CHIBA, Japan -- For years, TV makers competed over price and screen size. Now they're beating each other up over who is the most green.

The environmental friendliness of TVs is the new battleground for set manufacturers, at least from my interviews at Ceatec, a technology trade show taking place in the Tokyo suburb this week. Sony, for instance, has a 42-inch LCD TV from 2005 on display that consumes 131 watts while showing programs. Next to it is a 2008 set of the same size consuming 57 watts to show the same program.

Sharp also has two experimental TVs that run on solar power. One, a prototype 26-inch LCD TV, consumes only 40 watts of power, less power than a conventional light...

CHIBA, Japan -- Startups that make green homes be warned: Panasonic is coming. It will take a few years, but it’s coming.

The Japanese electronics giant has assembled a strategic plan to start making modular homes in about three to five years that will combine green construction along with sophisticated electronics to curb energy consumption, according to executives during a roundtable discussion at Ceatec, a large technology trade show taking place near Tokyo this week.

In a Panasonic demo at the show, sensors embedded in the ceiling adjust the air conditioner and lights depending on whether or not people are present. The sensor system (based around a technology called Beam...