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Tuesday, 16 May 2017

Which Appliances are Best to Time-shift?


It is sometimes said that there is not enough energy consumed by wet appliances to eliminate 7GW of peak consumption by time-shifting them alone. I leave you to judge.

The trend of wet appliances’ consumption has been inexorably upwards, and is now second only to consumer electronics. Much of the increase is due to an undesirable increase in the use of tumble dryers, but I am not here to preach austerity. If you live in a flat or gardenless house, it may be the only realistic option.

Reading off the above graph, we have a Mtoe figure for each appliance type:

APPLIANCE TYPE
Mtoe 2014
GWh (Mtoe x 11,630)
PERCENT OF TOTAL
Light
1.0
11,630
14.2
Cold
1.1
12,793
15.7
Wet
1.3
15,119
18.5
Consumer Electronics
1.8
20,934
25.7
Home Computing
0.6
6,978
8.5
Cooking
1.2
13,956
17.1
TOTAL
7.0
81,410
100

There are around 80 winter days when it is desirable to reduce peak consumption by up to 7GW and by around  18GWh spread over the 5 hours of the peak, so by a total of 80x18=1440 GWh/year. This is 1.7% of total annual domestic consumption, and 9.5% of total annual wet consumption.

There are of course other candidates for time-shifted consumption as well as wet appliances.  Cold devices (mainly fridges and freezers in UK) and increasingly home computing (laptops, smartphones and tablets all have batteries) are if anything even less time-sensitive in direct grid consumption than wet appliances, and are now already 24% of the total vs wet appliances 18.5%. 

The reason we are not focussing on them is the relatively low consumption per device. A typical house may have three wet appliances and ten or more cold and computing ones.

Would you rather go for the wet or the cold and computing!

 It’s up to you. Both is best!