Watt Hours; Calculating E-bike Range

August 1, 2012

Watt hours is a way to measure the energy capacity of a battery pack, so you know what to expect from your new E-bike in terms of range performance. To calculate the watt hours (WH) of a battery pack, simply multiply the voltage by the amp hours (Ah) of the pack. A 36-volt 10-Ah battery pack has 360 watt hours (36 X 10 = 360). If you are nitty with your energy usage, each mile you travel will cost you about 20 watt hours. Therefore a 360 watt hour pack will get you about 18 miles. The range can vary widely depending on where and how you ride.

Watt hours determine the range of your bike, the cost of your bike, and the weight of your bike….three very important factors to consider when buying  an electric bike.

Batteries come in different cell qualities. Name brand cells such as Samsung, Panasonic and A123 will last longer (number of charge cycles)  than no-name Chinese cells. Of course if your pack consists of name brand cells, the cost per watt hour will be much higher.

You want to throw that salesman for a loop? Ask him what brand and what chemistry is in the cells that the battery pack uses. If he can’t answer that, speak to someone else…or do your own research online.

A 250 watt motor will burn 250 watt hours in an hour and will last you an hour and 20 minutes at full throttle on those 360 watt hours, but it will not provide you with very much assist.

A 500 watt motor will burn through the same pack at full throttle in less than 45 minutes, but you will be given twice as much assist as you get from the 250 watt motor. If you are nitty with your 500 watt motor and run it at half throttle (250 watts) and pedal a lot, you will get the same efficiency as you get with a 250 watt motor. However the exhilaration of  available electric power is sometimes hard to resist.

Just for practice, lets count the watt hours of some of the bikes  that have been reviewed on The larger the watt hours the longer the range, the more expensive the bike, and also the heavier the bike.  So we will also list the weight of the E-bike, the price of the E-bike, and the quality of the cells.

We will list the range that the E-bike company claims, and then use our “20 watt hours per mile” standard to come up with an EB estimated real life range. In our experience most riders will be less efficient  than 20 watts per mile (its hard to lay low on the throttle), so this is a generous figure. If you are getting better than 20 watts per mile (the lower number the better) you are a real electric juice miser, or an athletic pedaler, and are probably moving at just a little fast than regular bicycle speeds.

Faraday Porteur

  • Faraday Porteur (read story)
  • $3500 (Kickstarter price)
  • 110 watt hours (really puny)
  • Claimed range: 10-15 miles
  • EB “Real Life” range: 5.5 miles
  • Weight: 39 Pounds
  • Motor: 250 watt front hub motor
  • Battery cells: A123 18650 cells LiFePO4
  • Battery life expectancy: 1000 charges
  • 2 year warranty on battery (damn good)
  • Replacement pack price $700

As you will see, compared to the other bikes on this list, this bike has a puny battery pack, especially considering its relatively high cost. It does have light weight however. This is the lightest, most stealthy looking bike on this list.  However as you will see, a mid-drive bike like the Focus Jarifa, has 4X the battery at about the same price, and its only 6 pounds heavier.


Currie Ezip Trailz

  • Currie Ezip Trailz (read review)
  • $500 (shipped!!!)
  • 24V X 10-Ah =  240 watt hours
  • Claimed range: 15-22 miles
  • EB “Real Life” range: 10 miles
  • Weight: 69 pounds
  • Motor: 450 watt brushless Currie  Drive system
  • Battery cells: sealed lead acid (SLA)
  • Battery life expectancy: 100 charges
  • Battery warranty 3 months
  • Replacement/ extra  pack price $140

This bike is as cheap as you will ever find any decent E-bike. The key to this bikes low cost is that it uses lead acid chemistry and its very heavy, especially given its low watt hour rating. (the quality of lead acid cells is very dubious, and the battery will not have much of a life span if it is not meticulously cared for). Lead acid is an older technology. Be warned you will not get 240 watt hour range out of this E-bike for very long. Only when the battery pack is brand new will you get the  EB range of 10 miles.


Specialized Turbo

  • Specialized Turbo (read story)
  • $7,000
  • 36V X 9-Ah =  350 watt hours
  • Claimed range: 25 miles
  • EB “Real Life” range: 18 miles
  • Weight: 42  pounds
  • Motor: 250 watt geared hub motor
  • Battery cells: lithium polymer
  • Battery life expectancy: 600 charges
  • Battery warranty 2 years
  • Replacement / extra  pack price (unknown), has a swappable battery

This bike has a ridiculously high price ($7000) when you consider the small size of the lithium battery (350-WH). The bike is slightly more efficient than most hub motor bikes because it uses thin road bike tires.


