Homeowners generally gauge energy usage from their bills each month, but the real-time feedback system in Kaplan Thompson Architects’ BrightBuilt Barn acts as “an update on the mood ring,” said Phil Kaplan, company designer.

According to the New York Times, the prefabricated home is heated by a solar-powered energy system and retains warmth with its heavily insulated walls. Inside, a device detects energy usage and transmits the information to LEDs attached to the building’s exterior. When the home is creating more energy than it is using, the lights turn green; yellow is somewhere in between, and red means residents are using too many appliances and need to reduce the heat.

Kaplan is developing a BrightBuilt Barn prototype that sells for less than $200,000.