## July 29, 2008

### Carbon calculators

I was bored the other day, and thought I’d try out the government’s “Act on CO2” carbon calculator. I mostly put in just details about my own life, only adding in an extra car at 5,000 miles a year to see how much this would affect my carbon footprint. If you haven’t had a go at the calculator already, it asks you quite a few questions about your lifestyle – number of TV’s and how long they’re on, how many loads of washing you do a week and at what temperature etc. So I was expecting this to come out as pretty accurate.

I was surprised to find that my CO2 footprint (for my household, of 2) was 17.63 tonnes/year, compared to a national average of 10.2 tonnes/year (which I thought was per household by the way it’s presented, but I have a feeling is per person). Given that I live in a modern flat, which is very cheap to run, I was rather surprised by this figure (before anyone points the figure at my driving, my houshold came at just over 10 tonnes compared to transport of 7.4 tonnes). So I did some digging around…

Despite the claims that the calculator doesn’t double count, I’m pretty convinced it does. Having asked you what your bills are for gas and electricity (which surely is the sum of your carbon footprint, unless you add in water costs which it doesn’t ask you about), it then asks you lots of detailed questions about your appliances. I therefore dug around the web for 15 minutes, and calculated my own carbon footprint against the calculator’s. My results were:

2.9 tonnes Gas
0.7 tonnes Electricity
Total home: 3.6 tonnes

2.7 tonnes Petrol car
4.9 tonnes diesel car
Total transport: 7.6 tonnes

Total footprint: 11.2 tonnes
Total/person: 5.6 tonnes

This is based on my consuming 1500m3/yr gas, 3000kWh/yr electricity, 20,000 miles/yr of my diesel car (at 50MPG) and 5,000 miles/yr of a hypothetical fun petrol car (at 20MPG). Data used for calculation:

Natural gas 1.94kg/m3
Electricity 0.238kg/kWh
Petrol 10.68kg/UK gal
Diesel 12.22kg/UK gal

The table from the Carbon calculator, on the other hand, looked like this:

Total Footprint for Home 8.54
Heating & Hot Water 8.32
Lighting 0.22
Total Footprint for Appliances 1.67
Kitchen 0.62
Entertainment 0.42
Study 0.4
Other 0.23
Total Footprint for Travel 7.42
Vehicle 7.42
Flights 0
Total Carbon Footprint 17.63

The transport figures are in pretty good agreement, but the home section is pitiful. The heating and hot water (which is only gas) is about 3 times too high, and the electrical footprint is over twice as much as what I calculated.

The carbon calculator is a nice idea, but I think they need to do a bit more work a) Not double counting things b) Not disregarding what you give as your total household consumption and c) More clearly presenting per person and per household figures.

### One comment

1. #### alf

does it ask for your last bill or the whole year’s use? if it’s the whole year you are correct, but if it’s only the most recent one it needs to consider the variation in power usage through the year, in which case your usage habits, heating methods etc would be needed for an estimate. E.g. if your last one if for winter and it doesn’t calculate further then it will over-estimate the yearly carbon emissions.

18 Aug 2008, 22:42

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