Currie Izip Metro

  • Currie Izip Metro (review coming soon)
  • $2600
  • 36V X 10-Ah = 360 watt hours
  • Claimed range: 20-35 miles
  • EB “Real Life” range: 18 miles
  • Weight: 55 Pounds
  • Motor: 500 watt geared hub motor
  • Battery cells: Samsung 18650 cells (high quality)
  • Battery life expectancy: 500 charges
  • Battery warranty 1 year
  • Replacement Battery $600 (plus labor charge, battery is built into bike)

The Izip Metro has the rare property of having its 360 watt hours of battery built into its purpose built frame.  Many other bikes on this list happen to have this feature, the Faraday, the Stromer, the Optibike and also the Stealth Bomber. However, this is the most affordable out of those E-bikes.


Stromer Electric Bike

  • Stromer Electric Bike (read review here)
  • $3000
  • 36V X 10-Ah = 360 watt hours
  • Claimed range: 20-45  miles
  • EB “Real Life” range: 18 miles
  • Weight: 62Pounds
  • Motor: 600 watt direct drive hub motor
  • Battery cells: Samsung 18650 cells (high quality)
  • Battery life expectancy: 500 charges
  • Battery warranty: 18 months
  • replacement/extra battery  $700  (removable swapable pack)


Focus Jarifa Mid-Drive Bike


  • Focus Jarifa  (read review here)
  • $3500
  • 26V X 18-Ah   =  468 watt hours
  • Claimed range: 80 miles
  • EB “Real Life” range: 31 miles
  • Weight: 45 pounds
  • Motor: 300 watt mid drive
  • Battery cells: Panasonic 18650 cells (best quality)
  • Battery life expectancy: 500 charges
  • Battery warranty: 2 years
  • Replacement / extra battery $800 (removable, swappable pack)

300 watt mid-drive motor…this is the most efficient bike on this list, meaning it will get you further per watt hour (we estimate 15 watt hours per mile).  This bike uses Panasonic 18650 Lithium Manganese cells (LiMn) which are considered the highest quality Lithium cells in the industry.


Pedego Interceptor


  • Pedego Interceptor (read review here)
  • $2300
  • 48V X 10-Ah = 480 watt hours
  • Claimed range: 15-30 miles
  • EB “Real Life” range: 24-miles
  • Weight: 60Pounds
  • Motor: 500 watt direct drive hub motor
  • Battery cells: lithium manganese soft cells (LiMn)
  • Battery life expectancy: 500 charges
  • Battery warranty: 1 year
  • Replacement/extra battery $600 (removable, swappable pack)


  • Currie Izip Express 720 watt hour
  • Currie Izip Express (review coming soon)
  • $5000
  • 36V X 20-Ah = 720 watt hours
  • Claimed range: 45  miles
  • EB “Real Life” range: 36  miles
  • Weight: 62Pounds
  • Motor: 750 watt  mid drive
  • Battery cells: Samsung 18650 cells (high quality)
  • Battery life expectancy: 500 charges
  • Battery warranty 2 years
  • Replacement Battery $1200 (plus labor charge, battery is built into bike)




Optibike 850R

  • Optibike 850R (read review here)
  • $12,000
  • 36V X 26-Ah   =  926 watt hours
  • Claimed range: 40-80 miles
  • EB “Real Life” range: 46 miles
  • Weight: 60 pounds
  • Motor: 850 watt mid drive
  • Battery cells: Generic 18650 cells (average quality)
  • Battery life expectancy: 500  charges
  • Battery warranty (limited): 3 years
  • Battery replacement cost $2000 (plus labor charge, battery is built into bike)

The Optibike contains an amazing amount of battery given its small form factor and weight. However, its high cost is a definite downside. The replacement cost of the Optibike battery pack is a whopping $2000, and bike must be hazmat-shipped (expensive) to Boulder Colorado to replace the pack, since the battery is built into the frame. Also this makes it extremely inconvenient for warranty support. See how one user repaired his bad Optibike battery pack himself in our story here.



  • Stealth Bomber  (read review here)
  • $12,000
  • 83V X 20-Ah = 1500 watt hours
  • Claimed range: 50  miles
  • EB “Real Life” range: 50+ miles
  • Weight: 125 pounds
  • Motor: 4500 watt direct drive hub motor
  • Battery cells: LiFePO4 soft pouches
  • Battery life expectancy: 1000  charges
  • Battery warranty (unconditional): 1 year
  • Battery replacement cost $2000 (plus labor charge, battery is built into bike)

The Stealth Bomber is capable of 50-MPH, but even with its gigantic 1500 watt hour battery pack you will drain the pack very quickly with its 4500 watt motor. With the Bomber you pay for all those watt hours not only in high price, but also in weight (125 pounds). These days it’s simply impossible to have all 3…a cheap, lightweight bike, that holds a lot of watt hours.


Eric has been involved in the electric bike industry since 2002 when he started a 6000 square foot brick and mortar Electric Bike store in downtown San Francisco. He is a true believer that small electric vehicles can change the way we operate and the way we think.

  • gdays

    Thank you for taking the time to do this article. currently im trying to build a mid drive bicycle, so this with be very helpfull on choosing the right configuration.

  • ian

    having all 3 is possible, home builds with a 9c and hk lipo will do it.

