EfficienCity is a virtual town, but pioneering, real world communities around the UK are using similar systems. As a result, they're enjoying lower greenhouse gas emissions, a more secure energy supply, cheaper electricity and heating bills and a whole new attitude towards energy.

What is decentralised energy? Well, it's pretty much the opposite of our present, outrageously inefficient energy system, which was designed to meet the needs of a society that hadn't even heard of climate change. This centralised system is a shambles - in fact, it would be impossible to invent a less efficient way of generating energy.

It's a little bit like putting radiators on the outside of your house instead of inside it; we're burning one lot of fossil fuels for electricity, and another lot for heat, but waste heat is a by-product of electricity generation. Can't we just burn one lot of fuel to generate electricity, and capture the 'waste' heat at the same time?