We have smart phones, smart meters, smart fridges, smart washers, smart cars and more. We need a central hub to collect and report the Eco-footprint. That is where the Zigbee Alliance comes in.
A device (works with most homes) creates a central hub to pair with and communicate to these smart devices. That way if a fridge is using too much power, you can reconfigure when it gets defrosted, when it runs.