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 electricbike.com. 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)
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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.
This article originally appeared on https://www.electricbike.com/watt-hours/