Image source: TreeHugger.com.

One of the frequent criticisms of wind energy is that national distribution systems (‘the grid’) cannot cope with large number of turbines because of the variability and unpredictability of their output. Grids need to match supply and demand precisely, the critics say, and because wind varies so much it causes huge problems. Recent data from two meteorologically unusual days in Spain – the world leader in the management of renewable energy supplies – shows this assertion is almost certainly false.

• During part of 8 November, Spain saw over 50% of its electricity come from turbines as an Atlantic depression swept over the country’s wind parks. (They are so big that no one seems to call them ‘farms’.) Unlike similar times in November 2008, when Spanish turbines were disconnected because the grid had an excess of electricity, the system accepted and used all the wind power that was offered to it.
• A very different event in January of this year saw unexpectedly high winds shut down most of the country’s turbines with little warning. The grid coped with this untoward incident as well. These two events show that a well run transmission system can cope with extreme and unexpected events even with a large fraction of power provided by wind.

Over the course of this year Spain will generate about 14% of its total electricity from wind and this number is likely to rise to the high twenties by 2020. Spain is showing the rest of the world that these figures are not incompatible with grid stability. Although wind is ‘variable’, ‘intermittent’ and ‘unpredictable’, a well functioning grid system can still use wind to help stabilise electricity costs, reduce carbon emissions and improve energy security.

***

53% from wind
At some periods on the night of 8/9 November, wind provided 53% of Spain’s need for electricity. This was a new record for the Spanish system. As the country continues to install thousands of new wind turbines a year, this record will not stand for long.

Although Denmark has had similar percentages of its electricity provided by wind, the Spanish numbers are particularly significant. As its electricity transmission company, Red Eléctrica de España or REE, reminds us, the country is unusually isolated from international interconnections. It is ‘a peninsula electrically speaking, with weak electrical interconnections with the European Union’.[1] A country with limited capacity to import or export power has more issues accommodating large amounts of wind power. Denmark has international connections to cover 50% of its electricity while Spain has less than a tenth this amount. (The UK also scores extremely poorly on this dimension.)

Spain is able to manage the integration of wind power into its grid primarily because it has reasonable amounts of hydro-electricity and pumped storage.[2] Hydro-electricity can be used when winds are less than expected and pumped storage can assist both when wind is unexpectedly high or unexpectedly low.

One of the main criticisms levelled at wind is that its power is so unpredictable that huge amounts of fossil fuel generating capacity needs to be kept ready to replace it at a moment’s notice. Those antagonistic to wind believe that the carbon cost of keeping power stations in a state of what the industry calls ‘spinning reserve’ is enormous. Power stations, they say, are burning fuel so that they can instantaneously start producing electricity if and when the wind drops.

But is wind so variable that power stations need to provide immediate backup? The utterly superb REE website provides easy-to-use data to test this theory. I’ve used this data to try to demonstrate that wind production was remarkably consistent during the peak day of 8 November.[3] Not only is wind speed largely predictable with good meteorology, but REE data shows that even in the windy days of early November, the amount of electricity generated only varied gradually.

During this 24-hour period the total generated varied from about 9.3 gigawatts (9,300 megawatts) at the start, to a peak of around 11.5 gigawatts at about 14.30 in the afternoon. For most of the day, the wind output was very stable around 10 gigawatts. (The wind output estimate is provided every ten minutes on the REE website.) The mean percentage variation from one reading to the next was 0.72%. On only three occasions out of 143 observations did the output vary more than 2% between two readings.

When the wind is blowing strongly, any local variations in wind speeds tend to be balanced out by compensating changes elsewhere. A country like Spain, with over ten thousand turbines spread across a large landmass, will have low variability of electricity output from wind. As a country adds wind turbines, the degree of variability in electricity output will tend to fall. In Spain, the variations on 8/9 November represented no threat to the stability of the electricity system, even when wind was meeting half of total power demand.

Unforeseen events
The 8/9 November peak was predicted by REE. 23 January 2009 was very different. The Spanish grid was expecting very high winds from Atlantic Storm Klaus and projections were for the country’s turbines to produce about 11 gigawatts (11,000 megawatts) of electricity for most of the 23rd and the night of 23/24.

