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What really decides your e-bike range

Battery capacity in watt-hours sets the size of the fuel tank, but the range you actually get depends far more on how hard the motor has to work. The same pack can deliver double the distance in eco mode on the flat that it manages in boost up a hill.

Watt-hours set the ceiling

Range starts with energy, measured in watt-hours (Wh), which is voltage multiplied by amp-hours. A 500 Wh pack holds 500 Wh of energy. A rough rule of thumb on a mid-drive is that a rider draws somewhere between 7 and 20 Wh per mile depending on effort, so a 500 Wh pack might cover anywhere from 25 to 70 miles. The pack size is the ceiling, not the answer.

Assist level is the biggest lever

The single largest factor a rider controls is the assist level. Eco or tour modes add a modest percentage to your own effort and sip energy; turbo or boost modes can add three or four times your pedalling power and empty a pack quickly. Riding one level lower than you think you need is the most effective way to extend range on any given ride.

Weight, terrain and the environment

Every extra kilo of rider, luggage or bike costs energy on every climb and acceleration, so a loaded cargo bike drains a pack far faster than a light commuter. Hills, headwinds, soft or rough surfaces and frequent stop-start riding all raise the load. Cold weather reduces usable capacity because lithium cells deliver less energy when cold, and under-inflated tyres add rolling resistance. None of these change the watt-hours in the pack, but all of them change how many miles those watt-hours buy.

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Sources: Bosch eBike Systems, range assistant and range factors