For many years BM reports (Balancing Mechanism Reports) have published live generating statistics for UK electricity broken down by generating type. The data have always been fragmentary and difficult to access. Gridwatch have done all energy analysts a great favour and have been saving this data in an easy to access format. The CSV file I downloaded had data for the UK grid at 5 minute intervals from May 2011 to present. Below the fold are detailed charts of generating statistics broken down by nuclear, coal, gas and wind, from Jan to April 2013 – each chart contains about 9000 lines of data!
It happens quite often when I’m researching a post that I end up producing too many charts. So this post is really a chart-feast. My next post – hopefully Thursday, will take an even deeper look into UK electricity generation policy, the impact of wind on the grid and on UK trade balance. Too many charts would get in the way of the central messages of that post and so this is a dumping ground for all the charts.

Click on all charts to get a larger copy. Drag and drop to your desk top to keep a copy and then share if you want. But please read Blog rules before publishing elsewhere.

Figure 1

Figure 2

Figure 3

Figure 4

Figures 1 to 4 are stacked area charts of UK generation by source, January to April 2013. Many may recall that March was unseasonaly cold in the UK. If you don’t understand what these charts are showing then please read Electricity Supply and Demand for Beginners. The x-axis scale is time, the first peak being the first day of the month. With 9000 data points, it is not easy to display a proper time scale. The key observations:

  • The peaks in demand are about 55,000 MW in January, but peaks >50,000 MW occur throughout February and March.
  • By April, we were warming up and peak demand had dropped <40,000 MW by the end of the month.
  • A significant part of the base load is met by unvarying nuclear power.
  • The rest of the base load is met by coal that is cycled down a little at night time to help accommodate the daily demand cycle.
  • Combined cycle gas turbines (CCGT) provide little base load but most of the daily peak in demand.
  • Wind is now a significant generating source, that comes and goes, and seems to be eating significantly into the CCGT part of electricity market share.
  • The “Other” category includes French, Dutch, Irish and EW imports / exports via inter-connectors, pumped storage, conventional hydro, oil, open cycle gas turbines and “other” that combined, in conjunction with cycling the CCGTs, are used to balance the grid.

Figure 5

Figure 6

Figures 5 and 6 show the utilisation of generating capacity by source for February and March. I didn’t have time to plot these charts for January and April. Load factor is a measure of power station utilisation relative to its “name plate” capacity. For example, if a CCGT is designed to produce 500 MW, but on average only produces 200 MW throughout a year, then its annually averaged load factor is 2/5=40%. The key observations:

  • Nuclear load factor is high and relatively stable.
  • Coal load factor is high but fluctuates to help in grid balancing.
  • CCGT load factor is much lower and fluctuating a great deal, providing a huge amount of balancing service to the grid.
  • Wind load factor is also lower and fluctuating according to the prevailing weather. It is providing zero balancing service.

Figure 7

Figure 8

Figure 9

Figure 10

Figures 7 to 10 take the data displayed in Figures 5 and 6 (including Jan and April) and sort it according to load factor. The x-axis is therefore time, 1 month, but a discontinuous time series. These charts provide a profile of generating load for each month. The key observations:

  • The load factors for nuclear and coal are both very high, exceeding 100% for short spells in January (Figure 7).
  • The load factor profiles for CCGT  and wind are similar. That does not say that gas and wind are providing the same amount of electricity since the capacity for CCGT (30724 MW) is much higher than the capacity for wind (8625 MW).  Furthermore, wind provides zero balancing service whilst CCGT provides the greater part of grid balancing to accommodate the predictable daily demand cycle and the stochastic variable supply of wind.

The discussion of the implications of these observations will follow later this week. If you like the post, then please share.

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9 Responses to Gridwatch

  1. Hi Euan,

    Interesting what a large role coal plays in the balancing. Wonder if the coal plants are rated for this much variation.


