert half the cars on the road to EVs, we create a mind boggling need to increase capacity in electrical power generation and capacity to haul that energy to the point of use. How does that get paid for? Remember… A subsidy is paid out of your back pocket.

What did I get wrong?








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20 Responses to Take-the-Quiz-Energy-Storage

  1. Mike says:

    You pretty much forgot all about any charging losses.. Chuckle !!! Score one for the full EV group !! You really go beyond fairness George.
    Everything else is DEAD ON….
    Electricity is the last good deal and it’s about to catch up with the others. The only place a full electric could really shine is a home CHP unit and even then the numbers are the only thing that tells the truth. Then again that would trigger a knee jerk tax remedy. The main problem with that is red fuel dye for electrons. Then comes the on board GPS for tax purpose that has already had laws passed to bring it about. When I look at EV’s I think,”WOW, I could pump that thing full of electrons for some of the most unlikely sources!” But Gubbermint has already taken that into consideration and has pre-rigged the game. They’ll only be a great deal for the early owners but then again they are expensive 🙁 … I hope to get some of the guts of a good used one some day for use on small tractor or maybe a line Diesel Hybrid I’ve been dreaming about ( since nobody sends one to the USA and we’re obviously NOT going to build one ). Shouldn’t be hard to do since the day the battery pack dies marks the end of the EV life when the optimistic owner prices a battery pack… All that aside and your obvious generosity ( not factoring in all of the losses ) to the EV group, Id say they’re a great deal if you only live a few miles from town.

  2. George B. says:

    For those who are looking to build their own EV, why not start out with an elegant solution at a fraction of the cost? I have a Ford Think for sale, It’s in very good shape. It needs new batteries, but considering it’s a very good excercise in light weight composites and alloys, you could buy a street legal car and add your more advanced motor and batteries! $2600 get you a four passenger Ford Think Neighbor..

  3. Mike says:

    I know there are inefficiencies with diesel conversion too George but I’d say the net losses of both the real gains are only going to be for a short period.

  4. George B. says:

    We purposely avoid the discussion of losses here.. we all know you can’t go too far on one third of a gallon of diesel and take your lunch with you. Some might bring a record breaking car into the conversation that cost $450,000 or more to build and was piloted by a 125 pound man, but I think we need stay focused on reality and realistic transportation..

  5. George B. says:

    “Electricity is the last good deal and it’s about to catch up with the others.”

    Mike ..I do agree with your statement..there are those who learn the hard way when they attempt to compete with the power company. They have ‘economies of scale’ that make it very difficult to beat their production costs even when your fuel is free!

    The intent of this article is to convey just how much energy there is in the typical hydrocarbons we use…. gasoline, or Diesel.. and the amount of energy we can store in a very lightweight compact package. I can easily add the equivalent of a days worth (24 hours) of electrical power out of the standard plug in… into a corner of my day pack!

  6. T. Lindsay says:

    Are you getting 147000 BTUs from your gallon of diesel? If we take that diesels have a thermal efficiency of 50% with some variance either way, plus losses in generation, wouldn’t that mean you should pack 2/3 of a gallon or more in your daypack to have the same energy available to you?

    • George B. says:

      Hi T,
      My goal here is to discuss sources of energy and their storage size and weight. We can do this totally outside the discussion of how we will use the energy. I think it’s a lot like the discussion of money, we can discuss whether you have it or not without discussing how we’ll use it. Let’s pretend we will use this energy source (a fuel oil) for our ‘reformer’, then convert it to hydrogen for our on board fuel cell. Regardless of what we do, we expect losses not gains. When we discuss hydrocarbons like gasoline of fuel oil, we know we need add a lightweight plastic tank to carry it. If we are going to use electrical energy off the grid, we need to include the storage device as part of the mass as well, and that mass burdens our efforts, but isn’t that another discussion? It’s a fact that people get lost in the details, and same as magic, some assume gains where only losses live.

