Running it for about 5 hours every night adds up to 50 watt-hours per day. Over a 30-day month, that's about 1. . LED outdoor lights are highly energy-efficient, using far less electricity than traditional incandescent or halogen bulbs—usually just 3 to 10 watts. LEDs are designed to be energy-efficient. . The energy used by outdoor lights depends on a few things, like the type of lights, how many strands you use, and how long they're on each day. Each type uses a different amount of energy. 12 per kilowatt-hour, using halogen lights for 5 hours nightly costs 2. Now, let's switch to LED lights with. .