What determines real-world e-bike range?

Aerodynamic drag scales with velocity cubed

Speed is the dominant consumer of battery energy above 15 mph (24 km/h). Aerodynamic power loss scales with the cube of speed (v³). Cruising at 28 mph requires roughly 2.5 times the propulsion power needed at 20 mph, effectively halving battery range. Lowering rider posture from upright (CdA ≈ 0.65 m²) to an aerodynamic tuck (CdA ≈ 0.32 m²) reduces wind resistance by up to 50%.

Hills and total payload mass

Overcoming gravity requires direct mechanical work equal to mass × gravity × vertical climb rate (P = m · g · v · sin θ). Climbing a 6% grade at 15 mph demands roughly 350W to 450W of continuous power purely against gravity. Rider weight, heavy cargo, and a heavy bike significantly penalize hill range while having relatively minor impact on flat cruise.

Rolling resistance and tire selection

Tire compound, tread profile, and inflation pressure dictate rolling resistance (P = Crr · m · g · v). Wide, under-inflated knobby mountain or fat-bike tires (Crr ≈ 0.007–0.009) dissipate an extra 4 to 8 Wh per mile compared to supple, high-pressure semi-slick commuter tires (Crr ≈ 0.0035–0.0045).

Ambient temperature and battery voltage sag

Lithium-ion cells suffer higher internal impedance at lower temperatures. When cell temperatures drop below 40°F (5°C), increased voltage sag under load triggers earlier controller low-voltage cutoffs, reducing deliverable watt-hours by 15% to 25%. In sub-freezing winter riding (20°F / -7°C), usable energy can drop by up to 35% compared to room temperature.

Pedal assist is a range multiplier

An alert cyclist delivers between 75W and 150W of steady mechanical effort. Because flat cruising at 20 mph typically requires 220W to 280W total, active human pedaling supplies 30% to 55% of the total propulsion energy, effectively doubling or tripling real-world range compared to throttle-only operation.

Rule-of-thumb watt-hours per mile

Plan battery energy budgets with realistic consumption benchmarks:

• Flat pavement, 18–20 mph with moderate pedaling: 12–16 Wh/mi (7.5–10 Wh/km).
• Flat pavement, 20 mph throttle only: 20–25 Wh/mi (12.5–15.5 Wh/km).
• High-speed 28 mph Class 3 cruising: 35–45 Wh/mi (22–28 Wh/km).
• Steep hilly terrain or strong headwinds: 45–65+ Wh/mi (28–40+ Wh/km).