House of Commons - Trade and Industry

Select Committee on Trade and Industry First Report

2 Local energy's potential

10. Most electricity and heat in the UK is produced from coal, gas or nuclear energy, with a small but growing contribution from renewables such as wind and hydro. A future energy mix where local energy made a significant contribution to our electricity and heating needs would, however, incorporate a much broader range of technologies. The majority of these would either be renewable or would make more efficient use of fossil fuels than do current large-scale power stations. Yet, if the UK is to produce a large proportion of its energy locally in the long run it must begin building capacity today from virtually a standing start. In this Chapter we outline the main technologies and fuel sources that come under the umbrella term of 'local energy'. We go on to examine the possible benefits that greater use of local energy might bring about, for example by reducing carbon dioxide emissions. Finally, we consider the long-term potential contribution that local energy could make to the energy mix.

The technologies

11. The different ways of producing local energy can be split into three categories: those which generate electricity alone, those which produce only heat, and combined heat and power (CHP), which enables the local use of the heat resulting from combustion-based electricity generation.

12. For electricity-only generation the two main technologies are wind and solar photovoltaic (PV) systems. Wind turbines vary in design, although the most common ones use three blades, mounted on a horizontal axis, which drive an electricity generator. There have been significant technical advances over recent years. One kilowatt units are now available for household installation, while the largest turbines can have a capacity of up to five megawatts. The second main technology, solar PV, generates electricity from sunlight using roof-top panels or tiles. The panels usually contain two or more layers of silicon, which produce an electrical charge when exposed to light. Solar power has been in use for more than half a century and in a variety of contexts, varying from pocket calculators to communication satellites.[8] A third, and rather more niche, form of local energy for producing electricity is hydropower. Here, the vertical flow of water is used to drive a turbine. Potential energy sources are, by definition, confined to wherever there is a flow of water from a higher level to a lower level, such as strongly flowing streams, river valleys or hilly areas.[9]

13. For heat-only local energy production there are three main technologies: solar thermal, heat pumps, and biomass. Solar thermal systems use roof-top tiles to capture thermal energy from the sun, which is used to heat water. About 8 m² of tiling can provide roughly two thirds of the hot water requirements for an average three bedroom home.[10] Heat pumps capture thermal energy stored in the ground, water or air to supply hot water for heating purposes. They operate on the same principle as freezers or air conditioners, only in reverse. The term 'pump' is something of a misnomer as the system moves heat rather than pumps it. Finally, space or water heating can be generated from biomass stoves or boilers, which burn wood or other fuels such as energy crops (for example, willow or miscanthus). Whilst the technology for distributing heat produced in this way has advanced in recent years, the principle itself is clearly not a new one—for as long as humanity has been able to create fire, people have used it to keep themselves warm.

14. Finally, combined heat and power (CHP) units, also known as cogeneration, use either natural gas or biomass as a fuel to provide electricity and heating simultaneously. Whereas conventional large power stations emit heat into the environment as a by-product of electricity generation, CHP systems capture this thermal energy to use locally. There is nothing new in this idea. Some larger power stations, such as the old Battersea power station, delivered heat to local homes. Depending on the size and location of the plant, this may be purely for domestic use, in the case of micro-CHP, or to provide office or community heating through a heat distribution network. By-product heat can also be utilised in absorption chillers for cooling, in other words, for producing 'cold'. This is known as trigeneration, examples of which are currently operating in Woking. Lastly, fuel cells also offer the potential to provide CHP in the long-term. These devices generate electricity from the reaction between a number of chemicals, without the need for combustion and without producing noise or gaseous pollution. Those which use natural gas could offer greater efficiency gains than conventional CHP, although the technology appears still to be a long way from being commercially viable.[11]

15. Local energy can be produced in a variety of ways, using either renewable or fossil-fuel sources. Each has the potential to generate energy, whether in the form of electricity or heat, at or very near to the point of consumption. In many cases these are not new energy sources. Indeed, humanity's use of biomass, wind, and hydro energy pre-dates the use of fossil fuels. What is new today is the technology available to harness these sources of energy and the way in which their use in a modern context presents newly perceived benefits by reducing carbon dioxide emissions and contributing to energy security.