  7. Quinn says:

    Warning: OT Content

    George, we had this discussion a while ago, but I noticed the plug protectors in the 110V receptacle on the wall behind Zach. I wonder how he’s going to learn about electricity with those things keeping him from sticking paperclips, hairpins, the car keys, etc. in there.

    • George B. says:


      When it comes to the electrical grid and our present ability to transfer energy from the grid to a large number of EVs, Zach already knows at least as much as Tom Hanks and Danny Devito who played parts in the totally misleading documentary “Who killed the electric car”.

  8. Richard says:

    If they have their way and get people to buy 100,000 dollar electric car and many do. Then where does road tax come from. Right now it comes from gas and diesel. If people use electricity then when do they pay their road taxes.
    P.S. Yes a lot of electricity will be used if you have to heat an electric car in the north.
    What are they thinking. Too many kilowatts to heat a car with electricity. Right now we heat our cars with waste heat.

    • George B. says:

      Richard, you make a good point.
      Imagine…. That cold Fargo morning, You’ve kept your EV in the heated garage overnight because the day prior you used all the energy in the battery to defog the windows and de-ice the dash!
      In order to keep from freezing on the short hop to work, you’ve warmed 175 pounds of bricks in the pre-heated oven and placed them in the foot wells. Those Dumb Ass EV haters never even thought of this!
      The bulk of people who are supportive of Electric Vehicles do not have any interest in basic physics, energy conversion, losses, cost per mile. They are driven to support the EV through their religious zeal; remember the opposite of skeptical is gullible. I read one post by a brain dead green energy guy who said you make energy forever off solar and other green machines, so cost doesn’t matter. I suggest we offer to pay him a half percent interest on his savings forever.. but he would only tell you “that’s different”.

      Your mention of road taxes is just the tip of the ice berg. There are quite a few States that are already looking at new methods to tax vehicles because of the high efficiency gasoline and diesel vehicles on the roads now. Fact is, they can see the road tax revenue figures monthly and have a pretty good idea of the trend, and some are headed down. Some State Legislators have already stated, there will be a need to levy a special tax on EVs.
      A rabid environmentalist is easy prey, as he doesn’t need to be convinced of a thing! I expect to see the term ‘Free Range’ and possibly ‘Organic’ across the back of EVs soon. That would be enough for some to make the purchase
      alone….If only they can find a way to put the entire purchase on credit with no down payment, no interest….. I’m sure people in our government are working on a plan now.. to provide financing, just like they provided for housing ?

      EVs look attractive because those who are attempting to promote them suggest you’ll be running them for near free! In reality they are looking at a fraction of the cost, and even people in our Government help with the deception by providing subsidies. Reality starts to set in when three people on the same peg pole transformer attempt to charge their EVs so they can reach work in the morning. The fact that the transformer becomes hot to the touch, and attempts to heat all outdoors is no immediate concern to the EV owner, those losses are the Power Company’s losses right? It doesn’t take a genius to know that the grid will need to be rebuilt if EVs catch on. The difference between the EV nut and the rest of us is; we can anticipate the staggering cost of upgrading the power grid, the huge surcharges created by the transfer of our wealth to Green Energy Scammers, and that all important window of time when peak loads overwhelm the grid. An environmentalist will tell you it can all be managed, night time is off peak hours, blah blah blah. We will pay far higher electrical rates very soon, the Green Scammers are Parasites and they will prove to add no value long term, they have bought elected officials, and between them and nuts who >voted< to volunteer to pay more for electricity even though they had green hydro in the first place will assure an even larger chunk of your money goes to energy for years to come.

  9. Lynn says:

    Hey George,

    One thing about Kerosene, and why the Russians use it: It’s easier to handle than liquid Hydrogen.

    LH2 has much better energy density, but it has to be kept at minus 423 degrees. It’s done because you get a lot more boost out of the booster, but at a tremendous cost of keeping it cold right up to launch.

    Kerosene (RP-1) doesn’t need special handling, it’s easier. That’s why it was used in the Saturn 5 first stage.

