Gradient is the biggest force in the equation
Climbing power is beautifully simple: force equals mass × gravity × sin(angle), and power is that force times your speed. A 100 kg rider-and-scooter on a 10% grade faces about 98 N of gradient force. Holding 20 km/h against it takes 545 W at the wheel before you add rolling resistance, drag or drivetrain losses.
Compare that with the same rider on the flat at 20 km/h, who needs about 175 W at the wheel for rolling resistance and drag combined. Add the hill and the total passes 700 W — four times the demand, from a gradient you can barely see. This is why scooters that feel lively on the flat crawl up bridges and multi-storey car park ramps.
Percent grade, degrees and what real hills look like
Grade as a percentage is rise over run: a 10% grade climbs 10 m over 100 m travelled, which is 5.7°. Road signs use percent, mapping apps use percent, and most scooter specs quote "max incline" as a percentage — often optimistically, measured at walking pace with a light rider.
For reference, a typical residential street is 3–6%, a steep city hill is 8–12%, San Francisco's notorious blocks run 15–25%, and a wheelchair ramp is capped at about 8%. Anything above 15% is a genuine engineering problem for a hub motor: current climbs, RPM falls, and cooling airflow disappears exactly when you need it most.
Watch the amps, not just the watts
The current figure is the one that kills components. Power divided by pack voltage gives battery amps, and on a 36 V system a 900 W demand is 25 A — beyond the continuous rating of many stock BMS boards and a lot of 10-cell parallel packs. Sustained over a long climb, that shows up as voltage sag, thermal cutbacks or a tripped BMS halfway up.
Two practical rules. Keep sustained climbing current below the pack's continuous rating with 20% headroom, and treat any climb longer than about 90 seconds as a thermal event: pull over and let the motor cool if it smells hot or the deck feels warm. Higher-voltage systems help here, because the same power at 60 V draws 40% less current than at 36 V.
What real gradients look like
Percent grade is rise over run. Road signs, mapping apps and scooter specifications all use it, while degrees show up in engineering drawings. The two are close at shallow angles and diverge quickly, which is why a "20°" claim is nearly double a "20%" one.
| Grade | Degrees | Where you find it |
|---|---|---|
| 2% | 1.1° | Barely perceptible; motorway gradient |
| 5% | 2.9° | Noticeable on a scooter; typical bridge approach |
| 8% | 4.6° | Maximum for a wheelchair ramp; steep street |
| 10% | 5.7° | Steep city hill; most scooters slow markedly |
| 15% | 8.5° | Multi-storey car park ramp |
| 20% | 11.3° | San Francisco residential blocks |
| 30% | 16.7° | Among the steepest paved roads anywhere |
Sizing a motor for the hill, not the flat
Most buying decisions get made on flat-ground top speed, which is the least demanding thing a scooter does. If your commute has a climb, size for it: work out the power at your real gradient and speed, then check that the figure sits inside the motor's continuous rating with room to spare.
Watch the current column too. On a 36 V system, 900 W is 25 A — beyond the continuous rating of many stock battery management systems and 10-cell parallel groups. The same 900 W at 60 V draws 15 A, which is why higher-voltage systems climb better even at identical power. If you are designing the pack yourself, the pack calculator will tell you whether your parallel count can supply what this page is asking for.
Questions riders actually ask
What gradient can a 350 W scooter climb?
With a 75 kg rider, a 350 W continuous motor will hold a walking-to-jogging pace up about 8–10%, and will struggle above 12%. Manufacturers who claim 20% for a 350 W scooter are quoting a brief burst on peak power with a light rider, not something you can ride to work every day.
Why does my scooter slow to a crawl on hills but the motor is not at full throttle?
It probably is at full throttle electrically — the controller has hit its current limit. Once current is capped, the motor produces a fixed torque, and on a steep grade that torque only balances gravity at low speed. The throttle position stops mattering; the current limit is doing the deciding.
Does standing further forward help on climbs?
On a rear-hub scooter, shifting weight back slightly improves traction on wet or loose surfaces, but it does not change the power required. What genuinely helps is carrying less, keeping tyres properly inflated, and building speed before the hill so you arrive with momentum.
How do I convert max incline percentage to degrees?
Degrees = arctan(grade ÷ 100). So 10% is 5.7°, 15% is 8.5°, 20% is 11.3° and 30% is 16.7°. The two numbers are close at shallow angles, which is why people mix them up, but they diverge quickly — never assume a "20°" claim means 20%.
Is regenerative braking worth anything on a hilly route?
It recovers roughly 5–10% of your energy in stop-start city riding and a bit more on long descents, but the electric brake on most scooters is weak by design to protect the controller. Treat regen as brake-pad savings and a small range bonus, not as a solution to a hilly commute.
What about e-bikes and cargo bikes?
The maths is identical — only the drag area and rolling resistance change. Set drag area to about 0.4 m² for a seated cyclist and remember to include cargo and child weight in total mass. A 250 W legal e-bike motor plus 150 W of pedalling behaves like a 400 W scooter on the hill.