It's a dimmer switch that potentially could save megawatts of power.

HID Laboratories, a Silicon Valley startup armed with technology from Oak Ridge, Tennessee, has developed a digital ballast for controlling high intensity discharge (HID) lights, the bright bulbs that illuminate stadiums, streets, industrial and big box retailers. American River Ventures, out of the Sacramento region, recently invested in the firm.

Overall, HID's digital ballast can cut the power consumed by an HID light by 40 percent or more, said CEO Antonio Espinosa. Lighting consumes 22 percent of the power generated in the U.S. and the majority of the juice of that total goes to more than 100 million HID sockets in the country. Thus, if used universally, you're talking a big whack in electricity consumption.

VCs have been putting money into energy efficient lighting for the last several years, but mostly into companies that produce bulbs. Companies with complimentary technologies have received less attention, but some, such as Nuventix (air-cooler for LEDs) and Intematix (designer phosphors) have emerged.

To find out more, head over to Greentech Media's Green Light blog.