With heating season coming soon for many of us in the Northern hemisphere, it’s a good time to think about how we can cut our utility bills and reduce our environmental footprint. For some inspiration, we can turn to Sweden, where an amazing home called Villa Åkarp has managed to reduce residents’ energy bills to less than zero.

That’s right—even better than a zero-energy building, this home actually has a second identity as a power plant, producing more energy for the grid than it uses.

Villa Åkarp, completed in 2009 outside Malmo, Sweden with the help of technology from Rockwool International, uses many design elements drawn from the passive house movement. That means jealously guarding every bit of heat in the house: it’s hyper-insulated with more than 20 inches of insulation on the walls and roof, and krypton gas filling for the windows.

One bedroom ceiling even uses wax granulate in its drywall that melts when the temperature rises above 77 degrees Farenheit, drawing heat from the air. When it gets cold, the wax hardens, releasing the heat.

Every entrance and exit to the house, including the wastewater pipe, is calibrated to reduce heat loss. Hot water running down from the shower pre-warms the water coming in from outside, reducing the pressure on the hot water tank.

Heat and hot water come from thermal solar collectors and a pellet stove. Photovoltaic panels produce about 4,200 kWh of electricity per year, which, thanks to super-efficient appliances and LED lights, creates a surplus of 600 kWh.

Since Villa Åkarp went online, Rockwell says more houses like it have been built. They’re not for everyone yet, with a price tag $100,000 more than a similar home, but falling costs of solar panels may change that.

Meanwhile, if some of the high-tech bells and whistles involved in homes like this are out of reach for many of us, we can still look to some of its basic premises, like getting some better insulation, as winter approaches.

Featured image credit: Rockwool International