    • M_111

      What have you found your top mph is with the 9C? We got up to 55mph on a standard old mountainbuike using several 45C LiFe batteries (the true Ah is 1/3 the lead acid equiv since it is for starter battery use, but we had access to a surplus. I believe we started with 24Ah 45C and it was flexing the chassis. The pack lasts longer than the base motive pack on the Zero MX due to the weight and power delivery on the Zero. But only about 10mpH difference in topspeed. We were looking into lower C rate, but higher aH and V for delivery, and as I am sure we all are, trying to save money! I saw an affordable 128Wh pack, but the c rate is only 2.

      • Jeff Kephart

        Do the math, C=Number of times the Ah that a pack can
        discharge w/o damage. So a 20Ah “5c” pack can do 100A
        (for a very brief time)
        If you need 1000watts out of a 24v/24ah you need 50c
        just to avoid damage to the battery.

        • chad

          WRONG, c rating is not the # of times. C rating is the rate at which you can safely discharge a battery. For a 2000 mAh battery with a 15C rating, the continuous current that may be drawn out of the battery is 2000 mAh x 15 = 30000 mA, or 30 Amps (A) (divide by 1000). Lets take your example of 1000 watts needed at 24v. 1000/24v=41.6 amps needed. volts x amps = watts. So if you have a 24v batter with 24ah capacity and need 1000 watt discharge rate safely you would need a 2c battery. 24000 mah x 2 = 48000 ma or 48 amps. 48 Amps X 24 volts = 1152 watts, volts x amps = watts. BTW c rating is constant discharge and not “brief time”, battery should also list peak or burst rate.

  • cccccttttt

    Appreciate the article. Watt hours per kilometer is a simple
    international measure of efficiency that works for bikes, trikes, and
    cars, When will the US public shift to metric like the science, military,
    and international community?


    • ElectricBIke

      Yeah the metric system makes so much more sense.

      America is so backwards sometimes.

  • cccccttttt

    To prepare junior high students for ebikes and ecars,

    made up a very brief “Electric Fractions” blurb at

  • Mike

    I would love for someone to give a review of the water bottle type batteries (downtube mount) now coming out of China. I’ve even seen one rated for 36 volts at 12 amps–lithium ion. The nice clean stealth look is attractive. An added bonus is you could just carry an extra battery and swap it out in seconds. Any experience out there? I’m hoping they are not junk.

    • Alex Goldsmith

      It’s useless to swap out the battery. You might as well just connect them in parallel and not make more effort by stopping to swap them

      • leo

        i prefer to swap batteries as i know what range i have then 🙂

  • juliansmm

    Really good article. I don’t understand what happens when I have a 500W and my battery is 36V x 10aH. I am going to have less speed or less range or both???

    • ElectricBIke

      500 watts is what the motor is rated for and tells you how much wattage it can handle. 36v x 10ah means you have a 360 watt hour capacity battery. If your motor were to burn 500 watts it would go through a 360 watt hour battery in about 40 minutes at wide open throttle….theoretically.

      • Jeff Kephart

        In general V=Speed A=torque.
        Check your CONTROLLER for amp rate that it can handle.
        Volts Times Amps=watts ie 24v into a 35amp PWM is 840w.
        A currie ‘450w’ motor can handle this, the SLA controller can do this too
        (if you feed it the right battery, no way on a factory pack!)
        Amps feel great, but can severely impact range.
        I ran an ammeter in series with the battery and could watch the load
        and feather it out to max the range. 15mph vs 19 was around a 33%
        savings / range increase!

  • Mike Dixon

    Hi great artical. Can you help me please ? Im looking at building a stealth looking bike similar in design to the volton. At minimum i would like to use a 52 volt 2000 watt geared blacklightning motor from HPC with a Li NMC 10 or 12 amp/hr pack in the tube 70mm by 90mm 480mm from the head stem to the crank. can you please tell me if its possible to fit this amount of battery in this space ? If not how could i find out this info ! The idea is to build a bike that can do 60 kph min as discreetly as possible. Basically the more batteries i can fit in the frame bigger the motor i can use so how to find this info love to know.

    cheers Mike

    • Jeff Kephart

      There is not much DISCREET in a bicycle traveling at 60kph. The cops will be all over you.

  • B-Rad

    Hi Good article, but I am running into confusion when I am on endless sphere trying to understand the battery jargon used.
    A lot of riders use 4s2p to describe the voltage and capacity of their battery pack.
    I understand that this must mean 4 cells or batteries in series and then those 4 cells or batteries connected in parallel.
    So if I had 3 volt cells at 5 amp hours each the above pack would then be 12 Volts rated at 10 amp-hours.
    Series connections raise the voltage and parallel connections raise the amperage.
    My confusion is when they say 4s2p how can i possibly understand what the voltage is they are running?
    Is there a standard for this?

    • ElectricBIke

      Lipo packs charge to a safe maxium of 4.2 volts per cell….so to be real save and easy lets say 4 volts. A 4s is 4 cells….so figure around 16 volts. If you wire three of these together in series you have a 48 volt pack (what most endless sphere guys would do). If you wire together in parallel you would have tripple the capacity (in amp hours) and the same voltage.

