An experimental four-bedroom house 20 miles north of Washington, D.C., was a net-producer of electricity halfway through its first year of operation, producing a surplus of 328 kilowatt hours of power.

Built on the campus of the National Institute of Standards and Technology (NIST), the house is occupied not by people but by an electronic version of a family that researchers have nicknamed the “Nisters.” Equipment inside the building mimics the habits of a family of four (two working parents and children 8 and 14 years old), including bathing, cooking, doing the laundry, and playing video games.

The 2,700-square-foot house — described in a blog by Allison Bailes and a GBA news article by Richard Defendorf — is in reality a laboratory designed to test materials and systems that advance energy efficiency. It’s equipped with photovoltaic panels, a solar hot-water system, and hundreds of sensors that monitor energy consumption.

From July, when the first net-zero energy test year began, through October, the house was generating a surplus of electricity every month, the NIST website reported. In November and December, production had dipped into the red but at the six-month mark, it remained on the plus side of the ledger.

NIST doesn’t post real-time energy data, but you can read monthly summaries of energy use, usually about 60 days after the month has ended, at the NIST web page devoted to the project.