E-bikes: how to choose, range, rules and charging

1. Motor: hub vs mid-drive

• Rear hub motor: sits in the back wheel. It's simple, quiet and low-maintenance, and is the most common type on commuter, folding and fat-tyre bikes. It's weaker on long steep climbs.
• Front hub motor: cheap and easy to fit, but traction can slip on loose or wet ground.
• Mid-drive motor: drives the cranks, so it works through the gears. It climbs better and feels more natural, but costs more and wears the chain faster.
• Torque sensor vs cadence sensor: a torque sensor gives assist in proportion to how hard you pedal. A cadence sensor switches on once the cranks turn. Torque sensors feel smoother and usually give more range.

2. Battery size (Wh) and range

Battery capacity in watt-hours = volts × amp-hours (for example, 48 V × 14 Ah = 672 Wh). Most riders use roughly 10 to 25 Wh per km on assist. Hills, headwind, rider and cargo weight, cold weather, knobbly or fat tyres and throttle-only riding push it towards the high end.

Estimates: range = Wh ÷ Wh per km. 1 km ≈ 0.62 miles.

3. Charging time, weight and frame style

• Charging time ≈ battery Wh ÷ (charger volts × amps). A 2 A charger on a 48 V pack delivers about 100 W, so a 672 Wh battery takes roughly 6 to 7 hours from empty. A 4 A charger roughly halves that.
• Weight: many e-bikes weigh 20 to 35 kg. If you carry the bike up stairs or onto a train, check the weight and whether the battery comes off.
• Folding: compact for flats, boats and campervans, but smaller wheels and batteries. Commuter / city: mudguards, racks and lights, built for daily rides. Fat-tyre: grip on sand, snow and gravel, but heavier, and the tyres use more energy per km.

4. Power and speed rules by region

This is a summary of the official rules as checked on 4 Nov 2026. It's general information, not legal advice. Rules change and can vary by state, so always confirm with your local authority before you buy or ride.

• New Zealand: a power-assisted pedal cycle has one or more auxiliary motors with a combined maximum power output of no more than 300 W, and is designed to be mainly pedal-powered. It's treated as a cycle: no registration or licence is needed, but an approved cycle helmet is required. Above 300 W it's classed as a moped. Source: NZTA: Low-powered vehicles.
• Australia: an e-bike that meets the European standard EN 15194 (maximum 250 W, with the motor cutting off at 25 km/h, or whenever you stop pedalling above 6 km/h) is generally treated like a pushbike. Bikes outside these limits may count as road vehicles that need import approval. States and territories set the riding rules, and some differ (for example, NSW). Source: Department of Infrastructure: Importer's guide to electric bikes.
• United States: federally, a low-speed electric bicycle has fully operable pedals, a motor of less than 750 W, and a top speed on motor power alone of less than 20 mph. It's regulated by the CPSC as a consumer product. The three-class system comes from state law, not federal law: Class 1 is pedal assist to 20 mph, Class 2 is throttle to 20 mph, and Class 3 is pedal assist to 28 mph. Most states use it, but not all, and path access, age and helmet rules vary. Sources: CPSC: Bicycles FAQ and 15 U.S.C. § 2085. Check your state's transport department for the class rules.
• UK (Great Britain): an electrically assisted pedal cycle (EAPC) must have working pedals and a motor with a continuous rated power of no more than 250 W that can't propel the bike above 15.5 mph. Riders must be 14 or over. No licence, registration or insurance is needed, but you can't ride on pavements. "Twist and go" throttle bikes need vehicle approval. Source: GOV.UK: Riding an electric bike.
• European Union: Regulation (EU) No 168/2013, Article 2(2)(h), excludes from vehicle type-approval any pedal-assist cycle with a motor of no more than 250 W continuous rated power, where assistance cuts off when you stop pedalling and fades out before 25 km/h. These are pedelecs, and EN 15194 is their safety standard. Faster or throttle e-bikes are L-category vehicles (mopeds) under national rules. Source: EUR-Lex: Regulation (EU) No 168/2013.
• Elsewhere: check your national transport authority. Many countries follow the 250 W / 25 km/h pedelec model.

5. Charging from a power station or solar

An e-bike charger usually draws about 100 to 250 W from the wall, so almost any portable power station can run it. A 500 Wh battery uses roughly 550 to 650 Wh from the station once inverter and charger losses are added. Read more:

• Charging an e-bike or e-scooter battery from a portable station
• E-bike charging during a blackout: the real Wh maths
• How many solar panels do you need? and AC vs solar charging speed
• Runtime calculator and What size power station?
• Mobility scooters and powerchairs
• Related: E-motorbikes · E-scooters · Home chargers for e-bikes, scooters and EVs

6. Battery care and safety

• Use the charger that came with the bike, or a certified replacement. Avoid cheap no-name chargers and batteries.
• Look for recognised safety certification, such as UL 2849 / UL 2271 in the US or EN 15194 in the EU, UK and Australia.
• Charge on a hard surface away from exits and anything flammable, and don't leave it charging unattended overnight.
• Stop using a battery that is swollen, damaged, very hot, or has been dropped hard or soaked. Recycle it properly.
• For storage, keep the battery around 40 to 70% charge somewhere cool and dry, and top it up every couple of months. Charge above about 0 °C.
• Have a professional fit any conversion kit. Modifying a bike to exceed local limits can make it illegal and uninsured.

Where to buy

ENGWE makes folding, commuter and fat-tyre e-bikes. Check the current models, specs and prices on their US store: E-bikes at ENGWE (US) (affiliate link). Outside the US, check your local dealers and confirm that the model meets your region's rules.