While it is not as "green" a pastime as, say, gardening, home theater enthusiasts can take some comfort that their passion doesn't make anywhere near the total environmental impact as "camping" with a large RV or dirt-bike racing. Nonetheless, our hobby does require power consumption; and, for those who are interested in saving a little money or trying to live a more environmentally aware lifestyle, you can make wiser choices as to what equipment you purchase and how you use it. Every bit helps.
In seeking to reduce home theater power consumption, there are a couple of general guidelines you can follow: 1. Turn off the most power-hungry devices in your system when you aren't using them; and 2. Use application-specific components instead of general-purpose ones to perform a home theater function.
Identifying Power-Hungry Devices
The most power-hungry components in a home system are its image-forming devices: flat-screen TVs or video projectors. In general, the larger a flat-screen TV or the more powerful (brighter) a projector, the more watts (the unit of electrical power) it will consume. The 32-inch 3D TV with fluorescent-bulb backlighting that I use when developing 3D test patterns consumes around 95 watts in operation and around 100 watts during startup (as the internal computer for the built-in WiFi, networking, and streaming-video-decoding functions is booted up). Once startup is done, its power consumption is pretty constant, due to the always-on nature of the fluorescent backlight. You can expect display technologies that have variable backlighting (LED TVs) or that generate light only in those pixels that need it (plasma and OLED screens) to have power consumption that varies with image content - the brighter the image, the more power consumed.
Aside from initial product selection (aided by Energy Star stickers, see below) or watching only film noir productions, there's only one thing you can do reduce the amount of power it takes to create the image in a home theater - reduce the overall screen brightness by turning down the brightness control or, for LCD screens, by turning down the backlight (for LCD sets, this is usually - and preferably - a different control than image brightness). For example, my 3D TV's power consumption drops from 95 watts to around 35 watts when I reduce the backlight control from full-on to all-the-way-down (which doesn't actually turn off the backlight). Of course, for such manipulations to be practical requires a darkened viewing environment and considerable recalibration of the basic picture parameters (brightness, contrast, tint, color, and gamma). But even with all the calibration tools in the world, a TV simply might not be capable of creating a good-looking image, much less an accurate one, with a too-low backlight setting. Try it and see.
Many gamers hook up their computers to their TVs to get, among other things, a more immersive large-screen gaming experience. But, all other things being equal (such as game graphics quality and the availability of equivalent game titles), a purpose-designed game system like a PlayStation or Xbox would likely require less power than a PC running the same game. This also holds for playing Blu-rays and DVDs on a PC compared with a standalone disc player and for the same engineering reason: good, purpose-designed hardware can be more energy efficient than the general-purpose computational facilities found in a computer, which have to work harder to produce the same video or audio signal.
For example, one of my PCs, a garden-variety dual-core model equipped with my test-signal-generating software, is hooked up to the aforementioned 3D TV. The PC alone consumes a constant 100 watts simply by virtue of being turned on and doing nothing more interesting than displaying a Windows 8.1 desktop. Playing a DVD with the PC boosts that figure: not only is the PC's CPU working harder, but lots of the calculations in decoding a DVD are being performed by PC's power-hungry graphics card. Changing the video-playback software also has an effect on power consumption; the VLC player is a power hog compared with WinDVD (10 versus five additional watts consumed, in this case). I attribute this to superior employment of the graphics card by WinDVD, but I could be mistaken. Contrast this performance to my garden-variety standalone Blu-ray player hooked to the same TV. It consumes 18 watts at idle and 21 watts when playing a DVD. So, if you want to save energy when playing a disc or streaming a network video, turn off the PC and use a purpose-designed disc player or the TV's built-in network functions. While you're at it, unless you need them, you should turn off your cable/satellite set-top boxes, which are startlingly power hungry (as can be observed in a power-meter reading and by how warm they get in operation). This would indicate to me that they contain circuits that are sub-optimally minimized for the functions they are required to perform...which should not be a surprise coming from a cable company.
Unless you have an unusual playback situation - a very large room, multiple extra surround speakers, rock-concert sound levels - the audio portions of a home theater system usually consume less power than the video components, even when playing loud music or soundtracks. With typical components, getting satisfying, moderately loud average sound levels takes around only one to 10 watts of power per channel! It's the very short, very loud peaks that might require hundreds of watts for clean and accurate reproduction. But, since the peaks are very short (a few milliseconds to a few hundred milliseconds), the total amount of average power is still close to one to 10 watts per channel.
Click over to Page 2 to find out what makes the Biggest Difference, the Energy Star label, and Testing Yourself . . .