Benefits of local energy

16. In the evidence we received, proponents of local energy described various advantages in shifting away from our current centralised energy infrastructure towards one based increasingly on local energy. The Government's Energy Review report, The Energy Challenge, states that "we now face two immense challenges as a country—energy security and climate change". In various ways, local energy has the potential to contribute to tackling both of these issues, as well as presenting possible additional economic benefits, for example in reducing fuel poverty.

REDUCING CARBON DIOXIDE EMISSIONS

17. There are three main ways in which increasing the UK's local energy capacity can help to reduce carbon dioxide emissions. First, it can do so directly by offsetting the use of fossil fuels in large-scale power stations, or by using fossil fuels more efficiently. Many local energy technologies, such as wind, solar and hydro, are renewable. For example, the installation of a roof-top wind turbine at a site with reasonable wind speeds could reduce carbon dioxide emissions by 10 to 15% for an average household.[12] There would be some emissions associated with the life-cycle of the generating equipment (such as in its production and installation) but these are not significant compared to the emissions that arise from either gas or coal-fired generation.[13] There are some local energy sources, namely CHP, which do use fossil fuels. The most common forms of micro and small-scale CHP currently run on natural gas. Here, carbon dioxide savings may arise by making use of the heat produced during electricity generation, rather than emitting it into the environment, and reducing the need to use further electricity or gas to produce heating separately in homes or businesses. In so doing, CHP can increase the overall efficiency of fossil fuel use to more than 75%, as opposed to around 40% for conventional large-scale electricity generation.[14]

18. Achieving the type of efficiencies for CHP often quoted by advocates of the technology requires a consistent local source of demand for the heat produced. Yet, in many settings, heat and electricity needs do not always coincide. For example, in a household fitted with micro-CHP, demand for heating will be fairly low during the summer months and high relative to electricity demand during winter. For larger-scale systems, such as community or commercial schemes, this is less of a problem because the demand for heat and electricity is steadier. Trigeneration technologies are also suitable in these settings because they allow waste heat to be transformed into cooling energy.

19. Most research on the estimated carbon dioxide savings of micro-CHP is theoretical. For example, a report by the Sussex Energy Group suggests that micro-CHP which offsets electricity from combined-cycle gas turbines, produces 10% less in carbon dioxide emissions. This rises to 30% if coal-fired generation is displaced.[15] By contrast, there is relatively little empirical evidence on the actual carbon dioxide savings of micro and small-scale CHP. One study by the Carbon Trust has reported mixed results.[16] For domestic micro-CHP its interim findings suggested: "there is unlikely to be a significant carbon emissions reduction opportunity from wide deployment of the technology at this stage in its evolution". On the other hand, the Trust reported a much stronger performance for small-scale CHP in businesses, where it found clear evidence of emissions savings. The contrasting results stem partly from the differing pattern of energy use in homes as opposed to firms, but also from the lower technical efficiency of micro-CHP for producing electricity relative to small-scale generating plants. While it is worth noting that many of the technologies trialled in the study are still in their infancy, the results to date suggest that the carbon dioxide saving potential of CHP is highest in settings where there is sustained and simultaneous demand for the heat and electricity produced. This will be primarily the case for community schemes, commercial centres or larger dwellings. In many households CHP has the potential to lower electricity demand, but only when the boiler is producing heat and mainly during the winter months.[17]

20. The second way in which local energy has the potential to reduce carbon dioxide emissions is by decreasing electricity network losses. When electricity is transported across distances the laws of physics dictate that a proportion of it is lost as waste heat. Overall, this amounts to 7.5% of electricity generated in the UK. About 1.5% of losses occur in the transmission system and 5.7% on the distribution networks, with the rest attributed to meter fraud or theft. In 2005, UK losses amounted to over 30 terawatt hours of electricity—roughly equivalent to the output of Drax, the country's largest power station.[18] Electricity produced on-site, at or very near to the point of use, does not come via either the transmission or distribution networks, and so the argument is that local energy has the potential to reduce the amount of energy wasted through network losses.[19]

