What drains an e-bike battery most is the assist mode, followed by wind, climbing and temperature. Weight, speed and tires matter, but much less. With a 500 Wh battery and our calculator’s assumptions (a 165 lb rider, a 53 lb bike, rolling terrain, 12 mph and 64 °F), tour mode gives about 55 miles (89 km); turbo, 38 miles (61 km); and eco, 86 miles (139 km). As a rule of thumb, on rolling terrain in a middle mode an e-bike uses about 8 Wh per mile (5 Wh/km); in the mountains in turbo, more than twice that.
Bosch eBike Systems sums it up in its battery guide: there’s no single range figure, because range depends on terrain, tires and riding mode. Here’s how much each factor weighs, with numbers.
How e-bike range is calculated
The math is simple:
Miles = usable Wh in the battery ÷ Wh the bike uses per mile
- Wh (watt-hours) is the energy the battery stores. It’s voltage times amp-hours: a 36 V, 13.9 Ah battery holds about 500 Wh. That’s the number to compare batteries by, not Ah.
- Usable Wh: you don’t get 100%. The system keeps a reserve and the battery loses capacity over the years. Our calculator uses 90% of the rated figure: 450 usable Wh from a 500 Wh battery, a bit less in the cold.
- Wh per mile: what the motor draws from the battery to help you. It depends on how much power the bike needs (air, rolling resistance and grade) and how much of it the motor supplies (the assist mode).
Our model cuts the motor off at 15.5 mph (25 km/h), the limit for pedelecs in Europe. In the U.S., Class 1 and Class 2 e-bikes assist up to 20 mph and Class 3 up to 28 mph, so if you cruise above 15.5 mph your real consumption will be higher than the figures here. What the classes mean and where you can ride each one is covered in e-bike laws.
The assumptions behind every example
All the figures in this guide come from the same model as the e-bike range calculator and the e-bike range by battery chart, with their default values, so they match:
- 223 lb (101 kg) total: a 165 lb (75 kg) rider, a 53 lb (24 kg) bike and 4.4 lb (2 kg) of gear.
- 12 mph (20 km/h) cruising speed, no wind, at 64 °F (18 °C), with commuter tires and an upright position.
- You put in 100 W with your legs and the motor adds 55% in eco, 120% in tour, 200% in sport and 300% in turbo, up to 450 W.
- Terrain: flat, 10 ft of climbing per mile (2 m/km); rolling, 63 ft per mile (12 m/km); mountain, 132 ft per mile (25 m/km).
When an example changes something (a different battery, tire or temperature), we say so.
Assist mode: the biggest drain
The motor multiplies what you put in. In eco it adds roughly half your effort; in turbo, up to three times more, according to the spec sheets of motors like the Bosch Performance Line. More help means faster climbing, but also more consumption.
Estimated range on rolling terrain (63 ft of climbing per mile):
| Battery | Eco | Tour | Sport | Turbo |
|---|---|---|---|---|
| 400 Wh | 69 mi (111 km) | 44 mi (71 km) | 35 mi (56 km) | 31 mi (49 km) |
| 500 Wh | 86 mi (139 km) | 55 mi (89 km) | 43 mi (70 km) | 38 mi (61 km) |
| 625 Wh | 108 mi (174 km) | 69 mi (111 km) | 54 mi (87 km) | 48 mi (77 km) |
| 750 Wh | 129 mi (208 km) | 83 mi (133 km) | 65 mi (105 km) | 57 mi (92 km) |
On rolling terrain, consumption goes from 5.1 Wh/mile in eco to 11.6 Wh/mile in turbo (3.2 to 7.2 Wh/km): more than double. These figures are the midpoint of a range; in practice, hard starts, gusty wind or low cadence can take off another 20%. The e-bike range by battery chart extends these figures to 545 and 800 Wh and to flat and mountain terrain, with the range for each.
Climbing: going up costs energy
On a climb, most of the power goes into lifting you and the bike. With 223 lb (101 kg) total, climbing 330 ft (100 m) takes about 27.5 Wh of mechanical energy, before motor losses, and you supply part of it. You get nothing back on the descent: e-bikes don’t recharge the battery when braking.
With a 500 Wh battery:
| Terrain | Climbing | Eco | Tour | Turbo |
|---|---|---|---|---|
| Flat | ~10 ft per mile | 111 mi (178 km) | 72 mi (115 km) | 53 mi (85 km) |
| Rolling | ~63 ft per mile | 86 mi (139 km) | 55 mi (89 km) | 38 mi (61 km) |
| Mountain | ~132 ft per mile | 60 mi (97 km) | 39 mi (63 km) | 27 mi (43 km) |
In the mountains, if you also run knobby tires, consumption rises to 8-18 Wh/mile (5-11 Wh/km) depending on the mode. A 25-mile (40 km) e-MTB ride with 3,280 ft (1,000 m) of climbing in tour mode uses about 280 Wh with commuter tires and about 310 Wh with knobbies: more than half of a 500 Wh battery.
Wind, cold, weight, speed and tires
Starting from the 500 Wh battery in tour mode on rolling terrain, which gives about 55 miles (89 km), here’s how range changes when a single factor changes:
| Factor | Change | Range |
|---|---|---|
| Headwind for the whole ride | 0 → 9 mph (15 km/h) | 55 → 36 mi (89 → 58 km) |
| Temperature | 64 °F → 32 °F (18 → 0 °C) | 55 → 45 mi (89 → 73 km) |
| Total weight (rider + bike + gear) | 179 lb → 267 lb (81 → 121 kg) | 63 → 49 mi (101 → 79 km) |
| Cruising speed | 9 → 15.5 mph (15 → 25 km/h) | 60 → 50 mi (96 → 81 km) |
| Tires | Road → knobby MTB | 59 → 48 mi (94 → 77 km) |
What surprises people most is the wind. A moderate 9 mph headwind takes more than a third off your range on the stretch where it’s against you, because air resistance grows with the square of relative speed. On an out-and-back ride, the tailwind home doesn’t fully make up for it: with a 9 mph headwind out and a tailwind back, the battery gives about 48 miles (77 km) instead of 55.
