Battery capacity is only part of the story
Battery capacity is normally expressed in watt-hours (Wh). A larger Wh figure generally provides more stored energy, but it does not guarantee a particular number of miles.
What changes real-world range?
Rider weight, hills, wind, temperature, tyre pressure, riding speed, assistance level, stop-start traffic and the bike's motor system can all change how quickly energy is used.
For commuting, it is more useful to think about your typical journey and build in a sensible margin than to rely on an optimistic maximum-range claim.
Range anxiety is often a planning problem
Know your normal route, charging opportunities and return journey. If the bike will be used for longer rides, compare battery capacity alongside the efficiency and characteristics of the motor system.
Battery safety belongs in the buying decision
GOV.UK advises users to buy complete e-cycles from reputable retailers, use genuine compatible chargers and batteries, and follow manufacturer charging instructions. The guidance also highlights warning signs including excessive heat, swelling, unusual noise, smell, charging problems and smoke.