How many watts does an e-bike need for hills?
To hold 10 mph up a 10% grade on throttle, a 180 lb rider on a typical 63 lb e-bike needs about 850 W from the battery; a 5% grade takes about 430 W. So a 750 W hub motor (about 1,310 W peak) climbs a 10% hill at about 14 mph, a 500 W hub at about 12 mph, and a 250–350 W motor at about 8–9 mph unless you pedal hard.
Battery watts needed to hold a speed uphill
Throttle only (no pedaling), 180 lb rider, typical 750 W hub commuter (63 lb), paved road, no wind, from our physics model. This is power drawn from the battery, including motor losses:
| Grade | 8 mph | 10 mph | 12 mph | 15 mph |
|---|---|---|---|---|
| 3% | 225 W | 290 W | 364 W | 496 W |
| 5% | 333 W | 425 W | 527 W | 701 W |
| 8% | 526 W | 668 W | 820 W | 1,071 W |
| 10% | 669 W | 847 W | 1,036 W | 1,344 W |
| 15% | 954 W | 1,204 W | 1,464 W | 1,879 W |
A 5% grade is a typical highway ramp or a steady neighborhood hill; 10% is steep; 15% is the steepest pitch most riders meet on city streets. Climbing power rises with weight and with speed: at 10 mph up a 10% grade, relaxed pedaling (about 35 W from your legs) lowers the battery draw to about 794 W, and a 250 lb rider needs about 1,072 W.
What each motor size actually does on a hill
Medians across the bikes on sale we track whose brand publishes peak power (and, for hub motors, torque), with a 180 lb rider. "Steepest at 8 mph" is the steepest grade the bike can hold at 8 mph:
| Motor | Bikes | Peak power | Speed up 10%, throttle | Steepest at 8 mph, throttle | …with moderate pedaling |
|---|---|---|---|---|---|
| 250–350 W mid-drive | 7 | 600 W | 9 mph | 11% | 13% |
| 250–350 W hub | 6 | 650 W | 8 mph | 10% | 14% |
| 500 W hub | 5 | 1,092 W | 12 mph | 16% | 18% |
| 750 W hub | 28 | 1,310 W | 14 mph | 20% | 23% |
The nominal rating on the box (250, 500, 750 W) is a continuous rating; on a short hill the controller lets the motor draw its peak power for a minute or two. That is why a 750 W bike can pull the 1,036 W a 10% grade takes at 12 mph. On a long climb the motor heats up and the controller may cut back toward its nominal rating.
Mid-drives look weaker here because the table is at a fixed 8 mph. Shift down and slow to 5–6 mph and a 250 W mid-drive with a rider pedaling hard climbs grades a 250–350 W hub can't, because the bike's gears keep its motor spinning fast. Hub motors also lose efficiency on steep grades, up to about 18% more energy per climb in a bench study (see our methodology).
How much power do you need?
- Gentle hills (up to 5%): any e-bike, including 250 W, holds 10 mph or more.
- Steep city hills (8–10%): a 500 W hub or a mid-drive with some pedaling; a 750 W hub if you want to stay on throttle at 12–14 mph.
- Very steep (12–15% and up), heavy riders or cargo: a 750 W hub with high torque (80 Nm or more) or a mid-drive in a low gear.
See the best e-bikes for steep hills ranked by climbing ability, or set the grade, your weight and your bike in the simulator. Every bike page shows its climbing speed at 5, 10 and 15%.
Common questions
Is a 500 W e-bike enough for hills?
For most city hills, yes. The 500 W hub bikes we track peak at about 1,092 W and hold about 12 mph up a 10% grade on throttle with a 180 lb rider. They can hold 8 mph up to about a 16% grade without pedaling.
Is 750 W better than 500 W for hills?
Yes, mostly through higher peak power and torque: the 750 W hubs we track peak at about 1,310 W and climb a 10% grade at about 14 mph on throttle, against 12 mph for 500 W hubs. They are also heavier (median 75 lb), which costs range everywhere else.
Why does a 250 W mid-drive climb so well?
A mid-drive drives the chain, so in a low gear the motor stays in its efficient speed range on a steep hill while the bike slows down. A hub motor is geared to the wheel and loses torque and efficiency as the bike slows. Mid-drives reward pedaling: they multiply what you put in rather than replacing it.
How much more power does a heavier rider need on hills?
Climbing power rises in proportion to total weight. At 10 mph up a 10% grade, a 250 lb rider needs about 1,072 W from the battery on throttle, against 847 W for a 180 lb rider.