A basic wattmeter costing in the range of $40-$50 is all you really need. More expensive models add some convenient features such as memories and the ability to connect to a computer. The extra features are nice to have but not necessary.

Avoid wattmeters that require pressing a button to cycle between the measured parameters. That is, you can only view one parameter, such as voltage, at a time and must press a button to see other parameters. These meters are less useful than those that display the important parameters volts, amps, watts, and mAh all at the same time on one screen.

The majority of wattmeters are of the latter type, displaying all four parameters simultaneously, which is what you want.

- Jeff