Pointless and confusing
I'm with Cambridge professor McKay on this one. (http://www.withouthotair.com)
He made a very serious attempt at quantifying what it will take to be sustainable.
My best quote: "if everyone does a little, then all we can achieve is a little" (such a no brainer mathematically it makes you wonder why people didn't see through that 'every little helps' slogan).
At the end of the day if we want to really save energy our best bets are insulating our homes and assisting our boilers with solar panels or underground heat exchangers.