Year 9 Science · Unit 3 · Lesson 22
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Learning Goals
1. Match each measure to what it tells you. Write the letter in the middle column.
| Measure | Letter | What it tells you |
|---|---|---|
| Total energy use | A. How much energy the economy uses to produce each dollar of wealth | |
| Energy use per person | B. A country’s overall demand for energy, and its overall impact | |
| Energy intensity | C. The energy use of an average person, which reflects lifestyle |
2. What does decoupling mean? Why is it a sign of progress?
Real-world context: Iceland
Iceland makes almost all of its electricity from hydro and geothermal power. Yet in 2023 the average person in Iceland used about 224 MWh of energy, one of the highest figures in the world. Much of Iceland’s electricity goes to aluminium smelters, attracted by abundant, comparatively low-cost electricity.
Figures: Energy Institute Statistical Review (2026).
3. Explain how a country can have 100% renewable electricity and still use a huge amount of energy per person.
4. Why does a “100% renewable electricity” figure tell only part of a country’s energy story? Name one other measure you would want to see, and say why.
5. An economist predicts that between 2025 and 2040 Australia’s GDP will grow by 50% and its energy intensity will fall by 40%. Use total energy = energy intensity × GDP to find the percentage change in Australia’s total energy use.
Change %
Data: Australia’s energy use over time
Table 1 follows Australia from 1990 to 2019.
| Year | Total energy (TWh) | Population (millions) | Energy per person (MWh) |
|---|---|---|---|
| 1990 | 1,022 | 17.1 | |
| 2009 | 1,478 | 21.8 | |
| 2019 | 1,595 | 25.5 |
Compiled by OWID from Energy Institute and UN population estimates.
6. Complete the last column of Table 1, to one decimal place. Show one of your calculations here.
7. Between 2009 and 2019, by what percentage did (a) Australia’s total energy use and (b) its energy use per person change? Give each to the nearest whole number, and explain what the two results show together.
(a) Total %
(b) Per person %
Scenario: planning for 2050
Over the past decade, the amount of electricity that NSW households and businesses take from the network has hardly changed, largely because rooftop PV on houses now covers much of their midday use. A council planner extends the past trend as a straight line and says: “Demand isn’t growing, so NSW needs no new power stations or transmission lines before 2050.”
8. Evaluate the planner’s prediction. Explain why extending a past trend can mislead, how electrification could change the demand for grid electricity, and what a better prediction would include.