A consumer group says many laptops it tested had battery lives around half those advertised by manufacturers. The difference may well come down to “real world” use vs generous lab testing conditions.

Which?, a UK group similar to the US’s Consumer Reports, gathered together data from its tests of 67 models over the past year. It says that in each test it runs through six cycles running from a full battery to the machine shutting down. Three of the cycles involve continuous web browsing and the other three are continuous video playback.

The results (pictured) were good news for Apple: across the three models tested, the average battery life was 10 hours 15 minutes, which actually exceeded the average advertised life of 10 hours. The other six brands all fell well short, with HP having the biggest average gap: five hours two minutes in practice against nine hours 48 minutes in the marketing. Some individual models lasted less than half the listed durations.

According to Which?, Dell made the point that real world performance will vary from user to user and likened it to variations in gas mileage achieved by different drivers in the same car. Of course, that doesn’t determine whether or not the set-up used by manufacturers for test is a fair representation of an “average” customer’s use of the machine.

[Image credit: Which?]