On our website we state
“The specifications advertised on our website are those supplied by the bike manufacturers. Please note that the range of electric vehicles is dependent on a number of factors including body weight, terrain, wind speed and tyre pressures and the maximum ranges quoted can by no means be guaranteed. In truth, the only way to be sure that a bike will accomplish a particular journey is to try it.”
Furthermore the power gauges are not an exact guide to the remaining range as they will vary considerably according to the load from the motor as you have noticed. The key to it all is to ensure you never have to push the bike home and, for that reason, we recommend charging the battery after each use so you always start with a full charge. I generally use my bikes for relatively short journeys and in practice I will do a number of these journeys without charging in between however whenever the power gauge suggests anything other than a full battery I get it back on charge immediately!!!