I'll admit it: I'm unrelenting when it comes to turning off lights. Growing up, my dad constantly reminded us to flick off the switches the second we left a room and nowadays I play that role, with my boyfriend at the receiving end. He's all for being smart when it comes to consuming electricity—he grew up in the San Francisco Bay Area and went to school in Boulder after all—but we don't always see eye-to-eye on the lights-on-or-off issue. While I insist on flipping the switches, he often comes back with a comment about the amount of energy used around the clock by the fridge.

When we received Belkin's Conserve Insight energy-use monitor at the office, it was game on. The device is a simple tool designed to help you "save energy through discovery." In layman's terms, you plug it into a wall, plug a electricity-dependent item into that plug, and read off the number of watts it's pulling, carbon dioxide it's producing, and money it's costing you to keep it running. This was my chance to prove that...well, that I was right about incessantly turning off the light.

Running around the apartment, however, proved far more fun than naming a winner and loser. On a recent Saturday, we methodically walked room to room, taking turns testing each electronic or appliance in its on and, if possible, off and standby modes and then recording the data.

In the end, we tested 27 items in our apartment that are always or often plugged in. In the kitchen: microwave, radio, KitchenAid mixer (plugged in only when in use), toaster, and refrigerator. In the dining and living rooms: one power strip, three lamps, one computer, one printer, the TV, a DVD player, the cable box, the modem, the router, and a stereo. In the bathroom: two electric toothbrushes and a hairdryer (plugged in only when in use). In the bedroom: a paper shredder, two reading lights, one lamp, a digital clock, and two phone chargers.

A few things surprised us. First was how much electricity is required to power the microwave, toaster, and hair dryer: each drawing up to 1,660 watts when on (which shows it's no wonder hair dryers are so good at tripping circuit breakers). Second was how little overall energy we use when not at home. Third was how much energy light bulbs pull. Finally, our fourth surprise—to my relief—was that far fewer items than I expected draw vampire energy. The KitchenAid mixer, toaster, power strip, printer, TV, lamp, stereo, phone chargers, reading lights, paper shredder, and bedroom lamp all pull zero watts when plugged in but turned off. The microwave, radio, power strip, DVD player, toothbrushes, phone chargers (when the phones are plugged in and fully charged), and digital clock each use less than two watts when plugged in but not on.

To further explain my surprise at the small amount of energy that we use when not at home and the comparatively large amount of electricity required for a lamp, let me go into further detail. When we're not home, the only items that are actively on are the fridge, power strip, the cable box, the modem, the router, and the digital clock. Those, plus the items on standby or plugged in but off, draw only 82.5 watts. (We assigned the fridge 30 watts when we're not opening and closing it since it ranged from 0 to 15 watts when maintaining its temperature to 866 watts the few moments after we had the door open and were rifling for food). With a baseline of 82.5 watts, every little action when we are home seems great. Turning on a 25-watt reading light suddenly increases our electricity use by more than 25 percent. (We use CFL and LED bulbs where we can, which only require about 6-8 watts each, but like many people, we have a number of fixtures designed for certain bulbs without CFL or LED alternatives.)

In addition to taking survey of our electricity consumption, the Conserve Insight was also able to tell us the pounds of carbon dioxide our energy use was releasing into the air (887 pounds per year for our baseline consumption) and the cost of running each appliance and device ($84 per year for our baseline consumption). The energy-use monitor is preset with U.S. averages to calculate pounds carbon dioxide released and dollars spent but can easily be customized to rates more accurate to your region.

Overall, the experience was quite enlightening. There are things we could do to reduce our load (unplug those toothbrushes when fully charged, unplug the radio when we're not using it) but we were happily surprised to know we're doing a lot better than we expected. And, we agreed I won. When your baseline is pulling 82.5 watts, adding another 25 is significant—so turn off that light.