LEDs come on instantly and convert nearly 100% of the power they consume into light.

According to the US Dept. of Energy, in 2012 about 49 million LEDs were installed in the US, saving about $675 million in annual energy costs. Switching entirely to LED lights over the next two decades could save the US $250 billion in energy costs, reduce electricity consumption for lighting by nearly 50 percent and avoid 1,800 million metric tons of carbon emissions.