What percentage of the UK’s electricity is generated by small power plants supported by Feed In Tariffs? I think the answer is about 0.6%. At current rates of growth, this will rise to about 1% by this time next year. Most power plants supported by Feed In Tariffs (FiTs) are small, often very small. Their output isn’t recorded in statistics of electricity generation. In fact most of the time the PV panels on your neighbour’s roof are reducing her electricity consumption rather than producing a flow of electricity into the power network. But knowing the rated power of installations claiming FiTs, and estimating how much yearly electricity each kilowatt produces, we can guess the total amount of power produced over the course of a year.
The March FiT statistics have just been published. The total capacity of all installations registered under the scheme is now about 1.8 gigawatts (slightly larger than one of the new nuclear power stations planned for Hinkley in Somerset). Most of this capacity is solar PV.
|Technology||Share of total FiT installation capacity|
The imbalance is even more pronounced if we look at the number of installations. Solar PV is 99% of all sites claiming FiT because these installations are typically much smaller than wind or other technologies. Over 1 household in a 100 now has solar panels on the roof but these are generally below 4 kilowatts in size. A new wind turbine claiming FiTs might be hundred times the potential power.
PV panels don’t work at night, and barely function on a cloudy December day. In fact, solar panels produce an average of about 10% of their rated capacity. So a 4 kilowatt array on a roof will, over the year, average about 400 watts. It’s more in Cornwall and less in Aberdeen but this is a roughly correct average.
We can use similar estimates for the other main feed-in technologies: wind, hydro and anaerobic digestion. My figures are in the table below
|Technology||Estimated output as percentage of rated capacity|
The smaller technologies have higher percentage outputs, meaning that they contribute more to the electricity generated under the FiT scheme.
Simple multiplication produces the following estimates of annual electricity output from the currently installed FiT plants.
|Technology||Electricity generation estimate (GWh)|
The total amount of electricity consumed in the UK in 2012 was about 317 GWh. (The amount generated was greater because of losses in distribution and in running the power stations themselves). Therefore the electricity generated under the FiT scheme was about 0.6% of all electricity used in homes, offices and businesses.
The amount of generating capacity inside the FiT scheme rose by 65% in the year to March 2013 and growth is fairly steady. Wind and AD grew much faster than the average, albeit from a small base. If the growth continues, all FiT installations in March 2014 will supply about 1% of UK electricity in the following year.
 Please tell me if you think these estimates are wrong