E NE RG Y MAT TER S
FACT SHEET 5: BENCHMARKING
What is benchmarking?
When setting out to improve the energy
efficiency of your home or business, it
would be handy if you had some idea of
how you were going as you made changes.
Hence, you keep track of your energy
consumption by checking your electricity
and gas bills as they come in (see Fact
Sheet: Understanding You Electricity
Bill).
This is one type of benchmarking,
which refers to a point of reference (a
standard) which you can compare to, as a
way of assessing your progress.
Another type of benchmarking
compares your situation against similar
activities or facilities, particularly those
known to be doing something (eg energy
efficiency) well. It allows you to have a
target to aim at.
It also tells you how far you can
probably improve, since if you find that
your energy consumption is very close to
the benchmark house, you may not
achieve much in the way of savings.
Exercise 1
Can you see any problems with using
someone else’s house as a benchmark for
your energy reduction program?
Energy rating schemes
As you probably know, whitegoods, such
as washing machines and fridges, have a
star rating for their energy efficiency (see
Fact Sheet: The Star Rating for
Appliances). The same sort of idea is also
applied to buildings, large and small.
Some planning authorities (eg state and
local governments) are starting to use
these systems as part of the approval
process for new buildings and renovations.
Generally, the process for calculating
the star rating is quite complex, requiring
expensive software and beyond the ability
of a normal householder.
Australian examples of these systems
include the Building Sustainability Index
(BASIX - New South Wales) and the
Nationwide House Energy Rating Scheme
(NatHERS - national).
Overseas, a simpler (and therefore
less powerful) measure called the Energy
Use Index (EUI) is used. It is the amount
of energy consumed over one year per unit
area of a building
It can be used to compare energy
consumption to similar building types or if
a particular building is renovated.
How to calculate the EUI
1.
Multiply the total kWhr of electricity
for the year, based on the power
bills, by 3.6.
2.
If gas is used, and the units are in
MJ, then leave as is. If the units are
different, find the conversion factor
to convert to MJ.
3.
Add the two energy quantities (in
MJ) together).
4.
Divide the total MJ by the floor area
of the building in square metres.
This is the EUI.
Small simple building types, such as
houses, schools and shopfront-type offices
typically would score around 750 (on
average), while more energy-intensive
commercial/service facilities such as
supermarkets or hospitals would score
above 2000. Obviously the lower the
better, but climatic factors complicate this
further.
Exercise 2
Calculate the EUI for a house with the
following energy use:
•
the floor area is 115 m2
•
electricity per quarter: 2342, 2210,
2178, 2562 kWhr
•
gas per quarter : 8710, 8924, 9012,
8634 MJ
How does its EUI compare to typical
house values?