Set your TV to "home" mode.

When setting up your new TV, be sure to pick the “home” mode setting. This setting may cut your power use by up to 25 percent compared to other settings such as “vivid” or “retail” which are unnecessarily bright for most users.

For more information on finding the most energy efficient TV in the size that you wany, check out NRDC’s guide to energy efficient TVs on SimpleSteps.org.