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whether it's a weekday or the weekend.
Generally, demand rises during the week, when factories and offices are operational, and then
decreases when a lot of them close at the end of the week. So demand falls at the weekend. Those
are variations that take place within a given week. During any given day, there are factors such
as mealtimes, when electric ovens are switched on - obviously, that causes a jump in
consumption. Even commercial breaks during popular TV shows can cause blips in demand.
There can be a sudden rise when people rush to switch kettles on, or heat up snacks in
microwaves, and then a sudden fall shortly afterwards.

c Complete the following extracts from the talk using the correct form of the words in the
box.
decrease; fall; increase; rise;
1 During periods of very cold or very hot weather, demand increases .
The in demand is obviously due to millions of electric radiators
coming on ...
2 ... a key factor which or demand, is
whether or not it’s light or dark ...
3 ...on cold, dark, winter evenings, the in demand is significant...
4 Generally, demand during the week, when factories and offices are
operational...
5 So demand at the weekend.
6 There can be a sudden when people rush to switch kettles on, or
heat up snacks in microwaves, and then a sudden shortly afterwards.

d 8.6 Read the next part of Helen’s talk and answer the following questions.
1 Why does the company often have significant spare generating capacity?
2 What ideal situation does Helen describe?
3 Why is this ideal situation difficult to achieve?

Helen: Because electricity consumption fluctuates across a significant range, in order to cope
with peak demand our maximum capacity is equivalent to the top of that band of fluctuation.
That means that during off-peak periods, we have significant spare generating capacity. Now, in
an ideal world, it would be good to use that spare capacity to generate power and store it for use
during peak times. Unfortunately, as you probably know, electrical charge is extremely difficult
to store in large amounts - you can't just charge up huge batteries. So we use an innovative
technique to store up power potential during off-peak periods.

e Match the words (1 -8) from the talk to the definitions (a-h).
1 continuous a maximum power requirement at a given time
2 fluctuations b amount between an upper and lower limit
3 peaks and troughs c without interruption
4 peak demand d high points and low points on a graph curve
5 range e regular and repetitive
6 band of fluctuation f momentary rises followed by a fall
7 blips g changes, movements in general
8 continual h zone of up-and-down movement

f Look at the graph showing electricity demand fluctuations over a week in the UK. Find
parts or patterns on the graph described by the words in Exercise 8e and analyse the
fluctuations. How do they compare with Helen’s explanation?

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