It didn’t quite turn out that way. Wind speeds were unexpectedly low on the morning of the 23rd and electricity output hovered around 9.5 gigawatts. As wind speeds rose output began to rise from about midday and peaked at about 16.00. By that time the winds were sufficiently strong to trigger automatic shut-down of many turbines in the north of the country. (The technical term for this is ‘over-speed protection’ and means the turbines cease to provide any electricity at all.) The grid hadn’t predicted this and the amount of wind power began to fall far short of what it was expecting. By 21.00 wind generation had fallen to about 7 gigawatts (7,000 megawatts), almost 4 gigawatts below the prediction for that time. Output continued falling throughout the night and only began to recover early next morning.

At the moment of minimum output (about 06.30 on the 24th), the gap between the forecast and actual wind turbine production exceeded 7 gigawatts, or the equivalent of four or five large coal-fired power stations.

This event was unusual in two separate ways. First, it was extreme. I haven’t obtained detailed records for Spain but the grid says that some wind parks experienced winds of up to 220 km/h or about 150 miles per hour. French evidence suggests that Atlantic Storm Klaus produced the most destructive winds experienced in the south-west of the country – the part just north of northern Spain – for ten years. Some French areas reported a loss of one third of all trees in some forests.

Second, the severity was not predicted. The grid was expecting very high levels of output but did not think that the speeds would reach the level that forced turbines into automatic shut-down. The combination of these two factors produced almost the most difficult imaginable set of circumstances for an electricity transmission system: wind was expected to provide a large fraction of all electric power but this electricity suddenly became unavailable. If this Spanish electricity system could manage this, it could survive almost all problems that renewable generating plants could throw at it.

And survive it did. The control centre ramped up the supply of hydro-electric power, including pumped storage, and temporarily imported power through international connections. Within a few hours of the storm’s unexpectedly powerful arrival, the system was back in equilibrium and began to export its power again by 22.00 on the 23rd, well before the period of minimum wind output. Coal- and gas-fired power stations ran hard until about 23.00 and then fell away as total demand declined during the night.

The crucial thing about wind is that it usually fades gracefully, even in extremely severe circumstances such as Klaus. Below is a chart that shows total output from Spain’s 15 or so gigawatts of wind turbines, spread across the country but concentrated along the Atlantic coasts from Vigo northwards. You will see that the decline during the passage of Klaus is almost a straight line, with only minor unexpected bumps. By 03.00, the position is beginning to stabilise. The chart logs estimated wind output every ten minutes and in only two of the 65 ten-minute periods did output fall by more than 5%. The mean percentage variation from one reading to the next was 0.72%.[*]

The maximum loss of power in any ten minutes was about 450 MW and this occurred quite late in the course of the storm, when the control room was already directing surplus electricity back into pumped storage reservoirs. The control could instantaneously reduce the amount of power being sent to pump water into high reservoirs in response to the few cases of sharp declines in wind turbine availability.

The lesson from this event is profoundly cheering. The Spanish electricity system was expecting up to about 45% of its power on the night of 23/24 January to come from wind. The outturn was about 16% for most of the night. The system handled the problem with no outages.

The implications of these two events for European wind power
Those that oppose wind power, particularly in Britain, say that wind is so unreliable as to be useless. They parade a vision of gas-powered power stations generating spare electricity just in case the wind suddenly drops. The reduction in carbon emissions is negligible, they claim, and the cost of installing turbines is huge.

None of this is true. The Spanish case histories in this article show that good grid management can integrate very large amounts of wind energy with few problems, provided that pumped storage and hydraulic power can be used for storage and international connections enable easy export and import. Second, the carbon emissions from Spanish electricity production during the peak hours of 8/9 November are calculated by REE at about 145 grammes per kilowatt hour, about a quarter of typical UK electricity. Using wind power in large volumes substantially reduces the carbon dioxide produced in electricity generation.

What about the cost of the wind electricity? The Spanish system pays wind park owners €75 per megawatt hour under most conditions and a maximum of about €90 when the overall power market is trading electricity at unusually high prices. For comparison, this is considerably less than is typically paid to UK wind farm operators from wholesale sales of power and from the supplementary value of renewable electricity credits.

The Spanish system is therefore a) improving the country’s energy security, b) reducing carbon emissions, c) costing less per MWh than the British support system, and d) incentivising the introduction of continuing huge numbers of extra wind turbines. Other countries have a lot to learn from Spain.