      Hope that helps.

    • Jeff Kephart

      The jargon comes from the RC car industry. S is series (add voltages up)
      P is parallel (add the current/ah capacity)
      My 36ah pack was 96cells (286650 cells) 12P8S to get 24v (29.6 charged)
      It’s a $500 from china battery, but was a BEAST (45mi range with my fat ass
      doing nothing, in hills of Pittsburgh.) 70mi in Florida!

  • jsnyder

    What do you suppose they mean by saying 9ah but with rating of 15ah – that’s confusing. Should I think the range is based on the 9 or the 15? Any idea?


    • micro

      It’s 15 amps, not 15 amp-hours. It’s a detail that’s safe to ignore. The capacity is 9Ah.

      • Jeff Kephart

        I disagree the AMP draw can have dramatic effect on battery life, esp
        with SLA. Hitting a 10ah vs a pair (20ah total) with 800w load I went
        from 5.8 to 19miles. Same trips etc. Same for keeping out of the throttle,
        2/3 throttle drops 4mph and around 1/3 the amp draw.

  • Sunil Kumar

    whats gear diameter in dc motor

  • john

    Maybe put a hub motor and battery on a pit bike. Or put it on something like a Taco 22 or Road Rocket frame. That’d be sick.

  • mtseok

    Ebike does not use total wattage like 360w (36v x 10ah) out of battery capacity. Controller or BMS cuts off the power supply when the battery voltage drops to 30v or something. Do you consider this in your calculating mile per watt? We just use the difference of full charge capacity and the safe cut-off setting, isn’t it?
    – confused from Korea –

    • Jeff Kephart

      Indeed and the overall size of the capacity divided by the PWM current can
      have a large effect on range. On same bike I went from one 10ah@24 SLA pack
      to twin (bike then weighed 94lbs!) And went from 5.8mi to 19mi range.
      Closer to 3x than the 2x that you would expect!

  • Gemini by NexxtDrive

    Appreciate the attempt at getting “real world” range estimates from the advertised ranges. However i would like to understand how the “20 watt hours per mile” standard is arrived at. What sort of drive cycle does this imply? On the flat? If not what is the assumption?

    • K_2K

      Seeing no reply in 8 months, I’ll shoot.
      I’ve seen this as roughly a 15 MPH no assist figure for 180 lb rider, or 20 MPH for 150 lb rider. Always on the flat.

      The idea is that a non-enthusiast travelling modestly can get to the store, work, what-have-you without working up a sweat, and needs about 20 watt-hours to go each mile if they don’t intend to pedal.

      Naturally, without a windshield, even a small increase to 25 or 30 MPH would add a lot of drag and reduce the number greatly. how much drag? bending over? sitting upright? Hills kill your distance, stops and starts are show stoppers. Trying to give figures for 4% grade vs. 2% grade would be difficult. My car gets about 10% less miles per gallon from here to work than from here to the store, which is about the same distance with one large hill added to the work trip. The bike distance shows the hill even more drastically because I hardly use the motor at all on the flats, and the drag coefficient is probably off the chart compared to the car.
      I guess I’m just trying to say it’s very difficult to put all those variables in one spreadsheet. I know need something rated for 9-10 miles to get 3 miles to work and 3 miles back plus the hills and stops/starts. That’s about 200 WH at end of life. A 250WH battery (80% after a few years=200) should do the trick. I won’t hesitate to get a little more, but if a certain setup can’t give me that much, I can’t consider it.

  • ab

    How to decide battery for e-bike with 3.5KW motor running at 48 V

    • Jeff Kephart

      As big as you can afford!

  • 3 years later no one has done any better for giving real world wh/m estimates.

    estimates without average speed figures are useless. on top fo that, what kind of riding?
    stop and go? hills?

    i very much applaud the necessity to start tracking this stat wh/m in detail and making meaningful figures out of it. these estimates are gold. and yet they are a million miles away from being useful as they don’t give meaningful speeds/ride inclination/stop and go acceleration patterns, rider weight, wind, etc….

    • Jeff Kephart

      My quotes are WOT (wide open) and I explain the terrain.
      Run one of these things non stop around a velodrome and you’d get
      a whole other (pie in the sky) set of numbers.
      I also have found that 3/4 or so throttle can reduce draw 33%
      so 19mph vs 15 is 15 vs 9 amps.
      Having an ammeter you can see and adjusting your habits accordingly, HELPS!

    • Jeff Kephart

      You supply $10,000 worth of lab grade gear to 10 of us and we’ll give you your data.
      WAKE UP PEOPLE! How often does the car match the EPA sticker mileage?

  • Jeff Kephart

    Might also mention that any SLA pack and most lipo etc the “ah” rate is across 20hr
    discharge. The “10ah” currie packs at the 35AMP discharge rate are more like 4-6ah!
    (I got 6mi in Pittsburgh hills on one battery but 19 when I doubled the pack in parallel)
    So, discharge RATE (amperage / wattage of the controller) affects SLA in a very bad
    way and LiFeP04 or LMN less so. A 36ah 24v LiFeP04 on same ezip went 45mi and
    was not quite dead!

