Some time ago I switched my electricity supplier to Good Energy, thinking that it would mean that my electricity use wouldn't be contributing to CO2 emmissions. On Saturday my friend Bill came up with an argument that made me rethink green electricity.

In the UK, thanks to privatization, customers can choose their electricity supplier. This means it's possible to switch to green electricity. The question is; what difference does it make if I do?

Under the Renewables Obligation every electricity supplier in the UK has to buy a certain percentage of renewable electricity (about 7% at the moment I think). Electricity that qualifies as renewable receives Renewable Obligation Certificates (ROCs). ROCs can be traded separately from the electricity.

Bill's point was that if you change to a green tariff, it won't cause any more renewable energy to be produced because the electricity demand of people on a green tariff is under 7% of total electricity demand, which is no more than suppliers have to do already by law!

I thought hard about this and I think he is only right if your green supplier only holds on to the minimum number of ROCS.

Another way of putting it is that the greenness of electricity is soley determined by whether you retire the ROCs for it, rather than selling them. My electricity supplier, Good Energy, retire some of their ROCs, so I think that my electricity is a bit greener than the 7% national average. I'd like Good Energy to retire all their ROCs. It would cost more but I'd prefer to pay the extra and not contribute to global warming.

I can think of two other considerations for how green electricity is. People say to me, 'At peak times, wind turbines can't generate enough electricity and you have to use electricity from fossil fuel sources. Okay, your supplier does offset this with giving other people renewable energy at off-peak times, but it's still not entirely green'. I think this is a minor point compared to the ROCs one, but still I think it is valid. I'd like Good Energy to not do offsetting if possible.

The other consideration is non-energy costs. I've been told that only about 60% of an electricity bill goes on the actual electricity, the rest goes on wires, transformers, administration, meter reading etc. What are Good Energy doing to reduce the carbon footprint of this aspect? Perhaps they could have meters that communicate wirelessly, rather than have a person drive around in a van?

I conclude that I was wrong to think that electricity from Good Energy would be completely free from carbon emmissions. However, I was right to switch to them because the associated emmissions are significantly lower than those from a brown electricity supplier. Also, if you try a thought experiment where all electricity is supplied by Good Energy, the UK's electricity would indeed be entirely renewable!