Speed matters less on rolling terrain because you go slower on the climbs anyway. On the flat it shows more: with 500 Wh in tour mode, at 12 mph (20 km/h) you get about 72 miles (115 km) and at 15.5 mph (25 km/h), about 56 miles (90 km).
Cold weather
Lithium-ion batteries deliver less energy when they’re cold. Bosch says in its guide that storing the battery between 32 and 50 °F (0 and 10 °C) doesn’t harm it, but that a cold battery delivers less power, and advises bringing it into a heated room on very cold days and waiting until it’s at room temperature before riding. With our assumptions, at 32 °F (0 °C) range drops by about 18% (from 55 to 45 miles) and at 14 °F (−10 °C), by more than a third (36 miles). The loss is temporary: once the battery is back at room temperature, it recovers its performance.
Tires and pressure
A knobby mountain bike tire has much more rolling resistance than a slick: with the same assumptions, going from a road tire to a knobby takes off more than 10 miles. On a city e-bike, low pressure does the same thing: at 15 psi (1 bar) below the recommended pressure, the tire deforms more and wastes energy. Check your pressure every week with the tire pressure calculator, which has a dedicated e-bike mode because they’re heavier.
Real-world examples
A 7.5-mile (12 km) city commute each way. 15 miles (24 km) a day in tour mode, with a few hills, uses about 120 Wh. A 500 Wh battery lasts about three and a half days: charge it every two or three days and you’ll never cut it close.
A 56-mile (90 km) tour on rolling terrain. With 625 Wh, you make it in tour mode with margin (about 69 miles estimated). In sport you wouldn’t (54 miles). Use eco on the flats and save the higher modes for the hills.
A 31-mile (50 km) e-MTB ride with 3,940 ft (1,200 m) of climbing, on knobby tires. With 750 Wh in tour mode, about 54 miles (86 km) of range: enough. With 500 Wh and turbo on every climb, about 25 miles (40 km): you’d run out of battery before the end.
Run your own numbers with the e-bike range calculator: enter your battery, weight, terrain and temperature and it gives you the miles in each mode.
How to get more range from your battery
- Use the lowest mode that keeps you comfortable. Switching from turbo to tour on the flats gives 36% more range (from 53 to 72 miles with 500 Wh).
- Keep your cadence up (70-90 rpm). Mid-drive motors work best there and use less than when you grind a big gear (how they compare with hub motors is in mid-drive vs. hub motor).
- Anticipate stops and start off in an easy gear.
- Keep your tires properly inflated and your chain clean and lubed (see how to clean and lube your chain).
- Ride a little slower on the flat. Dropping from 15.5 to 12 mph takes you from about 56 to 72 miles with 500 Wh in tour mode.
- Take care of the battery. A well-treated battery loses capacity more slowly; the details are in how to take care of your e-bike battery.
Common mistakes
- Believing the manufacturer’s maximum range. Catalog range figures are usually measured in ideal conditions: flat ground, eco mode, no wind and around 68 °F (20 °C).
- Comparing batteries by Ah. A 14 Ah battery at 36 V (504 Wh) doesn’t hold the same energy as a 14 Ah battery at 48 V (672 Wh). Always compare Wh.
- Planning a ride right at the limit. Leave a 15-20% margin: the wind shifts, and nobody wants to climb the last hill on a 55 lb e-bike with no assist.
- Forgetting the cold. The same ride you did in September can leave you stranded in January.
- Thinking descents recharge the battery. Mid-drive e-bikes don’t recover energy when braking.
Frequently asked questions
What drains an e-bike battery more, assist level or hills?
Both matter a lot, but assist level more. With 500 Wh on rolling terrain, going from eco to turbo takes you from 86 to 38 miles (139 to 61 km); in tour mode, going from flat to mountains takes you from 72 to 39 miles. Mountains and turbo together drop to 27 miles (43 km).
How much battery does 3,000 feet of climbing use?
On a 25-mile (40 km) ride with 3,280 ft (1,000 m) of climbing, in tour mode, about 280 Wh with commuter tires and about 310 Wh with knobby mountain tires: more than half of a 500 Wh battery. You get nothing back on the descent.
Why does my e-bike get less range in winter?
Because lithium batteries deliver less energy when cold. With 500 Wh on rolling terrain in tour mode, you go from 55 miles at 64 °F (18 °C) to 45 miles at 32 °F (0 °C) and 36 miles at 14 °F (−10 °C). Bosch recommends keeping the battery indoors on cold days and installing it right before you ride.
Is a bigger e-bike battery worth it?
For long or mountain rides, yes: going from 500 to 750 Wh gives you 50% more range (from 55 to 83 miles on rolling terrain in tour mode). For city trips of 6-12 miles a day, 400-500 Wh is plenty and weighs less.
Does riding faster drain an e-bike battery?
Yes: air resistance grows with the square of speed. With 625 Wh on flat ground in tour mode, riding at 11 mph (18 km/h) gives about 99 miles (160 km) of range and at 15.5 mph (25 km/h), about 70 miles (113 km). On a Class 3 bike that assists up to 28 mph, the drop is much steeper.