Does a laptop recharger waste electricity when the laptop is not connected?

Solution 1:

Yes. Generally anything with a transformer in it will draw at least some power when plugged in. See here for more details on the types of devices that will typically use power even when off. The only thing that will keep a device from drawing standby power is if you actually break the circuit that the device is plugged into.

Solution 2:

Yes, not a whole lot but over time it does add up. It can also wear out the transformer sooner.

See http://electronics.howstuffworks.com/everyday-tech/plug-in-transformer.htm for more info.

Solution 3:

I just did a test with my P3 watt meter. One old DELL adapter (10+ years, for Latitude P3 650) uses 1.3W while the laptop is not connected. However, a recent HP adapter (2+ years) uses 0 W (at least from P3 watt meter reading).