According to the British Wind Energy Association the UK has a total installed wind generation capacity of 1338MW and according to the International Small-Hydro Atlas the hydro (excluding pumped storage) capacity is 1349MW, a remarkably similar figure.

Generating 5,815GWh in a year from this 2687MW capacity would require an average availability factor of 25% which seems plausible.

Why was quarter 4 of 2005 10.4% lower than quarter 4 of 2004? Looking at the data on a quarterly basis shows that this drop wasn't unusual.

(Source: DTI Energy Trends 1.1)

Curiously the quarterly data states that quarter 4 of 2005 produced 0.11Mtoe (33.8% less than 2004) yet the Oct/Nov/Dec 2005 monthly data states 0.15 Mtoe (the 10.4% drop). Maybe the inconsistencies are due to this latest data being provisional but these points can be made:

• There are large annual and quarterly variations
• Q1 and Q4 generate two thirds more energy than Q2 and Q3
• Total contribution hasn't increased over the last seven years

One serious question remains unanswered though - why hasn't the primary electricity contribution from wind, hydro and solar PV increased at all over the last seven years?

I belive the answer lies in how hydro and wind are lumped together in the total energy statistics. Considering wind alone, the electrical output has shown 19% year on year growth between 1996 and 2004. This quadroupling was from a very low installed base and is lost in the noise when added to hydro. If and it's a pretty big if, this growth rate can continue wind could overtake hydro by 2009 and by 2020 be generating 30TWh per year, 8% of today's electricity production.