Footnotes
[1] Presentation to the MIT Energy Club, ‘Wind energy development in Spain’, delivered by Luis Atienza, Chairman and CEO of REE on 3 April 2009.
[2] Pumped storage reservoirs release water through turbines when power is needed. The water flows into a lower reservoir. When electricity is prospectively in surplus, the water is pumped back into the upper reservoir. These systems can usually produce electricity within a half minute of being instructed. Big reservoirs can produce gigawatts of power, but usually only for a number of hours, not days. They are particularly useful at protecting against the unexpected shutdown of large fossil fuel or nuclear stations, which can occur (although rarely) within no warning whatsoever.
[3] The REE system now monitors most individual turbines in real time. This certainly isn’t the case on other grids. Data is immediately visible on http://www.ree.es/operacion/curvas_demanda.asp (Spanish language).


[*] This sentence was added after the original publication of this article. Both graphs have also been replaced with higher quality images. No data points were changed. (Wednesday 18 November 2009.)

Mitsubishi Ecodan. Image source: Ecodan brochure.

(The information in this article has been updated by a more optimistic article that looks at the before and after experience of a ASHP installation in Oxford, Please go to http://www.carboncommentary.com/2010/08/03/1632)

Small heat pumps are increasingly used to provide space and water heating in UK homes. This trend is strongly encouraged by policy-makers and the government’s proposed Renewable Heat Incentive will add further financial support. The enthusiasm for this expensive technology should be moderated: for a home on the mains gas network, the savings in money will be small. Carbon benefits are probable but far from guaranteed. Moreover, air source heat pumps are unlikely to be able to heat many older homes effectively. Government, manufacturers, and installers need to be very much more cautious in encouraging the use of heat pumps and should use far more conservative payback assumptions. Heat pumps will eventually be a good investment for homeowners but probably not yet.

***

What is a heat pump?
When a gas is compressed, it heats up. When it is uncompressed, it cools. Imagine the simplest possible compressor – a bicycle pump. Hold your finger over the exit and push the pump handle. The air inside will get very hot. Lift your finger and let the hot air out, and it cools again. Imagine that the cylinder of the bicycle pump was inside your house but the exhaust air was vented through a window. When you pumped the bicycle pump, the chamber would get hot, and this heat would heat the room. As the air left the pump and was exhausted to the outside air, it would cool, tending to reduce (to a very tiny extent of course) the external temperatures.

This is the principle of a heat pump. The heat from the compressed gas is used to increase temperatures in one place; whereas the reverse – heat loss from the decompression – decreases temperatures in another place. Think of this as taking a block of air and separating it into a hot gas and cold gas in two separate places. When temperatures are high, you can reverse the pump, putting the cold air into the house and the hot air outside. Most heat pumps transfer the heat or cold into water that is then circulated round the house. So a domestic heat pump can, under certain circumstances, use a house’s existing network of hot water pipes and radiators. Similarly, a heat pump can provide the hot water for domestic baths and showers.

How much energy do heat pumps save?
Heat pumps look like a free source of energy and good ones are indeed very efficient. But they do need compressors and other electrically powered devices to work. (Or, in the case of the bicycle pump, the compression is provided by the person pumping. He or she will be using energy to work the pump.) So heat from heat pumps is not free. The ratio of energy used to power the pump and the useful heat output is called the Coefficient of Performance, usually abbreviated to CoP. This figure is critically important when you are assessing how much money or carbon you will save. The CoP will vary according to the air temperature and the demands placed on the pump. Broadly speaking, the greater the temperature difference between the interior of the house or the hot water supply and the outside temperature, the lower the CoP of the heat pump. A poor CoP means that you will use a lot of electricity for each unit of useful heat.

Today, attention is focused on heat pumps that use the outside air for their energy. These are called air source heat pumps (ASHPs) and are relatively easy to install in domestic houses. The unit can be attached to the wall or sit on the ground, taking relatively little space. The best ones, such as Mitsubishi’s Ecodan have a CoP of about 3-3.3 in average British conditions. For every unit of electricity used, the home gets up to 3.3 units of heating, but I’ve used the average figure of 3.15 in the calculations that follow. As heat pumps improve, this number will rise, but please don’t use the manufacturers’ figures when you are assessing them. Look for real-world examples.

Ground source heat pumps can achieve better CoP figures than their air source equivalents. But they are more expensive to install and get their ‘fuel’ from small pipes that run underneath the garden, collecting and dispersing heat energy. The garden has to be dug up to install these pipes.