    • jacob

      any one can help me.i have 900 watts motor of my skateboard what is the best battery i can use?.is it enough 36v 20ah lithium battey?.

      • Jeff Kephart

        Is your ORGAN DONOR CARD current?

        A 450w motor and 35A 24v controller will drive a 95kg person on a 45kg bike at around 30kph!
        I think you either are a TROLL or have mental issues.

        • leo


  • Jeff Kephart

    Correction, the motor on the ezip was BRUSHED not brushless. Also the brushes are
    unobtainium. (good thing they are good for 5,000+miles!)

  • Derek Johnstone Macrae

    LiNiCoMnO2, i have a 48 volt pack, giving 960 watt hours, the motor is a 1000 watt hub, im getting around 35 miles at 25mph, on level tracks such as canal paths at 15mph, i get close to 50 miles, the pack weighs a measly 6 kilos and cost just £240, if you self build, even cheaper, the chemistry has been out for 2 years and has been further enhanced by NMC cells, which are even more robust although more expensive, expect them to last at least 1000 charges at 100% and around 3000-5000 charges at 70%, that around 6 years of daily use, ali express and ebay now stock mnc and LiNiCoMnO2 batteries, and you can easily pick up 20 amp hour packs for around £250 direct, or £350 uk stock, thats around HALF the price of lipo4 20 amp hour packs

  • Annemieke

    Does the explanation about how to calculate the range performance of an e-bike also apply to an e-bike with pedal assistance? Or is it only applicable for e-bikes of which only the motor is used?

    • Jeff Kephart

      The only way that makes sense is to speak of motor only.
      Since, if you pedal, range could be unlimited!
      My tests are real street riding, and I explain terrain. Since rare is the use
      that is ONLY flat and NO wind etc.

      • Annemieke

        What I mean is if the calculation is for the use of a motor only without peddaling at the same time? Or is the calculation for the motor usage together with peddaling, so that the motor is meant as assistence to a speed of e.g.18- 23 km/h?

        • K_2K

          Right, motor only. No pedaling.
          When you help, you are providing your own human-powered work not from the battery. So the distance is what the battery provides plus what you provided. You have to calculate each separately and add them. This is why the different manufacturers have different ranges for essentially the same bike. They each assume a different amount of help from the rider.

          Some of those might be reasonable assumptions. If the highest gear of one bike puts standard pedaling speed at about the top speed of the motor and another bike has a higher gear, the rider of the latter bike is more likely to go it alone for a little more speed on flat ground, and get more miles on his/her own power. In my case, I often used the motor for take-off and hill climbing. On flat ground, I’d feel no help past about 18 MPH, so I turn it off and pedal myself up to 25 or 30. The longer I don’t have to stop, the longer my total range with this assisted riding. You just can’t compare specs this way, except that a better bike with better gearing and lower resistance parts/wheels, etc. would help the same as a better non-electric would help any rider.
          Still, I want to know I can get to work on hotter days without helping at all, and for that I use the author’s calculation from Watt-hours.

  • Jon

    How many miles at full throttle will a 500 watt 36 volt e bike go that has 3-12 volt 18 AH lead acid batteries ?

    • Jeff Kephart

      How long does it take for your grandmother to knit a scarf?
      There are MANY FACTORS beyond 36v at 18Ah and 500watts.
      What tires? Tire pressure? Surface you are on, how fat are you?
      What does bike weigh?
      Let me start with the controller (assuming brushed motor) how many amps
      max is the controller? How much does it draw on the flat?
      the “18ah” capacity is ONLY ACROSS 20 HOUR DISCHARGE TIME.
      Faster discharge=less Ah. So if you draw .9A for 20hrs that is 18Ah.
      if your bike only drew 9/10hs of 1 amp, you could ride for 20hrs.
      if your controller wide open, up a hill draws 30amps (1080w) your “18Ah”
      Will be more like 10Ah and you might get 20miles out of it.

      Putting this in car terms.
      Ah=side of petrol tank.
      Volts=max speed
      Tire pressure, width of tires, wind drag, vehicle weight. ALL are factors!

      This is what the thread is about, you can only measure and get your own
      results, mostly you can IGNORE the manufacturers statements of expected
      range, or assume you will get HALF.
      On my bike, with 1.9″ tires 26″ wheels, 96kg rider, 38kg weight and 20ah
      of SLA into a 450w motor, in HILLY area I got 19miles. (65 psi tires)
      Same bike, same tires, same etc, but FLORIDA where it is almost totally

      flat would do 40+ miles per charge.
      Watching the battery lights or an ammeter I found I could drop from wide
      open (19.8mph) to 15Mph and go from 9.8A to 6A, 19miles became 30.
      For just a bit less speed!
      Pedal and get this even wide open, or do even better.