21. Clearly, the exact level of any carbon dioxide savings from reduced losses is dependent on the type of local energy generation in place, its location, and the kind of large-scale electricity source it displaces. One study by the DTI, looking specifically at household-based local energy, estimated that achieving a capacity of almost 8 gigawatts by 2020 could reduce annual network losses by about 0.8 terawatt hours.[20] In itself, this would be a significant carbon dioxide saving if it offset fossil fuel-based electricity. It would, however, only represent a 3% reduction in network losses over current levels, because even a very large expansion of local energy capacity will not preclude the continued need for electricity supplied through the transmission and distribution networks. So long as most local energy sources are unlikely to perfectly match local demand, for example when it is overcast or there is no wind, households will need to import electricity from the distribution networks. Similarly, there will be times when local energy generators are exporting excess electricity to the networks.[21] Overall, while local energy offers some potential for reducing network losses, it is misleading to suggest such losses would be very significantly reduced. Indeed, the Energy Networks Association outlined plausible situations where network losses might actually increase as a result of greater local energy capacity.[22]

22. The third means by which local energy may reduce carbon dioxide emissions is through the potential it has to raise energy awareness amongst those who install systems on their premises, therefore acting as a catalyst to changing the way consumers view their energy. For example, there is evidence that households that install local energy schemes alter their behaviour in other ways, adopting additional energy saving measures, such as insulating their homes properly and turning off lights. One industry representative cited evidence from Germany of households adopting this behaviour, and reducing their energy usage by between a quarter and a third.[23] Where individuals have actively acquired local energy systems, such complementary behaviour is hardly surprising. What is interesting is the reaction of households that have obtained such technologies passively, for example where social landlords have fitted them to their properties. Research conducted by the Sustainable Development Commission has shown that, in these situations, people often demonstrate greater energy awareness than comparable households that have not had such systems installed. The limited evidence in this area, however, suggests this change in behaviour is by no means universal amongst passive adopters, often because of a lack of understanding of the equipment that has been fitted.[24] This highlights the importance of educating users at the time of installation—an issue which we discuss further in the next Chapter.[25]

23. Whilst local energy can contribute to reducing carbon dioxide emissions it must also be emphasised that it is not the only way of doing so, nor is it necessarily the most cost effective. As we noted in Chapter 1, the Energy Review concluded that a multi-pronged approach to tackling the causes of climate change is necessary with action on various fronts, including energy efficiency measures and potentially through new nuclear build. In the future, carbon capture and storage or fusion power may also present viable solutions instead of, or in addition to, local energy.[26] Although we should not think of any of these options as being mutually exclusive, in developing policy it is important for the Government to bear in mind the underlying cost per tonne of carbon dioxide saved for any measure targeted at the causes of climate change. For example, in terms of local energy's ability to reduce carbon dioxide emissions cost effectively, it almost goes without saying that energy efficiency offers better value-for-money, since many measures have little or no cost attached to them.[27] Several witnesses emphasised that, as a starting point for tackling the causes of climate change, energy efficiency measures were the 'low hanging fruit', potentially able to reduce the UK's carbon dioxide emissions by 20% with comparatively little cost.[28] The difficulty is in persuading energy users to realise this.[29] On the other hand, evidence we received does suggest that the capital cost of a large-scale deployment of local energy could be significantly less than an equivalent amount of nuclear power, which is also a low-carbon energy source.[30] In a liberalised energy market, however, it may still be easier for the Government to provide incentives for the construction of relatively few nuclear power stations than to change the behaviour of millions of UK households.

24. Local energy has the potential to reduce carbon dioxide emissions by displacing the use of fossil fuels, decreasing network losses, and increasing energy awareness amongst users. The scale of these benefits, however, is dependent on the types of technology used and their location. For domestic installations, local heat production such as solar thermal systems or ground source heat pumps will often be just as beneficial as electricity generation. There are some situations involving micro-combined heat and power (CHP) where local energy systems will not necessarily lead to a reduction in carbon dioxide emissions. Moreover, local energy must be considered as part of a multifaceted effort to tackle the causes of climate change, in which there are other means of reducing emissions. In particular, energy efficiency measures offer better value-for-money in the short run. As such, the Government should remain mindful of the underlying cost per tonne of carbon dioxide saved in developing policies to ensure that its approach is cost-effective.

PROMOTING ENERGY SECURITY

25. Local energy could enhance the security of the UK's energy supplies by increasing the diversity of sources from which it can produce electricity and heating. The UK is set to become increasingly dependent on gas imports in future years as North Sea reserves diminish. Although imported gas comes from a number of countries, including Norway, the Netherlands and Qatar, an energy mix that draws from a range of different fuel inputs inevitably enhances the security and stability of our system.[31] For example, a reduced role for gas in the production of electricity would decrease the impact gas prices have on the market price of electricity. That said, the extent to which energy security is strengthened is dependent on the type of local energy source adopted. Wide scale take-up of micro and small-scale CHP, powered by natural gas, would contribute less to reducing our dependency on gas imports than would renewable forms of local energy.

