"The Heliotrope is Germany’s first energy positive house, producing more energy than its inhabitants consume."
An awesome idea here but maybe does not have widespread applicability, but..:
"The Heliotrope is a luxury solution: fully equipped, it would cost some two million dollars. Nevertheless, in 2000 the Schlierberg Solar Settlement in Freiburg installed Heliotrope technology in 50 homes and a commercial building called the “Sun Ship” creating an energy positive community. The settlement delivers a surplus of about 36 kilowatt hours per square meter.