    — Lynn

    • George B. says:

      good comment lynn

      When I compare energy densities I always think room temp, Kerosene is tough to beat there..I can’t imagine the added costs of liquid hydrogen… but I’m sure there’s some nut who wants to put it in his car and use a solar panel to make it …

      There’s a connection between NASA’s use of Liquid Hydrogen and that of gasoline in a car. Both NASA and the Average driver are making a trip where energy densitiy is important. In the case of NASA, the cost of producing the fuel and storing it are not priorities. In the case of the automobile, we should be far more interested in real cost per mile. This is where EV enthusiasts go out of their way to decieve themselves. If you were forced to buy their car and their fuel, they’d call it free energy. I Guess Dictators have been using ‘free energy’ for longer than 1000 years now.. nothing new..

  10. Russell Furzer says:

    I did spot one thing you got wrong – That DB6 aint no AUSTIN martin. Its an ASTON-MARTIN.

    The rest is right on

  11. Russell says:

    Hey George!

    Still wrong. Not “Auston”. ASTON!

    We Aussies wouldnt spill our beer over that ‘tho – even us Brit sportscar addicts (I am nearly cured- might just have a relapse after the mention of the Lotus 7)


    • George B. says:

      Russ… I wonder, is there a limit to how many edits a person can make? This reminds me. People who write books on behalf of others say that 80% of the work is left after the book is written. It seems the mind can be pre-occupied with the story, and miss a lot of basic stuff. This incident brings to the fore front the question.. “How many proof readers would I need to hire just to correct the errors at Utterpower? Please do keep it up, I need all the help I can get 🙂

  12. Russell says:

    Hi George

    I do get it. The meat is much more important than the ketchup. I’d much prefer to see a new idea for the day than an insignificant edit!

    This series of comments reflects more on my pernickety nature (at least about the giants of Brit engineering) than any negative reflection on your super website

    • George B. says:

      Thanks Russ, we both know there’s a love hate relationship with British cars, things to love, and to hate at the same time. And the British Bikes, the 1960s BSAs were soooo beautiful! But I’d like to find the guy who decided to use a Zener diode for a voltage regulator in some of the bikes.

  13. Russell Furzer says:

    I think that the reason that I found myself deflected from the real issue was the units used in the quiz.

    Although the interest in brit cars (and flying US made aeroplanes) has helped with a good degree of comfort with some non-si units (eg inches, miles, feet etc), I really blank out a bit with the (to me) weird ones like BTU’s.

    My brain has been programmed by our school system to think of heat and other energy in Joules and power in Watts.

    As I follow your math (we say maths) I step off solid ground after working out that the power point can deliver 1440 watts. The energy unit that I like is joules and so I need to embrace the BTU.

    Working out that conversion from the ground up is not KISS!

    What I uncovered is the oddity that all the elements of the BTU per US Gal are defined in (good-ol) SI units.

    The pound is actually defined as 0.4355(etc) Kg
    A deg F is 5 ninths of a deg C

    A US gallon is the old Queen Anne wine gallon (as opposed to an ale gallon) that the Mayflower settlers used (the Brit Imperial Gallon equal to 10 pounds of water is newer fangled).

    That wine gallon was supposed to be 8 troy pounds of wine (those weirdo troy pounds are only 12 ounces not the regular 16 AND those are troy ounces which are 480 grains. A grain of course is DEFINED as 0.065 (etc) grams). That was too hard for London wine merchants so the wine gallon was changed to 231 cubic inches back when an inch was defined as the width of 3 kernels of barley.

    Happily an inch is now defined a 25.4mm (I can feel the bottom with my toes again) and so a US gal is 3.79(etc) Litres

    It all works out that your 147000 btu/usgal diesel is about 41MJ per Litre which is quite a bit better than ours which is about 37.

    Is US diesel better stuff? or have I stuffed my math(s).

    In any case the 1.26 litres of your hot diesel that is the equivalent of the output of the power point would get my pretty efficient TDI about 23Km, which doesn’t get me from home to the petrol station and back again! And its a mighty long way to the nearest EV charging station.


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