If you’re wondering how much electricity certain appliances are using in your home, there is a simple way you can find out. Invest in a device called a Kill-a-Watt: a simple gadget that can determine your electricity usage. All you have to do is plug in the appliance/electronic item into the Kill-a-Watt and then plug the Kill-a-Watt into an electrical outlet. Let it sit like that for a week or two and the Kill-a-Watt will measure how much electricity the item uses.

Kill-a-Watts cost between $20 and $50 depending upon the model, but the tool should pay for itself if you’re serious about energy savings.

Here’s what Northern Cheapskate had to say:

I used the Kill-a-Watt to find out what an energy sucker my 1980s chest freezer was. I estimated that the freezer was costing me about $10/month to run. I’ve since bought a new chest freezer that only costs me about $3 a month to run. I’m now looking to see what other appliances in our home are using too much energy.

What do you think? Is the Kill-a-Watt a smart investment?