    • Euan Mearns says:

      Hi Dave, in Germany, coal gets cycled even more – I’ll send you an amazing ppt by Prof Burger. In an earlier post on UK generating stats 1920-2012 I pointed out that the efficiency of coal and gas generation seems unperturbed by all this cycling – though I suspect the baseline efficiency that is unperturbed is below optimum. E

      • Hi Euan,

        Thanks. I had picked up Professor Burger’s slide show from your earlier link and used a couple of the slides in my class this week. I wasn’t as much thinking about efficiency of the coal plants as the lifetime of the plants. Maybe it is not something to worry about.


    • Hugh Sharman says:

      Dave, coal plays almost no part in the balancing. Balancing is almost 100% supplied by CCGTs. Unlike Denmark where there are no CCGTs at all and inter-connectors provide almost all the balancing against hydro in Sweden and Norway. Here in Denmark, wind power is eating up the share of CHPs.

      As in Germany, the high proportion of wind in the power system risks driving fossil plants out of business, through reduced sales and low prices.

  2. Chris Cook says:

    Interesting to compare a particular calendar month over the last x years and seeing how the mix changes with market ternds/events, such as the collapse of US gas prices leading to coal coming here.

  3. Euan, you might want to edit : “Many may recall that March was unseasonaly cold in the UK.” First of all, I don’t know that you can be sure that more than a few people can think that far back. And secondly, there is a spelling error.

    In your chart Figure 1 (unlike in other figures), the colour for wind and other are very similar, making it impossible to determine the contribution of imports etc versus wind for that month. Fixing this would be nice.

    You claim twice that wind is providing zero balancing service. Well, OK, if the grid is going to take wind power in preference to other power because it’s cheaper, or they are obliged to, then, OK, wind will not be used to balance the grid. However, looking at it from another perspective, wind power means that gas and possibly coal do not need to cycle up to meet some peaks, so perhaps your claim is not solid.

    The comparison of the installed capacity of CCGT combined cycle gas and wind is erroneous, as you cannot compare MW to MWh – it may be that at times wind power is providing more energy than gas, even though more gas-fired power generation capacity exists. This is a logical problem in your argument, and I would suggest lowers the value of your work.

    I think what you are doing is very important – we desperately need the charting you are providing. Of course, in Germany, where they take renewable electricity seriously, there are charting services of this kind coming from very senior agencies, and they are showing that wind power is displacing a significant amount of fossil fuel use – proving that wind power works.

  4. Euan Mearns says:

    I fixed the chart:-)

  5. Alister Hamilton says:

    Hi Euan,

    I’m a refugee from The Oil Drum and have just stumbled upon your website having been in the wilderness for some time!

    I’ve a couple of points to add to this post.

    What we need in the UK is a huge increase in electricity storage capacity as renewables are rolled out. I’m impressed by the potential of pumped heat energy storage as being developed by Isentropic Ltd ( in the UK. They claim low cost utility scale storage capability with 72%-80% round trip efficiency and are in the process of developing a utility scale storage machine.

    With regard to Gridwatch, figures quoted are for metered wind. There’s an additional 50% or so unmetered, according to the website.

    The UK is going through a period of rapid deployment of renewable energy infrastructure. The figure of 8.8 GW installed capacity in 2011 was up 36.7% from 2010 (BP Statistical Review of World Energy 2013) and now stands at
    10.2 GW according to the UK Wind Energy Database. Solar was 1.655 GW in 2012 (BP data) up 69.6% from the year before. So the picture is changing quite rapidly.

    I guess unmetered wind and solar will show up as a drop in demand.

    It’s quite windy in Edinburgh today – wind is now contributing 4.5 GW according to the figure on the Gridwatch website, which may actually be 6.75 GW-ish.

    Best wishes,


    • Euan Mearns says:

      Hi Alister, Good point about the unmetered wind, and of course all that unmetered solar. At times there is too much data to keep on top. I think DECC may have more comprehensive stats. And as for storage – whoever cracks utility-scale efficient storage is going to make a lot of money. Should have another post tomorrow, hope you hang around. Best E

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