Radiators versus underfloor heating
Hot water from the heat pump can be circulated using a house’s existing pipework and radiators. Unfortunately, some householders will see substantial problems. The water coming out of heat pumps is usually far cooler than from conventional gas or oil boilers. Typically, the water is at 45 degrees compared to perhaps 75 degrees from an ordinary boiler. As you might imagine, this means that radiators do not get really hot, and the amount of heat that they transfer into a room is much less. The solution is either to replace all the radiators with much larger ones with a far greater surface area, or to install a dense network of hot water pipes under the floors. In a new house with a heat pump it is almost certainly best to avoid radiators and use underfloor pipes throughout the house.

Heat pumps also heat water for showers. This water needs to be hotter, which adversely affects the efficiency (the CoP) of the heat pump. Modern air source pumps take the water up to 55 or 60 degrees, which is hot enough to bathe in.

How much do heat pumps cost?
Unsurprisingly, the cost varies enormously according to the complexity of the installation and the size of the pump. In an average-sized new house, the extra cost compared to a conventional boiler is probably between £2,000 and £3,000. To replace an existing boiler in a house already standing will add slightly more, particularly if any radiators need to be replaced. One system I have recently seen cost about £6,000 compared to perhaps £2,000 for a good condensing boiler. The government is currently offering a grant of £900, which makes a real difference but still doesn’t create an overwhelming incentive.

What does this mean for the householder?
The typical UK house on the mains gas network uses about 15,000 kWh for room heating, and much smaller amounts for water heating and cooking. If an air source heat pump has a CoP of 3.3, this means that replacing a gas boiler should significantly reduce the amount of energy used to heat the home. Here are the figures:

Energy savings from using an air source heat pump

In the example above, the electricity needed to heat the house is less than a third of a gas boiler. But electricity is far more expensive than gas for each kilowatt hour. In June 2009, the cheapest tariff on the British Gas website offers a price of just over 3p a kilowatt hour for gas and slightly less than 10p for electricity.[1] Using these rates, I calculate that an air source heat pump will save the average customer on the gas network about £50 a year. This is not a good return on the investment of several thousand pounds.

The government’s Energy Saving Trust suggests typical savings of £300 for a home with gas, but this seems unreasonably optimistic.[2] It is probably a mistake for government bodies to exaggerate the benefits of new technologies in an effort to persuade the public to adopt them.

But if you use electricity to heat your house, the savings could more impressive. Many of the five million homes off the gas network employ night storage radiators that take advantage of low overnight electricity rates. The radiators heat up at night and then give off their heat during the day. However there are two problems. First, the householder will have to put new radiators in the property, adding to the cost and disruption. Second, heat pumps usually work all the time, and not just at night. So if a householder puts in a new heat pump, she will be using both low price night electricity and very expensive daytime power. Personally, I doubt whether the savings will be much greater than £200 or £300 a year, not the £870 estimated by the Energy Saving Trust.

The CO2 savings
The CO2 savings also tend to be exaggerated. A heat pump uses electricity (largely generated from burning gas or coal) to replace a boiler that typically burns gas. The CO2 saving therefore depends on the relative efficiency of heat pumps and large scale power stations.

The amount of carbon dioxide produced by a power station depends on the fuel it burns and the quality of its generating equipment. An old coal-fired station produces a kilogramme of CO2 for each kilowatt hour. A new gas plant has carbon dioxide output of well under half this figure. The UK average varies from year to year depending on which power stations are working. As of June 2009, the most recently published figure by the Carbon Trust suggested an average figure of 0.54 kg of CO2 per kilowatt hour. This figure is derived from a five-year average of power stations supplying the National Grid, mixing coal generation with gas, nuclear, and wind.

We can easily work out the CO2 savings from running a heat pump to heat a typical house:

Carbon dioxide savings from heat pump use in the average home

This is a more substantial reduction than the financial saving, cutting emissions from heating by about a fifth. Since home heating is often the single most important source of emissions, a heat pump may be worthwhile. But the cost of the pump for every tonne of CO2 saved is very high.

Cost of a heat pump per tonne of CO2 saved

The issues with heat pumps
In some countries – such as Switzerland and Sweden – heat pumps are very common. In these places, insulation standards have been high and heat pumps can heat houses even in very cold weather. In countries with low-carbon electricity supplies, like Switzerland, which has large amounts of hydro electricity, there is a strong reason to move to using electric power rather than gas or oil for heating. For the UK, this is not the case. In recent years, we’ve actually seen a slight increase in the carbon dioxide produced in electricity generation as the nuclear power stations have become increasingly unreliable and large amounts of coal have been burnt rather than cleaner gas.