      So sorry there is no “what will x and y get me?” simple answer or formula.
      My SLA bike used about 1Ah per mile on 24v system. In hilly city.
      My OTHER bike (250w hub motor, 28mm tires, 85psi, alloy frame)
      And LiMn 10ah batt got same range as the 20ah SLA bike, but req
      300% more peddle to make the hills (also was 1/3 the effort to pedal)
      I have hip and knee issues and is the reason I have an ebike. Some

      days I can pedal some, some days a lot, some days NONE. And this
      can change 10miles from home. The ebike gets me home!

      • Chaim Halberstam

        what a great answer, I wish I’dv read it before I attempted my own answer and comparison

    • K_2K

      36V * 18AH = 648 WH.
      648 WH / 20 WH/mi = 32.4 Mi.
      The math really is that simple. Assuming reasonable efficiency, speeds short of massive wind drag, and any other crazy miss-applications of equipment, it would be reasonable for a 180 lb. person to hope for near 32 miles with little or no assistance from the rider. As time goes on, the battery gets weaker, generally expecting 80% of the rated value near the end of life expectancy. So in three years or 500 charges, the same pack should give over 518 WH, for about a 25.9 mile range.

      Higher amp motor could get you there faster and slightly less than 32 miles mostly for increased power used on quick accelerations. Lower amperage would be slower and maybe slightly more miles for the same reason. Generally speaking 1 Watt is a unit of work the battery can provide you.
      As the author is trying to tell us, that makes what-hours more accurate for comparison of various bike ranges than the manufacturers’ mile estimates each assuming different levels of assist.

      I know I’m hitting one good size hill and another very steep hill on my 3 mile trip to work, so nothing will get the rated flat miles the way I use it.
      My Currie Trailz (rated at 10 miles based on 20 WH/mi.) easily pulled 8 miles over these hills with no help from me, and 15-18 miles with my help. Those lead-acid batteries had less than half their range after about a year each, and the brushed motor gave out in four years. (I know it’s brushed, I opened it up and saw the brushes, maybe the newer models were brush-less as stated above.)
      I’m ready to step up to a better model and Lithium batteries, and finding several reviewers agree 20 WH per mile is much better than just taking the maker at their word for distance.

      Of course, at $12000 for a bike that’s not street legal if I tweak it above 20 MPH without assist, the highway legal Zero is looking good. Even the $6800 Elio can go pretty far on the gas the difference can buy, AND gets us in out of the rain.

      • Jeff Kephart

        Where does this stated 20wh/mile come from? And how can it be applied to _EVERY_ ebike?
        Ok, my trailz has been measured at 24wh/mi in Pittsburgh (quite hilly).
        But my izip with 700c 85psi tires and 350w hub motor, alloy frame etc, needed less.
        I reject 20wh/mile being used as some kind of universal CONSTANT.
        The _ONLY_ way to guess the range of a bike will be to put a watt meter or at least Ammeter
        on it and ride it across a measured distance!
        (Ezip Trailz in my tests used around 9.5-10A wide open, and under 6A @ 3-4mph less)
        (so running 3/4 speed saves 33% on this drive system, 12mph vs 15-16)
        An ammeter visible by the rider can help stretch range. Cost is very small.

        • K_2K

          The number 20 is a fluke, just a number somewhat near measured truth.
          The watt is a mathematical definition of work. Move x grams of weight y meters of distance and you’ve done 1 watt of work. Do that repeatedly, and you’ve done some constant value of watt-hours of work to move 200 lbs of bike and man 1 mile in about 4 minutes. That’s an exact measurable amount well under 20 watt-hours. Subtract losses in friction, efficiency, transference, heat, etc, etc, in the end some number will start to show up over and over again. As controller, motor, and other technologies get better that number should go up some. Currently, if a battery is rated correctly the number needed in the battery just happens to be close to 20.
          If that’s not confusing enough, the power it takes to charge a battery to 1 watt-hour is also more than 1 watt-hour because of losses in the process of charging. Lucky for us the cost of that power such a small fraction of buying that same power in any type of fossil fuel.

          • Jeff Kephart

            To FURTHER confuse things (aka reduce the capacity
            on the label of batteries)
            Almost all battery figures quoted are driving the battery
            to FAR LOWER VOLTAGE than most controllers will
            consider DEAD and shut off.
            The usable Wh of say a 20wh pack might be 6!
            Because the 24v pack has dropped under the 19v or
            whatever the minimum for the PWM to run!

            So with this in mind, My so-called 40ah pack has ridden
            me 45mi and not quite been to shut off.
            Terrain as mentioned Hilly.
            Bike is close to 75lbs and rider 200lbs etc.

            What I’m saying is that unless you measure the bike
            and pack and come out with real world results, it is
            IMPOSSIBLE to say what it will do.

