Energy efficiency used to mean keeping the thermostat below 68 degrees or putting on a sweater.

No longer.

A generation of study and technological advances have transformed the field — making huge economic and environmental savings possible.

In his State of the Union address on Tuesday, President Obama challenged the nation “to cut in half the energy wasted by our homes and businesses over the next 20 years.”

Is it even possible? And could the widespread use of energy efficient technologies stem the rising tide of climate change?

Energy and environmental experts Dick Henry and Douglas Foy offer their insights.