HC 562 The effect on energy usage of extending BST

Memorandum submitted by the Government (BST 01)

The following memorandum provides written evidence from the Department for Business Innovation and Skills (BIS), the Department for Energy and Climate Change (DECC) and the Department for Transport (DFT) on the effect on energy usage of extending British Summer Time.

The current summertime arrangements for the UK involves moving the clocks forward one hour on the last Sunday of March each year so that were are on Greenwich Meantime (GMT) +1 and then back an hour on the last Sunday of October back to GMT. While on GMT+1, this is classed as British Summer Time. The twice-yearly change in time occurs in accordance with EU legislation The 9th EC Directive on Summer Time which harmonised the dates clocks change across EU member states.

In response to the Committees request for evidence in relation to the effects on energy usage of extending British Summer Time which would mean being on GMT +2 during he summer and GMT +1 during the winter, the following is provided.

Summary

1. In summary, although we might expect overall energy use to be reduced by extending British Summer Time ("BST") the effects are likely to be small in magnitude, and may even be uncertain in direction. The most significant effects are likely to be associated with lighting demand as demand switches from the evening to the morning.

2. However the evidence quantifying these effects is not strong enough to conclude either way what the impact on the overall demand would be. On the one hand the working day is more aligned with natural daylight leading to reduction in demand, however there are also complex behavioural factors to consider such as such as the fact that households may be more likely to turn lights on when it is dark than off when it is light.

3. Evening peak electricity consumption may flatten (i.e. peak evening demand shifts to the morning) as a result of extending BST during the winter months which could be beneficial to security of supply. However, evening peaks between Great Britain and France may become more aligned, with implications for prices and security of supply in situations of low generation capacity margin.

4. The impact on gas demand for space heating is likely to be limited, but a flattening of peak electricity consumption, could, depending on the relative fossil fuel prices, result in a fall in gas demand for electricity generation which again could be beneficial for security of supply.

5. The effect on carbon budgets is dependent on the change in overall demand and is therefore likely to be limited. To the extent that extending BST reduces energy consumption, this may reduce the cost of meeting the renewables target.

DECC

Introduction

6. Extending British Summer Time ("BST", or "GMT+1") would result in later sunrises and sunsets, when compared to a reversion to GMT during the winter months. This may affect annual and peak electricity and gas demand, and thereby carbon emissions and security of supply. This note sets out the potential effects that might be expected and the available evidence quantifying them.

7. Extending BST would be likely to lead to shifts in the pattern of demand for gas and electricity. However the extent to which this will lead to material changes in the level of annual or peak demand is not clear:

a. The impact on gas demand for space heating will depend on the extent that slightly increased demand from marginally colder mornings are offset by reduced demand from marginally warmer evenings. However the overall heat requirement remains the same suggesting that we would not expect any significant impacts on the overall level of demand.

b. There is likely to be a more significant impact on patterns of electricity demand due to potential changes to the usage of artificial lighting. The main effect would be a switch in artificial lighting demand from the evening to the morning. To the extent that the (traditional) working day would be more aligned with natural daylight, there may be an overall reduction in artificial lighting demand. A change in the pattern of electricity demand may indirectly affect the pattern of gas demand (for base- and peak-load electricity generation).

8. The following sections:

· discuss available evidence we have on the effect in the UK of extending BST on overall energy demand;

· highlight specific additional considerations for electricity and gas markets;

· note the implications for carbon budgets and renewables targets; and

· highlight other relevant considerations.

Overall energy demand

9. As outlined above one would expect overall energy demand to reduce as a result of the change, and indeed a recent study (Hill et al, 2010) [1] that considered the impact of moving the clocks forward in winter (from GMT to GMT+1) did estimate an annual saving of approximately 0.5 MtCO2e per year.

10. The analysis is based on actual half-hourly electricity data from the National Grid. The authors construct a demand profile by fitting observed weekday electricity demand to time, temperature, daylight (illumination) and baseline electricity consumption. By fitting observed data to a model, it is possible to forecast what the impact of changing the clocks (all other factors staying constant) would be on UK energy use.

11. The authors found the following:

   

· During a trial period, in 1968 – 1971, where GMT+1 was applied year round, energy consumption was reduced overall.

· The modelled results suggest that electricity savings would be observed throughout the period November to March. The emissions reduction associated with such a change is estimated at 0.45 MtCO2e per year.

12. However, there may also be complex behavioural factors that need to be considered, such as the fact that households may be more likely to turn lights on when it is dark than off when it is light. This effect could conceivably lead to an increase in energy demand as a result of the change which was found by studies commissioned by Defra from the Buildings Research Establishment (BRE) in 1990 [2] and 2006 [3] .

