When DVRs sleep, do they dream about energy-saving chips?

Ranked by the National Resources Defense Council (NRDC) as a domestic electrical power hog on gluttonous par with the refrigerator, the HD DVR is about to be put to sleep.

Don’t worry. It’ll wake up in time to record Jersey Shore. But the question is, how deep a sleep will your DVR go into and how much power will it save?

As profiled earlier this week by consumer-electronics lifestyle pub Electronic House, a wave of energy-efficient innovation has already started to over-run a home device that suddenly — with the wide-scale adoption of high-definition programming and digital video recording — has become a huge power consumer.

Also read: How green are the devices that stream Netflix & Hulu?

The problem has gotten pretty bad. According to an NRDC study released last year, the typical cable-, satellite- or telco-leased HD DVR uses 446 kilowatt hours of power each year — more than an Energy Star rated 21-cubic-foot refrigerator, which uses 415 kWh per year.

Sleep’s the thing

A big part of the problem is that these devices are on 24/7. Even when I power down my DirecTV two-tuner HD DVR, for example, I’m for the most part only turning off the elegant blue-lit display. All of the box’s critical functions remain on.

CableLabs, the cable-industry research consortium, has pledged that by September, the top six cable operators in the U.S. — together representing 85 percent of cable subscriptions — will start leasing their customers set-tops that go into “light sleep” mode.

Defined by the Environmental Protection Agency’s Energy Star specifications, light sleep allows essential activities within a set-top to continue while other power-using tasks, such as channel tuning and video display, are discontinued. Unless it’s recording something, the box doesn’t need to be doing these things.

CableLabs research shows that this feature can cut power consumption by as much as 20 percent.

But chips currently available for set-top boxes enable a much more restful, power-saving night of slumber.

Chip sets manufactured by Broadcom, (s BRCM) for example, enable a sleep level called “deep standby,” whereby the CPU and almost all other box functions are shut down. The device uses less than a watt of power in this mode, company officials say, and it can restart the basic task of decoding video in about four seconds.

As a Broadcom spokeswoman told us Thursday, the feature is available to the many multi-channel operators the company sells chips to. But for pay TV operators pimping out houses with whole-home-connected always-on systems, four seconds may be too slow. When it’s not inviting litigation from the broadcast networks by deleting their commercials, for example, Dish Network’s (s DISH) new Hopper DVR records every prime time show from the Big Four channels. When does it have time to enter deep sleep?

Citing EPA data, Electronic House pointed out that as of April, only two of the 57 pay TV set-tops that qualify for the Energy Star 3.0 specification enable a deep sleep mode. (Currently, Energy Star specs don’t mandate deep sleep, although the EPA is considering it for revised specifications that will debut next year.)

Beyond sleep

Fortunately, chipmakers have integrated a number of other power-saving features recently that don’t temporarily shut down the box. For example, multi-tuner devices used to require multiple chips. But new products from Broadcom and Intel (s INTC) have consolidated this process onto a single chip, saving the need for wattage in the process.

Meanwhile, so-called “thin clients” have already been widely adopted. Dispersed in areas of the house beyond the living room, these devices connect to the main set-top via Ethernet cable or coax, providing video programming access at a fraction of the power-use of a full-service DVR.