Great product. Just picked up another one. Good price too.

Why would you need more than one?

To see how much energy the meter uses. Haven't you read these posts before?

I suppose you could leave one plugged in to a major appliance or device for a month or so to evaluate its total energy consumption over that time.

Or in my house its just another thing I'd put on the shelf for some "important" project to do later and then forget about.