13. These studies are based on simulation modelling of lighting, heating and cooling in UK domestic and non-domestic building stock, rather than observations. These reports came to the somewhat counter-intuitive conclusion that moving the clocks forward by an hour would lead to an increase rather than decrease in energy consumption. This is because, in the models, lights were turned on more in the mornings (because mornings were darker) but not off later in the day, because individuals are less likely to turn lights off when it is light than they are to turn lights on when it is dark.

14. Projecting simulation results onto the UK buildings stock, the 2006 BRE study found an overall increase in energy use from extending BST of 0.9%, resulting in an increase in UK territorial emissions of 1.3 MtCO2e [4] per year. This is due to ‘perverse’ human behavioural patterns linked to an eagerness to switch lighting and heating on when needed, but less care in switching lighting and heating off when not needed

15. Most of this is driven by lighting across both sectors, whilst heating also contributes to this effect but to a lesser extent. Estimated energy use increased for non-domestic lighting by 3.6% and for domestic lighting by 1.8%. Increases in energy use for non-domestic and domestic heating were estimated at 1.2% and 0.2% respectively. The smaller magnitudes for heating are consistent with the greater within-day variation of natural light compared to temperature, and the ability of buildings to store heat.   

16. The evidence therefore suggests a mixed picture and is not strong enough to conclude either way what the impact on demand would be.

Effects on electricity markets

17. Evening peak electricity consumption may flatten (i.e. peak evening demand is shifted to the morning) as a result of extending BST during the winter months, but peaks between Great Britain and France may become more aligned, with implications for prices in situations of low generation capacity margin.

18. Hill et al’s (2010) work also examined the impact of extending BST on peak electricity demand. They found the following results:

· There is an observed measurable drop in peak electricity consumption in the spring, when the clocks go forward by one hour, and a similar jump in peak electricity consumption in the autumn when the clocks go back.

· The modelled results also show that the impact of extending BST would reduce evening peak electricity demand (and increase morning demand), with the most pronounced effect in the spring (with peak demand reduced by 4%).

19. Reductions in peak electricity consumption bring benefits for security of supply, however there are potential adverse effects associated with interconnection to France. Typically the interconnector between the UK and France may be in import or export mode depending on the relative demand/supply position and hence price signals, and can switch for each half hour period. Under current arrangements for GMT/BST, the peak periods in France and the UK are offset and there is only a limited common, overlapping period, when demand in both countries is simultaneously at peak.

20. Extending BST may affect flows through the interconnector between Great Britain ("GB") and France, in particular by aligning peaks in electricity demand between the two countries during the winter months. Loss of capacity margin in either system (caused either by large loss of capacity or severe weather events), would be expected to lead to an increase in prices due to scarcity of capacity. With the two peaks aligned, this could exacerbate the peak in GB prices in the event of French demand for GB electricity exports.

21. With greater physical integration of European markets in future this issue will grow in importance. A credible future scenario could be one with a much greater need for European wide balancing, particularly reliant on Norwegian Hydro, due to the higher level of intermittency from wind. Therefore, coincident peaks in Northern European countries could have the potential to place the system under stress.

Effects on gas markets

22. The impact on gas demand for space heating is likely to be limited, but a flattening of peak electricity consumption, could, depending on the relative fossil fuel prices, result in a fall in gas demand for electricity generation.

23. In the context of daily energy use, gas demand is driven by two distinct factors:

· indirectly through power generation to meet base and peak-load electricity demand; and

· directly through space heating in both the domestic and non-domestic sectors.

24. Reductions in peak energy demand may lead to a reduction in demand for gas. The section above highlighted that the evidence on the effect of extending BST on average electricity demand was mixed. To the extent that peak electricity demand is reduced, this may reduce the need for peaking plant. Depending on the price of gas relative to coal, gas-fired generation is sometimes used to meet peaks in electricity demand.

25. The impact on gas demand for space heating will depend on the extent that slightly increased demand from colder mornings are offset by reduced demand from slightly warmer evenings. However the overall heat requirement remains the same suggesting that we would not expect any significant impacts on the overall level of demand. 

26. In the gas market there is a need to balance the system over the course of the day rather than the half-hour, therefore shifting the demand for gas during the day without affecting the overall level of demand is unlikely to have the same consequences as for electricity in terms of security of supply.

Implications for carbon budgets

27. The effect on carbon budgets of extending BST is likely to be limited.

28. The government’s "interim" carbon budgets require a reduction in greenhouse gas emissions by at least 34% by 2020, relative to 1990 levels. These interim budgets can be met:

· through domestic effort in the sectors not covered by the EU Emissions Trading System ("EU ETS"); and

· through purchase of international credits.

29. Power generation is covered by the EU ETS, so any change in electricity demand will not contribute to achieving the UK’s carbon budgets. Peaking generation plant tends to be relatively high carbon intensity so extending BST could reduce the UK’s purchases of EUAs [1] through flattening peaks in electricity demand, especially during the "shoulder months" (November and March).

