I bought a outlet power meter from Amazon — the kind where you plug-through the device to reach to the actual outlet — and the device measures energy usage. This particular one has the basics: power (kWh), current (A), AC voltage (V, presumably rms), and a couple oddities like power factor and energy cost that I don’t think are especially useful due to the lack of tuning options in most devices (power factor) and the complexity of power billing not taking into account all the parameters. For example: time of use, base costs, and surcharges complicate the billing. In any case, there’s a good chance you’ve seen this before.

I highly recommend trying this or borrowing such a meter from a friend to really bring home the reality of how much power various devices consume. For example, I learned that my phone (5W) laptop (18W) and desktop tower alone (70W) all use less energy than a box fan than I run all the time in our living room (74W)! Indeed, I was surprised how efficient electronics are and how comparatively expensive it is to move air. I was able to disable some devices that are rarely used, but this only saves a few watts compared to the 1000W used by the AC unit and most likely dominates our summer power bill.