TOKYO, Japan — TOYOTA is pairing its little known housing business with its expertise in green cars to sell computer systems that link homes, utilities and vehicles to reduce energy use.

The world’s biggest automaker said yesterday the launch of its home smart-grid system in Japan will coincide with its plug-in hybrid cars going on sale in early 2012.

Called the Toyota Smart Centre, it allows people to see on TV screens and mobile handsets how much electricity is being consumed by a household, how much a plug-in vehicle has charged, and how much electricity has been stored in the home.

It calculates the most efficient way of using energy, eliminating waste by shutting off gadgets when they aren’t being used and maximising the recharging benefits of hybrids, which recharge as they run. Utilities can also be used when rates are cheapest such as overnight to heat stored water.

The changes sound small, but the automaker says they can add up to significant savings when combined with computerised monitoring.

Toyota Motor Corp plans to sell several tens of thousands of plug-in hybrids a year, and hopes its smart-grid technology will also catch on, said Shigeki Tomoyama, managing officer, during a demonstration at a Toyota showroom.

Compared to a regular home and a gasoline-engine car, the smart grid and a plug-in will, in the best case scenario, reduce household energy consumption by 75 per cent, according to the automaker.

Other companies, including automaker Ford Motor Co and General Electric Co, as well as US states, are also working on smart grids.

The smart centre will work only with Toyota’s plug-in, likely making it no more than a niche product to start with. The maker of the Prius hybrid and Lexus luxury models did not give the system’s costs.

Tomoyama believes if plug-ins and electric vehicles become widespread, automakers will be called on to be environmentally responsible, as such vehicles will likely make up a third of a home’s energy use.

“Linking the home and the car will reduce global warming gases,” he told reporters. “That will become our social duty.”

Toyota has been testing its smart center in Rokkasho, northern Japan, since last month. It has not decided on any similar overseas projects. Toyota sold 5,300 homes in Japan last fiscal year.