          • Chaim Halberstam

            I totally agree but many are looking for a precise measurable number that’s a constant accross a range, despite there being multiple different variables for each circumstance! So obviously that’s impossible to do.
            Also, aside from the differences between stated voltage and controller LVC setting, there is also the way the capacity is rated that can also confuse people.
            Lifepo4 at 24s will stay at an almost flat discharge curve around 80v thru 80% of range use, but the capacity is measured @72v (nom is minimum 76.4v) x the Ah of the battery. For my unit that’s a difference of 2160wh capacity versus the 2400wh that 80v 30ah would give, (mine is not 87.6v HOC, but @90.2v charged? For some unknown factory reasoning?
            My battery BMS immediately lowers it back to 86v upon the chargers disconnect, but I should probably buy a different smartcharger.)
            Even if using its nominal rating it’s 76v x 30ah to give 2,280wh but instead as I said they base it on 72v! Otherwise they’d have to admit it was only an 80v 28ah battery and imo (and theirs prob,)that doesn’t sound as good ;p

        • K_2K

          I err in not mentioning up front I also reject with you the constant of a watt-hour figure without including time in the distance, ie, at 15 mph you’re doing a lot less work that at 20 MPH, as you said much better and more accurately here.

      • Jeff Kephart

        Lead acid will be at SIXTY PERCENT at less than 300 charge cycles.
        Also, 3 18ah lead acids is going to make for a bike over 100lbs. (assumes steel frame)
        My currie with twin packs (that’s 4x 10ah 12v) is 94.

    • leo

      only way to know is try it and see

  • Peter Marcus

    This article assumed that the batteries even make their claimed capacity. My 960 watt-hour battery is really only 823 watt-hours. I have tested the range in the real world and I get 42 miles and that is with hills. If I pedal all the time and lower the motor assist, I can get as low as 7.5 watt-hours per mile and have a 109 mile range.

    • K_2K

      That’s a great point. I know “life expectancy” in the battery industry usually means how long it is expected to retain at least 80%, and we’re seeing most Lithium solutions rated to last 3 years. So one thing I’m checking on all the bikes and add-on kits I’m looking at is ( watt-hours X .80 ) / 20 = approximately how far I’ll be able to go on this battery after three years of usage.

  • Steven Cook

    meh, I’d rather buy a car for the same price as these bikes. bring the cost down to below $1000US and then we’ll talk.

    • Jeff Kephart

      would have to be a very cheap car.
      I have $1,000 in a bike that can do 70+mi on the flat with ZERO PEDAL.
      Recharges at $0.002266/mile (based on 10c/KWh)

      • Steven Cook

        I can buy three mopeds on Ebay for the same price as one of these E-bikes.

        • Jeff Kephart

          done the cost of running a moped?
          bet it’s a bit more than a quarter penny per mile.

  • Tom Miguel

    How much watt hours will a 5000 watt motor use at say 50 miles per hour? is there a calculation for speed/WH usage? or do we still use the 20watts per mile

    • Jeff Kephart

      WTF is “20 watts per mile”???
      A 50mph bike / 5KW motor is going to use a MASSIVE
      amount of energy. Wind resistance alone will make the
      needed energy square several times.
      Look at the prices of the factory electric MOTORCYCLES.
      (and their range)
      Or a TESLA car.
      I guess you are confusing watts with watt/hours?
      Or Kwh (thousands of watt hours?)
      50mph and 20Kwh per mile? Possibly.
      Betting you could spend $20,000usd in batteries to make this
      thing run 10miles @ 50mph.

      • Chaim Halberstam

        Well not quite $20k but maybe $2k if you want a lil range on your bike… I’m NO EXPERT as I’ve only recently go into E-bikes but as an example, my current build features a (mere 😉 1500w nominal leafmotor with a 16*4 winding, mated to an 18fet 4110 lyen edition Infineon controller and fed by a 72v 24s1p 30ah lifepo4 prismatic (soft pouch) A123 3c-8c high discharge cells, battery pack with a 60-120a BMS. Although I currently have it limited to 30mph (much longer range and no heat issues) I could quite easily re-program the controller for the stated 50mph and I’m confident my battery would definitely triple that 10 mile estimate, despite wind resistance at higher speeds. I should mention that my pack cost LESS than $1k delivered (but weighs 17kilo) so centering and balancing that weight accurately (and low as poss) on your frame is a priority (And although my bike might look like one, it’ll never be jumped like a stealth, which has amazing engineering IMO.) So if 50 mph (not higher) is the goal, for a city commuter one doesn’t need a 5000w battery power sucking, monster Cromotor (or bigger!) run @72v or higher to acheive that. No, imo, a more modest 1500w unit (Leaf’s best is about 90% efficient @48v) mated to a quality, min 12 fet (reprogrammable) controller is the way to go.

