Energy conservation and efficiencyin buildings 279unnecessary use of lighting reduces the overall efficiency to perhaps
no more than one per cent.^9 Assessments have been carried out across
all energy uses comparing actual energy use with that which would be
consumed by ideal devices providing the same services. Although there
is some difficulty in defining precisely the performance of such ‘ideal’
devices (see box below for a discussion of thermodynamic efficiencies),
assessments of this kind come up with world average end-use energy
efficiencies of the order of three per cent. That sort of figure suggests
that there is a large amount of room for improvement in energy efficiency,
perhaps by at least threefold.^10 In this section we look at the possibilities
for energy saving in buildings; in later sections we shall consider possible
savings in transport and in industry.^11
To be comfortable in buildings we heat them in winter and cool them
in summer. In the United States, for instance, about thirty-six per cent
Efficiency of appliances
There islarge potential for reducing theelectricity consumption from
appliances used in domestic or commercial buildings. If, in replacing
appliances, everyone bought the most efficient available, their total elec-
tricity consumption could easily drop by more than half.
Take lighting for instance. One-fifth of all electricity used in the USA
goes directly into lighting. This can easily be reduced by the wider use of
compact fluorescent light bulbs that are as bright as ordinary light bulbs,
but use a quarter of the electricity and last eight times as long before
they have to be replaced – with significant economic savings to the user.
For instance, a 20-W compact fluorescent bulb (equivalent to a 100-W
ordinary incandescent light bulb) costing £5 or less will use about £20
worth of electricity over its lifetime of twelve years. To cover the same
period eight ordinary bulbs would be needed costing about £4 but using
£100 worth of electricity. The net saving is therefore about £80. A further
large increase in the efficiency of lighting will occur when light emitting
diodes (LEDs) giving out white light become commonplace.^14 The latest
such device that is about one square centimetre in size and consuming
only 3-W, produces the same light as a 60-W incandescent bulb.
The average daily electricity use from the appliances in a home
(cooker, washing machine, dishwasher, refrigerator, freezer, TVs, light-
ing) for typical appliances bought in the early 1990s amounts to about
10 kWh per day. If these were replaced by the most efficient available
now, electricity use would fall by about two-thirds. The extra cost of
the purchase of efficient appliances would soon be recovered in the sav-
ings in running cost. Similar calculations can be carried out for other
appliances.