26. While we received evidence highlighting the potential for local energy to provide baseload generation and backup in the event of distribution failure,[32] we also took evidence that suggested increased use of local energy might act to reduce overall energy security.[33] For example, some renewable technologies, such as solar and wind power, are intermittent. What is more, their output is difficult to predict, being largely dependent on the weather. This means that backup capacity must be available for situations where owners of local energy systems have to import energy. Yet, a big expansion of local energy capacity may actually create a disincentive for the market to invest in new large-scale generating capacity that would mostly operate on standby. This would reduce the availability of flexible generators able to balance supply with demand in the system. While this is a potential risk, it is worth remembering that larger-scale renewable technologies pose the same problem, as does the inflexibility of baseload nuclear energy.[34] In other words there are possible system costs attached to most forms of low-carbon energy. Also, energy security within a more modular, decentralised energy system will, to a large extent, require network operators to engage in more active and intelligent management of their networks. We return to this issue in Chapter 7.

27. Greater use of local energy could, prospectively, increase the security of the UK's energy supplies by drawing on a more diversified range of fuel sources, many of which are renewable. It will still, however, require the presence of backup capacity when local supply fails to meet local demand, and for the time being, this is likely to use fossil fuels. In the future more active network management of the UK's energy systems will be necessary to balance supply and demand and ensure that both small and large-scale generating assets are able to operate cost-effectively.

ECONOMIC BENEFITS

28. In addition to reducing carbon dioxide emissions and increasing security of supply, local energy presents some potential economic benefits. For example, we received evidence from Ofgem, National Grid and the Micropower Council suggesting that it can help alleviate fuel poverty.[35] This is because, in the case of renewable technologies, such as solar thermal energy or wind-generated electricity, once installed, running costs for these systems are comparatively low. CHP, in settings where it offers a more efficient use of fossil fuels than, say, a condensing boiler, can also reduce domestic fuel costs. Local energy systems can also help those people who have otherwise hard to heat homes, and those not able to be connected to the gas or electricity grid.[36]

29. We note, however, that at present most local energy technologies are associated with large initial capital costs. This makes it unlikely that households suffering from fuel poverty will have the resources to make such investments. There are schemes in place to reduce the costs of local energy for consumers, though few of these are targeted specifically at those experiencing fuel poverty. There is scope in some areas though, for example, where innovative social landlords might install local energy systems for their tenants. If local energy is to make a significant contribution to the UK's energy mix in the long-term, it can only do so by engaging all parts of society, including those in fuel poverty.

30. A second, although relatively minor, potential economic benefit from greater use of local energy could be through the avoidance or deferral of electricity network investment.[37] This would be brought about through a reduction in peak demand and average annual demand across the networks. A study by the DTI estimated that, for a scenario where microgeneration produced just over 39 terawatts of annual generation in 2020 (equivalent to 10% of UK electricity supply today), the net benefit of deferring network investment and system operation costs could be around £35 million per annum.[38] Although this estimate is subject to a number of assumptions, it is not large relative to the billions of pounds worth of investment required in the UK's energy networks during the coming years.

31. Local energy presents additional economic benefits in terms of tackling fuel poverty and reducing network costs. The extent to which those in fuel poverty can capture these benefits is uncertain, though, because of the current high capital costs of local energy systems. Also, estimates of the total savings on network investment and operating costs are small, and do not of themselves provide a rationale for encouraging local energy.

Current capacity levels

32. As a proportion of the overall energy mix, the contribution of local energy is very small, but growing. Table 1 below shows the number of local energy installations in buildings currently in operation in the UK. To date, solar thermal is the most widespread, accounting for roughly 77 gigawatt hours of domestic heat generation and 172 gigawatt hours for swimming pools and other applications in 2005. The use of solar heating has risen by 165% in the last five years.[39] Total solar PV capacity amounted to just 10.9 megawatts in 2005, up from 8.2 megawatts the year before.[40] However, capacity figures across other technologies, such as micro-hydro and micro-wind, are still negligible. The story is only slightly more optimistic when we look at larger-scale CHP. Here, the UK has 5,792 megawatts of electricity capacity across 1,532 schemes, with a heat capacity of 12,396 megawatts in 2005. However, growth in this sector has stagnated in the past five years. Also, the vast majority of CHP is in industrial use—take-up amongst residential or commercial users is currently quite small. That which is installed in communities, in settings such as hotels, leisure facilities and hospitals, amounts to just 6% of total CHP capacity.[41] Table 2 provides a breakdown of CHP in non-industrial use.