So the climate argument for using heat pumps in the Britain does rather depend on whether we do successfully develop new and low-carbon sources of electricity. The attractiveness of using heat pumps will rise as we switch to wind energy, biomass, and other low-carbon sources of power. However, I think it probably makes sense to wait for this to happen rather than buying a heat pump now.

There are some other issues. Experience from the first ASHPs suggests that some do not heat the house effectively in winter. A gas boiler has enough power to pump huge amounts of heat into a house in a short time. You can turn it on at five o’clock in the morning and the house will be warm for when people get up. Heat pumps aren’t like this. They are kept on constantly, but deliver heat at lower levels. This is fine if your house is well insulated because the heat will remain. But in a draughty older house the heat will leak away and the lack of warmth may be a problem, particularly when outdoor temperatures have fallen rapidly. One householder intending to install a heat pump responded to this point by saying to me that his home would also have electric immersion heaters to increase the temperature in the central heating system when necessary. This is an unusual configuration but it may work – although at the price of higher electricity bills and reduced carbon savings.

It should be stressed much more prominently in the literature advertising air source heat pumps that they are not suitable for many houses built more than ten years ago. Before this time, insulation standards were simply too low for heat pumps to maintain reasonable temperatures in the coldest weather.

As we mentioned above, in many houses the installer should also think about replacing small radiators for much larger ones with greater surface area. This would help spread the heat effectively, but because it would be costly and disruptive, most companies selling ASHPs don’t push this option. Ideally, householders should replace radiators entirely with underfloor piping.

Another disadvantage may become evident when the heat pump is heating hot water for bathing. Heating enough water for two baths will take almost an hour with a standard 8.5 kW pump. During this time, the heat flowing into the central heating system will inevitably be much colder because all the energy from the pump will be going into the bathing water. In a well insulated house, having the central heating off for an hour shouldn’t matter very much, but in older homes the impact will occasionally be unpleasantly noticeable.

A proponent of air source heat pump responds
I rang Ice Energy, one of the largest installers of domestic heat pumps, to discuss some of these concerns. Andrew Sheldon gave me his company’s response:

• Small savings: At current gas and electricity prices, this may be the case. But, Andrew argued, gas prices are likely to rise relative to electricity prices. I think this is possible, but it is equally likely that the reverse will be true as the government forces the development of higher cost sources of electricity such as offshore wind. Andrew also said that the Renewable Heat Incentive, to be introduced in 2010 or 2011, would probably enable heat pump owners to claim money. He mentioned 10 or 12p for each kilowatt hour of heat generated, implying a payment of over £1,000 a year for an average-sized house. Even 2p would make the financing of heat pumps look more attractive.
• Limited carbon savings: The UK is on track to decarbonise its electricity supply by 2030. Once this has happened, carbon savings will be very substantial.
• Worries over heating on cold days: A well insulated house should not suffer from low temperatures. Newly built houses with underfloor piping should see large financial savings and high levels of comfort.
• The high price of heat pumps: Andrew said we should take into account the longer life of heat pumps, which will last more than 20 years. They will also need lower levels of routine yearly maintenance.

He also stressed the greater safety of heat pumps. The radiators and bathing water temperatures are never dangerously hot, minimising the risk to the elderly and young children. The constant heat in the winter also means better indoor air quality because the high temperatures and powerful convection currents close to radiators in today’s homes tend to result in high levels of dust in many rooms, particularly in older houses.

When the UK has built an infrastructure of low-carbon electricity generation, we will need to find ways of reducing the carbon dioxide emitted from heating buildings. For domestic homes, heating is much more important as a source of CO2 than electricity use, so the savings could be very important. Heat pumps and domestic fuel cells (such as those in testing from Ceramic Fuel Cells) may be the most important ways of cutting emissions from houses. But at the moment, the economics of heat pumps are not overwhelming attractive. Householders in existing properties, particularly those living in older homes, should be very wary of installing an ASHP.

(This article will form part of the 2nd edition of How to Live a Low-Carbon Life to be published by Earthscan in February 2010.)

Footnotes
[1] These prices are ‘Tier 2’ rates which apply to all consumption of gas and electricity above a certain minimum level. They exclude some small discounts because I couldn’t understand how these reductions worked.
[2] Energy Saving Trust figures downloaded from http://www.energysavingtrust.org.uk/Generate-your-own-energy/Air-source-heat-pumps on 10 June 2009.

Copyright: Monkey Business - Fotolia.com.

