E-bike speed vs range comes down to one unforgiving piece of physics: the power needed to push through the air rises with the cube of your speed. Nudge your speed up by a quarter and the energy you burn per kilometre can climb far more than a quarter, so a faster e-bike drains its battery noticeably sooner. Your range is simply your battery’s watt-hours divided by your watt-hours per kilometre, and that Wh/km figure climbs steeply the harder you push the pace.
The upside for Sydney riders is that the NSW-legal 25 km/h pedal-assist limit sits close to the efficiency sweet spot, so a legal e-bike is naturally set up to go a long way on a charge. Here is how the numbers actually work, grounded in the engineering tools from Grin Technologies (ebikes.ca), and how to squeeze more kilometres out of the same battery. At Cyberbikes in Leichhardt we get asked “why is my range lower than the brochure?” constantly, and the honest answer is usually speed.
E-bike speed vs range at a glance
| Riding speed | What’s using the energy | Effect on range |
|---|---|---|
| Up to ~15 km/h | Mostly rolling resistance and the drivetrain | Very efficient, longest range |
| ~25 km/h (NSW assist limit) | Rolling resistance plus rising air drag | Efficient sweet spot for commuting |
| ~32 km/h | Air drag now dominates | Range drops off clearly |
| 40 km/h+ | Air drag is almost everything | Range falls away fast |
Why does going faster use so much more energy?
At a standstill the air is no problem, but as you speed up it fights back hard. Aerodynamic drag force grows with the square of your speed, and because power equals force times speed, the power needed to overcome that drag grows with the cube of your speed. Double your speed and you need roughly eight times the power just to beat the air. This is why Grin’s motor simulator shows the load line, the power required to keep moving, rising “quite steeply at increasing speeds” once you are past a gentle cruise.
How much air you have to move depends on your shape. ebikes.ca measures this as CdA, your effective frontal area, which ranges “from 0.2 for a fairly streamlined recumbent up to 0.8 for a wide upright mountain bike with a puffy jacket”. A big upright riding position is comfortable, but it is also a sail, and at 30-something km/h that sail is doing most of the work of emptying your battery.
Drag versus rolling resistance
The other force holding you back is rolling resistance, which ebikes.ca expresses as Cr, “from about 0.004 for a high pressure road slick, up to 0.012 for a low pressure knobby wheel”. Rolling resistance stays roughly constant as you speed up, so at low speeds it is the main cost of moving. Air drag, by contrast, keeps growing, and somewhere around a brisk cruising pace it overtakes rolling resistance and never looks back. That crossover is the reason a relaxed ride sips power while a fast one gulps it.
How to work out your real e-bike range
Range is refreshingly simple maths. ebikes.ca defines consumption as your Wh/km, “a direct measure of how much battery energy you use per distance travelled”, and range as the distance a full charge delivers “based on the available battery capacity and not the nominal amp-hours”. So:
Range (km) = usable battery watt-hours ÷ energy use (Wh/km)
Take the 2026 Cyberbikes Centauro, which runs a large 48V 25Ah (1200Wh) Samsung battery. A gentle commuter sipping around 10-12 Wh/km could see roughly 100km, while the same bike ridden hard at 12-14 Wh/km and above will land well short of that. It’s the exact same battery and motor, the only variable is how fast and hard you ride. If you want the full picture of what determines pack capacity, our definitive guide to e-bike batteries breaks down volts, amp-hours and watt-hours.
How to get more range from the same battery
Because speed is the biggest lever, the fastest way to add range is simply to ease off the pace, especially into a headwind. Beyond that, shrink your CdA by getting lower and narrower when it’s windy, pump your tyres to a sensible pressure to cut that Cr number, drop unnecessary cargo weight, and use a lower assist level on the flat so the motor isn’t over-delivering. Temperature matters too, which is why cold snaps sap your kilometres, we cover that in why e-bike range drops in winter. For a typical Inner West commute, a rider who cruises at 25 km/h rather than sprinting everywhere will often see 30-40% more range from an identical charge.
Does the 25 km/h limit actually help your range?
Whether or not you agree with the 25 km/h assist cap, and Cyberbikes has plenty to say about that debate, it does keep legal e-bikes parked in an efficient zone. Because drag hasn’t yet run away at 25 km/h, pedal-assist bikes that cut motor help at the limit tend to return strong real-world range, which is part of why they make such practical commuters. Push a bike past the cap and range is one of the first things you sacrifice.
Watch: the 25 km/h debate, explained
Speed is the master dial for both how quickly you arrive and how far you’ll get. This short Cyberbikes video digs into the 25 km/h assist limit that shapes how most Australians ride:
Frequently Asked Questions
Does going faster really use more battery on an e-bike?
Yes, and more than you would expect. At any real riding speed most of your effort goes into pushing air aside, and the power needed to overcome aerodynamic drag rises with the cube of your speed. So a small jump in speed means a large jump in watt-hours per kilometre, which is why a faster e-bike empties its battery sooner.
How do I calculate my e-bike’s real range?
Divide your battery’s usable watt-hours by your energy use in watt-hours per kilometre. For example, a 1200Wh battery at 12 Wh/km gives roughly 100km, while the same battery at 20 Wh/km gives about 60km. Your Wh/km depends mostly on speed, rider weight, terrain, wind and tyre pressure.
What speed is most efficient on an e-bike?
Lower speeds are always more efficient, but for most commuters the practical sweet spot is around the 25 km/h NSW pedal-assist limit, where aerodynamic drag is still manageable. Riding much faster pushes energy use up steeply, so easing off even a few km/h noticeably extends your range.
Want big real-world range? Ask us about the Centauro’s 1200Wh battery. Come in for a test ride at Cyberbikes, 281 Parramatta Road, Leichhardt, call us on 0491 794 668, or browse the Centauro online and ask about rent-to-own from $99/week.
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