HOW YOU CAN PLUG IN

* On Saturday, Oct. 16, the owners of more than 160 independently powered homes across the United States will throw a synchronized open house for people who want to see how ``off-the-grid'' systems work.

Real Goods, a California-based mail-order company that sells alternative-energy products, came up with the idea about a year ago. The company has equipped 20,000 homes with solar power and has seen revenues from its mail-order business increase from $26,000 in 1986 to $10 million by 1993.

The company, which has advertised the open house in its mail-order catalog and newsletter, says the response has been incredible. ``We're getting about 200 calls a day from people who want to know exactly where the homes are and where they can tour,'' says John Schaeffer, president of Real Goods.

To find the nearest open house to you, call Real Goods at 1-800-762-7325. The company will tell you the home or homes participating in your area. It will also send out a packet that includes a map and describes what type of energy - solar, wind, or hydro - the homes use. The open house takes place from 10 a.m. to 3 p.m.

``We tried as best as possible to get them interspersed throughout the country,'' Mr. Schaeffer says. New England, northern California, the Northwest, the Southwest, Colorado, Alaska, and Hawaii have the largest concentrations of off-the-grid homes.

The open house will include the world's first solar-powered subdivision, including a Burger King, city hall, library, and local community college. The 38-building neighborhood is located in Gardner, Mass., and was designed in 1984 by Steven Strong's architectural firm, Solar Design Associates, in Harvard, Mass. The Plymouth and near-Boston homes mentioned in the story at right are not participating in the open house.