30. To the extent that annual gas demand for domestic heating is affected, there may be some effect. As discussed above in paragraphs and , this effect is likely to be limited.

Implications for renewables targets

31. To the extent that extending BST reduces energy consumption, this may reduce the cost of meeting the renewables target.

32. The EU Climate and Energy Package creates a target proportion of energy consumption which is to be delivered from renewable sources. The target follows a rising trajectory to reach 15% of capped gross final energy consumption by 2020 [1] .

33. Changes in final energy consumption in 2020 (with the exception in most cases of changes in aviation consumption [2] ) will change the absolute level of renewable energy supply that the UK is required to achieve. Reductions in energy consumption in 2020 will therefore be associated with an avoided cost of renewables. DECC/HM Treasury appraisal guidance [3] suggests that an illustrative figure for the avoided cost of renewables from reducing energy consumption by 1 MWh in 2020 would be approximately £18/MWh (in 2009 prices). However, the guidance notes that there is uncertainty around this figure.

Other considerations

34. It is important to note that neither Hill et al (2010) nor the BRE study look at the impact on emissions from transport or other sources. If a change in clocks led to changes in behaviour (the tourism industry, for example, believes changing to European time would lead people to spend more time outdoors) or economic activity, this would affect emissions.

35. Furthermore, neither paper considers the impact of the latest energy efficiency measures. In particular, the introduction of more energy efficiency lighting will drive down emissions from this source and therefore the impact (positive or negative) on lighting use will be diminished.

36. Smart meters with Time of Use ("ToU") tariffs are likely to provide a more targeted future source of changes in consumption patterns through encouraging a shift of energy demand from peak times to off-peak times. For example, in DECC’s most recent impact assessment on domestic smart metering roll-out [1] , we assume a 20% take up by consumers of the ToU tariff (in addition to the existing group using this option) and a resulting overall 3% electricity bill reduction and 5% peak use reduction for these customers.

DFT

Street Lights

37. Any extension of British Summer Time (BST) into the winter would result in the hours of darkness shifting backwards. It is expected the effect on energy usage from the operation of street lights would be minimal as the number of hours of darkness and therefore the period of time street lighting is in operation would remain the same.

38. This view is shared by officials at the Highway Agency who are responsible for the motorway and trunk road network. The Institution of Lighting Professionals likewise considers the effects on energy usage to be minimal. In addition, the mere shift in the hours of darkness should have little impact on the use of light by road vehicles, which are not powered by sustainable energy sources.

BIS

Wider Considerations.

39. A change in the time zones would need to take into consideration the potential wider implications of such a move including the regional impact for Northern Ireland and Scotland.

40. The devolved administrations have all expressed opposition to such a move mainly due to the effects that the move would have to their enjoyment of the available light.

41. The Scottish Government is against any change the current arrangement for a number of reasons. These include, safety of children travelling to school in the morning and the potential detrimental effect on rural outdoor workers and businesses. They believe there are no compelling arguments in favour of making the change so the position of being against such a move has been maintained.

42. Northern Ireland would also be opposed to such a move as this would have a significant impact on the lighting during the summer and winter months with it not getting dark during the height of summer until around midnight and it not getting light mid winter until around 10 am. Northern Ireland is much further north and west then England. Northern Ireland so this move would be felt far more here. In addition, being on a different time zone to the Republic of Ireland would cause particular problems because of the land boundary and such a move would cause difficulties with cross-border transportation and communication links.

43. Wales are aware that there are a range of opinions, however, there is no real strength of feeling to support any proposed change to the current position.


[1] The impact on energy consumption of daylight saving clock changes , Hill et al. , Energy Policy (2010)

[2] The Effects of clock change on lighting energy use , Littlefair, BRE ref 285/89 (1990)

[3] The Effect of clock changes on energy consumption in UK Buildings , Pout (2006)

[4] Note, for the purposes of carbon accounting, any change in UK territorial emissions as a result of changes in electricity demand would not represent a change in (global) emissions savings, as the UK power sector is covered by the EU Emissions Trading Scheme (“ETS”) “cap”.

[1] “EUA” stands for “European Union Allowances”, the name given to t radable emission credits under the European Union Emissions Trading Scheme.

[1] As defined in the Renewable Energy Directive, the definition of gross final energy consumption (gfec) in the target is capped by setting a maximum value on the level of aviation within gfec at 6.18% of the uncapped level of gross final energy consumption.

[2] A change in UK aviation consumption in 2020 that leaves the level of aviation consumption above 6.18% of gfec will not have any effect on the level of the renewables target. Changes that bring the level below 6.18% would reduce the target.

[3] Valuation of energy use and greenhouse gas emissions for appraisal and evaluation , DECC/HM Treasury, June 2010

[1] http://www.decc.gov.uk/assets/decc/Consultations/smart-meter-imp-prospectus/221-ia-smart-roll-out-domestic.pdf