What does power mean in the context of drive units?

Power is measured and indicated in watts (W). It is responsible for how fast you can ride: The higher the power, the higher the speed you can ride at constantly. This is particularly noticeable when riding uphill, as eBikes have a legal speed limit of 20 mph. To ride 20 mph on the flat, < 250 W is usually sufficient (depending on the surface, bike/rider weight, wind conditions). For eBikes, we distinguish between rated continuous output and maximum power.

Rated continuous output

Rated continuous output describes the mechanical power that your drive unit can provide continuously without the components overheating or being damaged. Under EU law, the mechanical rated continuous output is limited to 250 W – this applies to all eBikes and eBike motors.

Maximum power

For eBikes, we distinguish between rated continuous output and maximum power. Maximum mechanical power (also called peak power) describes the maximum power that the motor can call up for a short time under optimal conditions (e.g., sufficiently charged battery), for example on climbs.
The duration depends on several factors, such as the cooling of the eBike components, the charge level of the battery, and the outside temperature. By calling up the maximum power, the eBike components continue to heat up, which means that, to protect the components, the maximum power cannot be called up permanently.

Power-to-weight ratio

The power-to-weight ratio indicates the ratio of the maximum power to the drive unit weight. It indicates the maximum horsepower provided per pound and serves as a comparative value between different drive units. A higher power-to-weight ratio can lead to a higher speed, as weight plays a role for this. Weight is a significant component of riding resistance, which means that a higher final speed can be achieved with the same power and a lower weight. eBike riders notice this primarily on steep ascents and on mountains, as weight plays an increasingly significant role in riding resistance with increasing gradient. However, the total weight (eBike and rider) should always be considered.

Relationship between power and speed

The faster you ride, the (disproportionately) greater the riding resistance becomes. This means that at a higher speed, more power is required to maintain that speed. If you ride with a cadence of 70 rpm at 9 mph, you need less pedal force than if you want to ride at 20 mph with a cadence of 70 rpm.