A fair comparison judges every energy source on the same criteria, then says which one suits a stated need. This lesson shows how to build that answer from a table.
This lesson is part of natural resources and energy choices. If you still mix up resource types, start with classifying resources using a renewal timescale.
What makes a comparison fair?
Each source must be measured against the same criteria. If you judge solar on cost and diesel on noise, you are describing two different things, not comparing.
Start by writing the criteria in a row. Then fill in each source against every criterion, leaving a blank where the data is missing.
Worked example: powering a small island
The numbers here are made up for illustration. A school on a small island needs electricity. Two options are supplied.
| Criterion | Solar panels with batteries | Diesel generator |
|---|---|---|
| Set-up cost | RM180 000 | RM60 000 |
| Yearly running cost | RM4 000 | RM30 000 |
| Works at night without extra parts | No, needs batteries | Yes |
| Carbon dioxide released | None while running | Released every hour of use |
| Fuel delivery needed | No | Yes, by boat |
First, calculate the cost over 10 years. Solar is RM180 000 + (10 × RM4 000) = RM220 000. Diesel is RM60 000 + (10 × RM30 000) = RM360 000.
So over 10 years, solar costs RM140 000 less, even though it costs RM120 000 more to set up. Solar saves RM26 000 a year on running costs (RM30 000 − RM4 000). It needs 120 000 ÷ 26 000, about 4.6 years, to win back its extra set-up cost, so it pulls ahead during year 5.
Now write the comparison in one sentence: “Solar costs RM120 000 more to install, whereas diesel costs RM26 000 more to run each year, so solar becomes cheaper overall from the fifth year.”
The mistake that loses marks
A weak answer writes two paragraphs. One says solar is clean and expensive to install. The other says diesel is cheap to install and pollutes.
Each statement is true, but the marker cannot see a link between them. The fix is one sentence per criterion, with both sources inside it.
| Weak (describing) | Strong (comparing) |
|---|---|
| Solar has no fuel cost. Diesel needs fuel. | Solar needs no fuel delivery, whereas diesel depends on boat deliveries. |
| Diesel is cheaper to set up. | Diesel costs RM60 000 to set up, which is RM120 000 less than solar. |
How do I reach a conclusion?
Name the purpose first, then the deciding criteria. For this school, the purpose is reliable power for ten years with few deliveries.
A supported conclusion might read: “For a school that needs power every day, solar with batteries is the better choice on cost and fuel supply. The table does not say how long the batteries last, so the saving may be smaller if they need early replacement.”
The last sentence earns marks because it names the missing evidence, which shows you read the table carefully. The graph evidence and fair-comparison lab helps you set out criteria before you write.
Check yourself
A village chooses between a small hydro turbine and a petrol generator. The hydro turbine costs RM90 000 to set up and RM2 000 a year to run. The petrol generator costs RM25 000 to set up and RM18 000 a year to run. Compare their cost over 5 years.
Answer
Hydro over 5 years: RM90 000 + (5 × RM2 000) = RM100 000.
Petrol over 5 years: RM25 000 + (5 × RM18 000) = RM115 000.
A comparison sentence: “Hydro costs RM65 000 more to set up, whereas petrol costs RM16 000 more to run each year, so over 5 years hydro is RM15 000 cheaper.” The data does not say whether the stream flows all year, so reliability cannot be compared.
What to study next
Next, practise separating supply data from use data in distinguishing resource extraction from consumption data. Then test the whole cluster with the natural resources practice set.
To have a teacher check your comparison paragraphs line by line, see online one-to-one Geography tuition.