DAYLIGHT SAVING TIME ENDS at 2 a.m. Sunday, November 6, so mark your calendars and be ready to set your clocks back an hour.. Daylight Saving Time can be frustrating, but the practice does have a positive impact on energy consumption in the United States.

According to the U.S. Department of Energy, a 2008 study found the combined daylight saving – about four weeks’ worth – saved about 0.5 percent in total electricity usage every day. All those small savings add up to about 1.3 billion kilowatt-hours nationwide. That’s the same amount of power that more than 100,000 households use in an average year.

Generally, according to the DOE, those energy savings occurred during a three- to five-hour timeframe in the evenings—a time when most of us are relying on our home’s light bulbs for illumination.

How much power are those bulbs really using, and how much do you save by turning them off when you leave a room? The basic calculation beings with the watt rating of the bulb. Let’s say it’s 40 watts. In one hour, that light bulb will use 0.04 kWh of electricity. Multiply that by your electric rate per kilowatt-hour and you’ll see how much every hour that illuminated bulb costs you.

The simple answer stays the same: leave the light on and you’ll be paying for the electricity it uses, whether you’re enjoying the benefit or not. Turn it off, and those kilowatt-hours you save will, over time, add up.

Consider adding timers or using smart appliances to turn off the lights and save power when you forget. Bear in mind: if you haven’t made the switch from traditional incandescent bulbs to LEDs, you’re letting power go to waste. About 90 percent of the energy used by incandescent bulbs is shed as heat. LEDs remain the most efficient option, and you can turn them off and on as much as you like without any impact on the lifespan of the bulb. Also, be sure to turn the light off when you leave the room.