An e-bike is the cheapest motorised way to get to work that most people will ever own. It's also easy to overpay for, because the spec sheet leads with the numbers that sell bikes rather than the ones that tell you how the bike will live with you. Here's how to read it.
The short version
- Compare batteries in watt-hours (Wh), not in claimed range.
- Work out your own range: watt-hours divided by roughly 10 Wh per km gives a sensible commuting estimate.
- Prefer a battery you can buy again in five years. Proprietary packs from small brands are the main long-term risk.
- Check your local power and speed limits before you buy. They differ more than you'd think.
- Hub motor or mid-drive is a real choice, not a quality ranking. Pick for your hills and your budget.
- Look for battery safety certification. In some cities it's now the law.
Why an e-bike for commuting
A bike is the most space-efficient way through a congested city, and the motor removes the two things that stop most people cycling to work: hills and turning up sweaty. It also stretches a comfortable commute from about 8 km (5 miles) to 15–20 km (9–12 miles) for an ordinary rider.
The running costs are tiny, and this is where the numbers get fun. Bosch, the biggest e-bike motor maker, quotes an average of about 7 Wh per km from its own range testing. Call it 10 Wh/km for a heavier rider, a hilly route or a lot of stop-start. That's 1 kWh, one unit on your power bill, every 100 km (62 miles).
At 30 cents per kWh, a 20 km (12 mile) round trip costs 6 cents in electricity. Swap in your own tariff: it's the same arithmetic in any currency. On a solar-powered day it's close to nothing.
The other savings are parking, fuel and, in some cities, congestion charges, none of which apply to a bike. Some employers will also pay you to give up a parking space; it's worth asking.
How the assistance works
Almost every e-bike sold for commuting is pedal-assist: the motor helps only while you pedal. There are two ways the bike decides how much help to give.
- Cadence sensors detect that the cranks are turning, usually with a ring of magnets, and add a set amount of power. They're cheap and simple, but the help can feel like an on/off switch.
- Torque sensors measure how hard you're pushing on the pedals and add power in proportion. The ride feels more natural, like having stronger legs. They're now common on mid-range bikes, and if you can test ride both, most people prefer torque.
Some bikes also have a throttle, which powers the bike without pedalling. Whether that's legal depends on where you live (see below).
Hub motor or mid-drive?
Neither is "best". They suit different riders.
Hub motors
A hub motor sits in the centre of a wheel, usually the rear. Most are geared hubs: small, light, and able to freewheel, so the bike rolls easily with the motor off. Direct-drive hubs have no gears inside, are larger and heavier, and are now mostly found on cheap or heavy-duty bikes.
The case for a hub motor:
- It's cheaper, because the frame doesn't need a special bottom bracket. For the same money you often get better brakes, wheels and frame.
- It doesn't load the chain, so drivetrain wear is close to a normal bike's.
- The feel is a gentle push from behind. Some people love it; some find it less natural.
The catch is the wheel. A motor wheel is heavier, and fixing a flat on it takes more steps (unplug the cable, line up the axle carefully). Ask the shop to show you a wheel removal before you leave. Our puncture guide covers the rest.
Mid-drive motors
A mid-drive motor sits at the cranks and drives through the bike's chain and gears. That means the motor can use your low gears on hills, which makes mid-drives the better climbers for the same power rating. They also keep the weight low and central, so the bike handles like a bike.
The trade-off is wear. All that extra torque goes through the chain, cassette and chainring, so they wear faster than on an unassisted bike. Budget for a new chain every year or two of daily commuting, and replace it before it stretches, or it will take the cogs with it.
If you're buying second-hand, look closely at the teeth on the chainring and rear cogs. Hooked, "shark fin" teeth mean the whole drivetrain is due, and that the bike wasn't looked after.
Our take: for a flat-to-rolling commute, a good hub-motor bike is the better value. For steep hills or heavy loads (kids, shopping, a cargo bike), a mid-drive earns its extra cost.
Range: ignore the brochure, do the sum
Claimed ranges are measured in ideal conditions with the lowest assist setting, and they vary wildly between brands. Hills, headwinds, rider weight, cold weather, tyre pressure and how much you lean on the motor all change the real figure.
A better approach is to compare battery size and estimate range yourself:
range (km) ≈ battery watt-hours ÷ 10
So a 500 Wh battery gives about 50 km (31 miles) of mixed riding, more if you pedal hard on a low setting, less in winter or in turbo mode. Bosch publishes an online range assistant that lets you plug in your own route, weight and conditions. It's worth five minutes before you choose a battery size.
Comparing battery capacity
Spec sheets don't always quote watt-hours. Some give volts and amp-hours instead, often whichever number looks biggest. Convert everything to watt-hours:
volts × amp-hours = watt-hours
- 36 V × 14 Ah = 504 Wh
- 48 V × 10 Ah = 480 Wh
Those two batteries are near enough the same size, even though one looks "bigger" on amp-hours and the other on volts. Work it backwards if you need to: 500 Wh at 36 V is about 14 Ah.
