To check out your own cycling theoretical power needed taking into account a number of variables, check out the Penn State Bicycle Power Calculator. If you need to get an accurate measure of your power output while cycling, we recommend a cycling power meter.
Remember that your ebike with battery pack will weigh from around 40 -60 pounds!
Note for instance that in theory, a 2% slope more than doubles the power required to maintain speed.
Electric Assist Bikes - Everyday needs
The above numbers show ideal, theoretical and racing type applications. Every day riding
is not ideal. You might have low tires, rubbing brakes, towing a trailer, or bearings that need adjustment. It might be blowing or you may need to get up a 5% grade.
In reality, the lower output ebikes will struggle in many practical situations. This is could be why some people in the UK have been resorting to "tuning", their ebikes.
250 Watt motors are enough for pedal assist applications in average, normal riding conditions.
350-500 Watt motors will expand your range of riding options and could include hills and other demands on the motor. You will still need to assist in the pedaling.
If you encounter many steep hills and other tough road conditions, and you want to
maintain a reasonable speed, you will want to head for the 750 Watt motors, and
above where legal. It is import to notice that as motor power goes up,
so does power use.
Check the next page for graphs showing Ebike power needs.
EBike Energy vs Regular Bike Energy and Food
It seems intuitive that the electric bike would need more energy to ride than a
conventional bike. However, the reverse is true for most store shopping people.
A life cycle analysis shows that eBikes actually take some two to four times less energy than a cyclist riding a regular pedal bike.
The difference lies in the energy required to produce and distribute food. It sounds
odd, but you can read for yourself here.
Despite the intuitive sense that electric bikes would require more resources than
regular bikes, life-cycle analysis shows that they actually consume 2-4 times less
primary energy than human riders eating a conventional diet. This conclusion is
largely due to the considerable amount of transportation and processing energy
that is associated with our western food system.
Human power energy table
Electric bicycles should probably be called the electric assisted bicycles. Most electric bikes are not like electric motorcycles or scooters. Except for a few high powered rides, most ebikes need some degree of pedal assist to get down the road. Its all about energy, or power as measured in Watts. Here's why, and read this before you buy!
Electric bikes in the real world
In ideal conditions, you could zip along on your ebike like it was a motorcycle. Not
that you can't zip along, but in the real world, ideal conditions are hardly ever met. There are always some restrictions.
A few things that control ebike use:
Laws - most countries limit legal ebike power
Terrain - steep hills take a lot more power than flat ground
Speed - the faster you go, the bigger the motor you need
Wind - riding 10mph/kph into a 10mph/kph wind doubles the work
Weight - most ebikes have weight limits, 250lbs/114kg is common
Towing - towing a trailer takes more power
Acceleration - fast starts use a lot of power
Battery - you need a good strong battery to match the motor power
Maintenance - ebikes need good upkeep to be most efficient - air your tires!
Electric bike motor ratings
Electric motors are generally rated by the power that they use at two points: Watts at continuous and peak power. Continuous power is the Watts you use cruising along about half throttle, peak is Watts wide open under full current.
Actual motor power output depends on a number of factors like battery power and controller current supply. Manufacturers tend to use the continuous power rating.
How much power you might use
Your cycling power output can be measured in Watts, just like an electric motor. The table below shows some approximate power uses. Keep in mind that these values are approximate for illustration, and can vary considerably.