Electricity demand has fallen substantially in the last couple of years and shows no sign of recovery. The cause could be:

• The impact of economic slowdown
• Better energy efficiency
• Demand reduction because of the high prices seen in recent years.

If the cause is the contraction in the economy, then we can expect electricity use to rise again when growth resumes. On other hand if it is energy efficiency, then it is reasonable to expect that the reduction will persist. Electricity demand is usually thought to be insensitive to the price of power. If it is high prices that are driving usage reductions, we have gained important information about how to reduce electricity use, and thus carbon emissions.

The conclusion of the analysis in this short note is that almost all of the reduction in energy demand comes from cuts in usage in big industrial and commercial users. This means that the most likely cause of the cut is the fall in economic activity. Household demand seems to have remained about constant.

***

The data
National Grid publishes demand data for every half-hour period. The latest publicly available information covers January – March 2009. Manipulation of this data is made difficult by the varying dates of public holidays and weekends across different years, but broad analysis is possible.

Demand reductions between 2008 and 2009 are given in this table:

This table might seem to suggest an accelerating decline. This would not necessarily be the right conclusion. Electricity demand is affected by temperature, which was unusually low in January and February and high in March.

The following table compares England temperatures in 2009 and 2008:

So the underlying reduction in January and February 2009 may be understated, while the precipitous fall in electricity use in March 2009 is partly an artefact of the relatively high temperatures in the month.

Can we say anything about what is driving these reductions?
National Grid demand data is provided for each half-hour period. So we can compare the pattern of reduction for each part of the day.

I looked at March in detail. I excised the data for Easter in 2008 (when it fell in March as opposed to April in 2009) and the comparable days in 2009. I ensured that the 2008 and the 2009 data contained the same number of weekdays and weekend days. This allowed me to make a reasonably fair comparison between the two months.

I then calculated the average reduction in use at each half-hour point in the day. So, for example, I obtained a figure for the average electricity use at 4.30am for March days in 2008 and 2009.

Here is the pattern of reduction across the 48 half-hour periods in a day:

March 2009 UK electricity demand as percentage of March 2008,
by time of day

This chart shows that electricity use reduction varies from almost 10% (at around 4am) to less than 6% in the morning and early evening.

Someone from the electricity industry looking at the chart above will immediately notice something. The periods of least reduction from 2008 to 2009 are also the periods of highest electricity demand from domestic homes. The chart below is scraped from the Environmental Change Institute’s study ‘The 40% House’. It shows the pattern of daily winter demand for UK electricity in 2002 and splits it into domestic and non-domestic. Demand peaks at about 7.30am and 6pm. These are the periods of least reduction in electricity demand between March 2008 and March 2009:

Source: Environmental Change Institute.

What does this mean? We can’t be completely sure, but the most likely explanation is that UK domestic demand is virtually unchanged while industrial demand has fallen very sharply.

Home use of electricity is about one third of total UK use. Industry is another third, while offices, shops and other commercial installations take the final portion. But as you can see from ECI chart above, the domestic proportion is far higher in the morning (toasters and last minute ironing) and early in the evening (TVs, supper, and the washing machine). So if domestic demand is largely unchanged, we’d expect to see far lower reductions in aggregate electricity demand at these points in the day. And that is exactly what we do see.

Conversely, at 4am when domestic demand is only about 20% of the total, but the big industrial electricity users are still using power for making steel, plastics, bread or whatever, aggregate demand is down almost 10%. This cut almost certainly arises from lowered levels of economic activity, and it might be augmented by the energy use reduction plans implemented by many large industrial users.

All in all, my best guess is that the March data is consistent with about a 10-12% reduction in electricity use in industry, perhaps 6-8% in offices and shops, and a very small cut in consumption in homes.

Why is this disappointing? We might have hoped that the squeeze on personal incomes, high electricity prices, and improved energy efficiency in appliances would by now be making a measurable impact on electricity use in the home. But there’s no evidence of this from the data. Second, we might also have been optimistic that energy reduction programmes in some industries would have reduced use. But, if anything, the reverse is true. Latest UK data (Index of Production for Q1 2009, published 12 May) suggests that industrial output was down 12.1% compared to 2008, slightly more than my estimate of the fall in electricity use. The bad news is that my very rough analysis of the data shows that we can explain all the fall in electricity consumption as a result of the economic recession and none as improved energy efficiency or a reduction in waste. When growth resumes, we’ll probably see electricity use accelerating at a rapid rate. The implications for carbon emissions are, of course, severe.