Table 1: UK local energy installations in buildings (2005)

Technology	Number of installations
Micro-wind	650
Micro-hydro	90
Ground source heat pumps	546
Biomass boilers (pellets)	150
Solar water heating	78,470
Solar photovoltaic	4,301
Micro-CHP	990
Fuel cells	5
Total	82,202

Source: Department of Trade and IndustryTable 2: Number and capacity of CHP schemes installed in non-industrial use by sector (2005)[42]

	Number of schemes	Electrical capacity (MWe)	Heat capacity (MWth)
Leisure	419	45.7	71.9
Hotels	302	38.9	62.6
Health	212	117.9	210.0
Residential group heating	45	42.9	97.5
Universities	36	42.7	85.7
Offices	26	20.0	22.7
Education	21	10.2	18.0
Government estate	14	12.2	18.1
Retail	12	2.6	4.1
Other	5	14.8	22.8
Total	1,092	347.9	613.3

Source: Department of Trade and Industry, Digest of United Kingdom Energy Statistics, 2006

33. Overall, local energy currently contributes a very small proportion of the UK's supply of electricity and heat—less than 1%—reflecting the highly centralised structure of our energy system.

What can be achieved?

34. Despite the fact that the UK's installed capacity of local energy systems is very low, there is potential, in theory, for it to contribute a large proportion of the energy mix in the long-term. For example, the Renewable Energy Association noted a study suggesting that if the UK were to cover the facades and roof spaces of its existing buildings with photovoltaic (PV) panels it would generate enough electricity to meet all the UK's existing demands.[43] The UK is also quoted as having the best wind resource in Europe.[44] In addition, roughly 1.3 million homes change their gas boilers each year.[45] Centrica estimate that micro-CHP systems could displace as much as 30% of this turnover by 2015.[46]

35. Be that as it may, most forms of local energy have characteristics that are not suitable for all locations or consumption profiles.[47] For example, micro-wind power's potential is better suited to rural areas than built-up sites, because of the likely screening of turbines.[48] Indeed one witness told us the technology was "in danger of being oversold".[49] Elsewhere, solar photovoltaic and thermal systems operate best on south-facing roofs or walls, which are not overshadowed, while, as noted earlier in this Chapter, micro-CHP is better suited to larger dwellings with high and consistent heating needs. This suggests that, while the overall potential of local energy is large, not every technology is appropriate for all homes, businesses and communities.

36. Crucially, it must also be borne in mind that most local energy technologies are either too expensive for most consumers, or not even market-ready.[50] As with all new technologies there will always be a number of early adopters who choose to install local energy systems simply because they are new, or because they wish to 'do their bit' for the environment.[51] But until costs come down, or the price of energy from other sources rises markedly, local energy systems will only attract a niche market.[52] It is for this reason that much of the evidence we received predicted, at best, incremental growth in the UK's installed capacity of local energy for the foreseeable future.[53] This finding is important because the UK faces a serious capacity gap in the short to medium-term as around 30% of its large-scale generating capacity will disappear in the next 20 years as the current nuclear fleet is gradually decommissioned, and the EU's Large-Scale Combustion Directive brings about the closure of many coal-fired power stations.[54] Given the current slow rate of growth in the UK's local energy capacity, it is highly unlikely that local energy alone will be able to plug the gap, which will appear in the coming years. Indeed, there are already signs that new large-scale combined cycle gas turbines and coal-fired power stations will provide the bulk of the UK's new generating capacity in the near future.

