It's there on the website to enable people to assess what changes they could make in order to reduce their carbon footprint by 10% in 2010 — that's the 10:10 campaign that Bob M. mentioned in his blog on 29 Nov.
The calculator is very vague in places, esp. on the 'diet' section: I mean, how am I supposed to work out if my diet is "lower" or "much lower" than "average" (more or less animal protein etc), given that the only descriptions are on the low and high ends of the scale? (If that's not clear, look at it and you'll see what I mean.) So you have to settle for being quite impressionistic about your answer on this scale. On the other hand you can be extremely accurate about rating your household running costs as long as you're able to get hold of a monthly breakdown of what you spend on gas and electricity, and your daily water consumption. The latter appears on your annual water bill, and for fuel costs my online fuel supplier provides the info I needed. Maybe it's on paper bills too?
I thought I was really clever when my footprint turned out to be much lower than the UK average, nearer that of China, apparently — smug, oh so smug! But I reckon this calculator is a pretty blunt instrument, so I'm not too sure how much I believe the results. Anyone found a better one?
One thing I did boggle at, though (if it's true): 40% of my footprint derives from the cost of living in this house: forget driving, flying, posh nosh, binge shopping, etc. — in my case it's the heating and lighting plus music, tv, Mac, fridge and so on that does the damage. And I am a dedicated switcher-off of radiators and lights etc. and had an efficient new boiler 16 months ago.
Two obvious points here. First, it's an old house and while I've done some things to make it less draughty etc, there's definitely a limit to how much the average DIYer like me can do to make an old house energy efficient and thus to lower its Co2 impact. Second, if several people live in one house as opposed to only one (me), overall running costs are higher but the cost per head almost halves with each extra person. So if even one other person lived here that would slash my 40% to nearer 20%. Communal living here I come . . . Now, how many lodgers can I squeeze in?