For most commutes, 400–625 Wh is plenty. A bigger battery adds weight and cost you'll carry every day, so buy for your longest regular ride plus a margin, not for a once-a-year adventure.
Batteries: the part that wears out
The battery is the most expensive part of an e-bike to replace, and it will need replacing eventually. Choose with that day in mind.
- Buy into a system with a future. Batteries from the big drive-system makers (Bosch, Shimano, Yamaha and similar) are widely stocked and supported for years. A sleek pack custom-made for one model from a small brand may be unobtainable in five years, which can turn a good bike into scrap.
- Ask about the cells. Packs built from cells by established makers (Panasonic, Samsung, LG, Molicel and others) are a good sign. A good shop can tell you.
- Look for certification. Cheap, uncertified lithium-ion batteries and chargers are behind a string of serious house fires. New York City has required e-bikes sold there to be certified to UL 2849 (the whole electrical system), with batteries to UL 2271, since 2023. In Europe, look for EN 15194 compliance on the bike. Use the charger that came with the battery.
- Avoid lead-acid and NiMH. They're heavy and obsolete; any bike using them is very old or very cheap.
How long does a battery last?
Expect several hundred to around a thousand full charge cycles before capacity drops noticeably, which for most commuters is somewhere between three and eight years. A "cycle" means a full battery's worth of charging, so ten top-ups of 10% count as one cycle. Bosch's standard battery warranty is shorter than that, so read the terms rather than the marketing.
Battery care that actually helps
- Heat and full charge are the enemies. Lithium-ion cells age fastest when they're hot and full at the same time. Don't leave the bike baking in the sun, and don't leave the battery on the charger all weekend.
- For daily riding, charging to about 80–90% is kinder to the battery than always filling up. Many bikes and apps now let you set a charge limit.
- For storage over a month or more, leave the battery at about 30–60% (two or three bars on most indicators), somewhere cool and dry. Bike makers using Bosch systems give the same advice.
- Never store it flat. A battery left empty for months can drop below the point where it can be recharged safely.
- Charge indoors when it's freezing, and let a cold battery warm to room temperature first.
Partial top-ups are fine. There's no "memory effect" with lithium-ion, so charging at work is a good habit if your commute is long.
How powerful should the motor be?
This is where your local rules matter more than your preferences. Power limits decide whether your e-bike is legally a bicycle or a moped that needs registration, insurance and a licence.
- European Union and United Kingdom: 250 W continuous rated power, with assistance cutting out at 25 km/h (15.5 mph). The UK no longer allows throttles beyond a walk-assist mode on bikes sold as standard e-bikes.
- Australia: 250 W with assistance cutting out at 25 km/h is the national standard. New South Wales has allowed some higher-powered bikes, but it is moving to the same 250 W standard; check the current rules in your state.
- New Zealand: up to 300 W, and the bike must be mainly propelled by pedalling. Anything more powerful is treated as a moped.
- United States: no single national rule. Most states use a three-class system: Class 1 is pedal-assist to 32 km/h (20 mph), Class 2 adds a throttle to the same speed, and Class 3 is pedal-assist to 45 km/h (28 mph). The federal consumer-product definition caps motors at 750 W.
Don't over-read the watt figure. "Rated" or "nominal" power is the continuous output, and most motors briefly deliver much more when you need it. A 250 W mid-drive with good torque will climb steep hills perfectly well. What you feel as "power" is mostly torque, quoted in newton-metres (Nm): around 50 Nm suits flat commutes, 75–90 Nm tackles serious hills and heavy loads.
Be wary of claims that one 250 W motor "outperforms" another by a few per cent. Reliability, service support and the warranty matter far more than small efficiency claims.
Is regenerative braking worth it?
A few bikes, mostly with direct-drive hub motors, recover some energy when you brake. In practice the gain is small, typically a few per cent of range. A bike isn't heavy enough, or fast enough, to store much energy, and you lose some in converting it. It does save a little wear on the brake pads.
Our take: nice if the bike you want has it, but not a reason to choose one bike over another. If you want more range, buy more battery.
What to check before you hand over money
- Watt-hours, and whether that battery will still be sold in five years
- Battery and charger safety certification (UL 2849/2271, EN 15194 or your local equivalent)
- Motor brand, torque in Nm, and who services it locally
- Legal class in your area, so you can ride it on cycle paths
- Brakes: hydraulic discs are worth having on a heavier bike
- Mudguards, lights and a rack, if it's a commuter, because adding them later costs more
- A proper test ride, ideally on a hill
This article is a 2026 rewrite by Cole of Mark's 2019 original, with the numbers and rules updated.