37. Nevertheless, even with only gradual growth, over the long-term it could still be possible to achieve a sizeable increase in the amount of local energy, given certain conditions. The Energy Saving Trust (EST) has attempted to estimate the contribution household local energy technologies could make to the energy mix over the next 50 years.[55] Its analysis models the interaction of market growth and potential declining costs for local energy over time. This is combined with assumptions about government implementation of a number of policy interventions to support the take-up of local energy by households. These include regulatory changes (for example with regard to planning), capital grant support, and the introduction of an electricity pricing regime such that households receive an equivalent price for electricity they export to the network to that which they pay for electricity they import. Under these conditions, the EST estimates that domestic local energy systems could deliver all household electricity needs, with excess being exported to the grid, as well as more than half of household heating demand by 2050. This would be equivalent to 30 to 40% of the UK's electricity needs. The main contributors would be micro-CHP, followed by micro-wind and photovoltaics. Achieving this level of penetration would reduce our annual carbon dioxide emissions by 15%. Interestingly, the Trust's analysis estimates that local energy installations in homes could account for 20% of UK electricity generation in 2050 without any government intervention at all, simply on the basis of these technologies becoming more cost-effective over time.

38. The EST's estimates have been criticised by commentators, including EDF Energy and the Energy Networks Association, for being too optimistic.[56] For example, the analysis assumes a constant demand for electricity over time. Its assumptions about the extent to which the cost of local energy production may fall over time might also prove unrealistic. As one witness told us, with regard to how costs might evolve, "it is very, very difficult to tell because there are so many unknowns".[57] Nevertheless, the Trust's 30-40% estimates should not be interpreted as a prediction of what will happen in the future. Rather, it gives us an idea of what might be possible if action were taken to tackle the various barriers to local energy take-up. This is the subject of the next Chapter.

39. Looking at a community level, there is less evidence available of the potential for larger CHP schemes. A significant proportion of the UK population lives in high-density urban areas, the steadier heat demands for which make community-CHP schemes more viable than in rural settings. For example, over a quarter of the estimated potential for existing buildings is in London, with 12 other major UK cities accounting for another 60%.[58] Even in cities, however, retro-fitting existing buildings with district heating schemes would prove very expensive. This suggests that the greatest potential for community-scale projects is in developments of new construction, where systems can be built in from the start. Long-term projects such as the Thames Gateway offer a clear opportunity in this regard.[59] There may also be scope for retro-fitting schemes in some high-rise flats. These constitute almost a million dwellings in the UK. Overall, estimates of what can be achieved vary significantly. One study suggested the cost-effective potential of community-CHP could be around 2,300 megawatts of capacity by 2010.[60] However, given that over 80% of current homes are either houses or bungalows, the majority of the potential for heat through local energy sources would seem to be through household micro-CHP, provided the technology can prove itself an effective means of reducing carbon dioxide emissions.[61]

40. Local energy systems, such as CHP, wind and solar photovoltaics, are suited only to certain locations or consumption patterns. In addition, most local energy technologies are not yet cost-effective, reducing the potential for dramatic take-up in the near future. For community-CHP projects, assessments of the potential vary. Though a large number of urban dwellings would suit this technology, cost-effective implementation is likely to be limited to developments of new build. However, the UK's potential resource of local energy is large. If costs fall, and/or prices of energy from other sources rise, and certain government interventions are put in place, local energy could contribute a sizeable proportion of the UK's energy mix in the long run. One estimate, looking specifically at household installations, puts this in the range of 30 to 40% of our electricity needs by 2050. Local energy is a developing concept with real potential, but it cannot make a significant contribution in the next decade to closing the capacity gap created by the decommissioning of coal-fired and nuclear power stations—local energy is not a panacea that will 'keep the lights on'.

8 Q 69 (Sharp UK) Back

9 Department of Trade and Industry, Distributed Energy-A call for evidence for the review of barriers and incentives to distributed generation, including combined heat and power, November 2006 Back

10 www.solarcentury.com Back

11 Appendix 36 (Micropower Council) Back

12 Q 10 (Sussex Energy Group) Back

13 Parliamentary Office of Science and Technology, 'Carbon footprints of different electricity sources', July 2006 Back

14 Department for Environment, Food and Rural Affairs, The Government's Strategy for Combined Heat and Power to 2010, April 2004 Back

15 Sussex Energy Group et al, Unlocking the Power House, October 2006 Back

16 The Carbon Trust, The Carbon Trust's Small-Scale CHP field trial update, November 2005 Back

17 Appendix 47 (RWE npower) Back

18 Department of Trade and Industry, Digest of United Kingdom Energy Statistics, 2006; 1 terawatt hour = 1,000 gigawatt hours = 1,000,000 megawatt hours Back

19 Appendices 2 (Airtricity), 3 (Association for the Conservation of Energy) and 16 (EDF Energy) Back