As former House Speaker Tip O'Neill was known to say, “All politics is local.” Such has been the case for former Vice President Al Gore, who, in April, got the green light to install 33 photovoltaic panels on the roof of his Nashville, Tenn., home following lengthy city council negotiations that culminated in a zoning change to allow solar.

Unfortunately, the approvals didn't come fast enough to preempt some bad press for the former-veep-turned-environmentalist. Around the time Gore was accepting an Oscar for his groundbreaking documentary on climate change, critics with the libertarian Tennessee Center for Policy Research came forth with the revelation that, according to local utility records, the Gores' 10,000-square-foot mansion gobbled up close to 221,000 kilowatt-hours of electricity in 2006—more than 20 times the 10,656 kilowatt-hours required to power the average American home per annum.

The Gore camp was quick to rebut by pointing out their conscientious, ongoing purchase of carbon offset credits, along with the impending solar renovations to their 70-year-old abode and the installation of high-performance thermostats and windows.

The house might have proved even more energy efficient were it not for a zoning stipulation that a home's solar roof panels lie flat (not angled) for aesthetic purposes—a requirement that will decrease the system's photovoltaic efficiency by about 12 percent. But the larger question remains: How efficient can a 10,000-square-foot residence for two empty-nesters be?