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?