        • leo

          youve really done your sums . ive thought about building a more powerful bike and have looked at the hub motor kits on ebay but there seems to be so many options. was thinking maybe 750w and use the zippy batteries. maybe 6s 22.2v 20000mah , would prob need two in series. what would you suggest? where can you buy a 24s battery? ive only seen up to 6s

          • Chaim Halberstam

            Well yes and No… Yes, I did my sums for the build costs, but more importantly for the performance figures I’m quoting, they come from my real world experience, acquired in testing my “build,” and was done with a calibrated Cycle Analyst V3 DP version. After the first 100 miles of mixed terrain, and using a 3sp switch plugged in to the aux pot for on the fly power adjusment, but used mainly on setting 1 (28a max) I average 43.4 wh/mile with NO PEDDLING.
            On using setting 2 far more (46a max) it rises to 55-67 wh/mile and my max speed in testing is 61 mph (135lb load, me 😉
            And setting 3, (62a max) is only used for initial 10-15 second acceleration bursts @lights.
            I wouldn’t give a wh/mile reading on 3, as it would probably overheat the hubmotor above 150°C before very long, since at the 80v charge level on my lifepo4 battery, (62a-65a Inc phase) would equal 5000w draw on a max 2kw continuous motor, even for bursts you’ll have to let the motor recover and help it cool, staying on setting 1.
            Your best bet to learn what to do to upgrade, and also gain general Ebike knowledge and insight, is to check out the Endless Sphere forum, ALL ur questions (have already been asked,) and will be answered there.
            As for where to buy a 24s battery? Google your requirements, and you’ll find plenty of suggestions. Mine came from Victpower factory in China and cost almost $1k delivered to the US (by air) and a small customs duty… alternatively just make your own, you don’t need 24s, just 3 of those 22.2v 20ah units, would give you 18s 20ah … I say that because 24s 88.8v (might have) an HOC, (or hot off charger,) voltage that exceeds the 100v max cap limit, of the mosfets in the controller, but it’s your choice obv.
            I DO Reccomend a pretty built factory lithium batt with a BMS installed, (rather than cheaper, cobbled together, less safe rc lipo power,) but again! it’s ALL your choice, so good luck if u go ahead with a build, and chk out that ES forum I mentioned earlier.

          • leo

            Hi there thanks for your reply 🙂 as it happens I was offered an almost new pro rider wayfarer folding bike. It has 36v 10a battery and 250w motor for 300 pounds and I bought it. I get about 55 miles on a charge using motor to help on the hills doing about 12 mph. I know that’s quite slow but I love cycling long distance and this just gives me the wee help I need. Only thing I would like to get a bigger capacity battery, maybe to get 100 miles would need to be 20a 37v where’s a good place to get that do you think?

          • Jeff Kephart

            Battery may cost almost what you paid for the bike.
            You’ll need to rig some way to break out the power input from the socket the
            factory battery jacks into. Or at bare minimum figure a way to TEE the power
            to the motor controller and disable or remove the factory pack when the aux
            pack is in use. IMO get a 20-30Ah 36v pack and remove the factory one and
            leave it at home for a quick ride to the shop etc.
            Best bang for the buck is LiFeP04, they are all over the place (fleabay etc)
            you need 12s (twelve in series) for 36v. You also want a BMS (battery
            management system). This board has sense wires to each section of the 12
            series pack and operates in charge AND discharge (always in circuit) to
            prevent imbalance between the sections that would ruin your 200quid battery!
            Spend the few extra quid to get LiFeP04 not Li-Po, LFP is inherently incapable of melting down (and taking bike and maybe YOU with it).
            Li-Po (aka li-poly) can shoot flames like a cutting torch and even explode.
            Whereas there is a youtube where a guy shoots a NAIL GUN into a 30Ah
            prismatic LFP and it simply emits steam for 40min.

          • leo

            Hi is it 12s not 10s? Is 12s not about 44v?

          • Jeff Kephart

            It is not calculated by PEAK voltage.
            8 cells (or banks of cells) is 24v, even though it charges to 29.6 (also, running
            them up to 4.4v per is hard on them, if you want max life use 12s to make 36v)

  • James Mills

    What would be a tipical range of a 1000w motor with a 48v 20ah battery? If anyone could give me rough ideas thanks

    • Jeff Kephart

      Your question is TYPICAL of those that have not even read this thread, let alone done any other research.
      So I’ll say 10 feet, or 10 miles, or maybe 20……. READ THE THREAD

  • Hhsyagavga

    I like the time you took to write a review. On the specialized bike you are severely incorrect about EB real life range. I get 20 miles and my battery is at 50%. That’s on the highest mode and averaging 20mph. The roads I ride are streets with a few up hills over freeway overpasses

  • leo

    what a great article , i use the zippy batteries in the picture above on my old yamaha xpc26 and it works brilliantly, zippy 8000mah 22.2v gets me about 15 miles on very hilly ground. the only thing is these old bikes give you very little assistance, means i stay warm and dont get fat while cycling 🙂

  • Knapweed

    What makes a motor as efficient as 15 WH per mile as opposed to 20 WH per mile. How can you tell which is which apart from actually testing the bike in the real world?

    • spinningmagnets

      Making the laminations in the motor thinner and appropriately sizing the motor to the anticipated load, also keep the magnet speed up in relation to the number of meters of distance travelled. Below 20-MPH, the weight of the system has a big effect on efficiency, above 30-MPH aerodynamics play a huge role that is often neglected.