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(Reuters) – Perched on a hilltop outside Washington, the U.S. government’s net-zero energy laboratory looks a lot like the luxury houses nearby, with two significant differences: it will make as much energy as it uses, and only sensors, not people, live in it.

Designed to fit in a typical residential neighborhood, the 4,000 square foot (372 square metre) net-zero lab on the suburban campus of the National Institute of Standards and Technology is so energy-efficient that over the course of a year it is expected to produce as much energy as it needs.

Its total energy consumption should be “net zero.”

To measure energy use, researchers at NIST have created a virtual family of four – two imaginary working parents, a 14-year-old and an 8-year-old – and scripted their every meal, move and shower. The energy use of this typical family will be monitored.

Sensors and computer programs will simulate virtual people entering the living area or moving from room to room, taking a bath, cooking a meal, turning on a computer, a television or a toaster. The appliances and plumbing do exist and are controlled from a command center of sorts, located in the detached garage.

Small devices will simulate the heat and humidity that actual humans produce in the two-story, four-bedroom structure.

“This family is very cooperative, they do exactly what we want them to do, every minute of the day,” Hunter Fanney, chief of NIST’s Building Environment Lab, said at the project’s official launch last week.

To gauge water use, the master bedroom’s shower is fitted with a scale. Step into the shower stall and onto the scale, and a weight read-out appears outside. When the lab is in use, the system will figure out by weight whether the virtual parents or children are taking a shower, and how much hot water they use.

The simulations assume that the 14-year-old will take the longest showers, Fanney said.

TESTING ENERGY-SIPPING TECHNOLOGY

Solar panels on the roof generate electricity and heat water. There are no roof gutters, partly as an aesthetic statement, but also because the lab-house is surrounded by a deep layer of gravel through which rainwater can percolate.

The garage is built across a breezeway from the main house so all the heat from the monitoring equipment doesn’t add to the lab’s energy load. There’s an electrical outlet for an electric car and a wheelchair lift that allows no-stair access to the main floor of the building.

This is not the only net-zero house in the United States, but it is the first created to look and feel like an amenity-filled suburban home, according to NIST. Most net-zero homes make it to net-zero by cutting down on size and amenities.

A house similar to the lab was built in Concord, Massachusetts, for about $600,000, exclusive of the cost of the land, said Betsy Pettit of Building Science Corporation.

A lower-cost not-quite-net-zero home was built for Habitat for Humanity for about $150,000, Pettit said, but that one was about 1,200 square feet (111 square metres), less than one-third the size of the NIST lab.

NIST’s lab cost $2.5 million, because it will do more than monitor energy use, and the monitoring equipment is costly; after the first year, it will be a test bed for new technology.

Funded by the American Recovery and Reinvestment Act of 2009, which made environmentally friendly construction a priority, almost every component of the structure was made in the United States.

The one exception was an air exchanger made in Canada. The project got a waiver to buy it when this item could not be found in the United States, a NIST spokeswoman said.

(Reporting By Deborah Zabarenko, Environment Correspondent; Editing by Fred Barbash and Todd Eastham)