Band 7.5 IELTS Writing Task 1 Model Answer

Overall Band Score: 7.5 · Cambridge IELTS 14 · 2026-09-22

IELTS Writing Task 1 question

The diagram below shows how electricity is generated in a hydroelectric power station.

Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

Student answer (Band 7.5)

The diagram illustrates the process by which electricity is generated in a hydroelectric power station.

Overall, the system operates in two main phases: during the day, water stored in a high-level reservoir is released to generate electricity, while at night, the flow is reversed and water is pumped back into the upper reservoir for reuse.

During the daytime, water from the river is retained behind a dam, forming a high-level reservoir. The intake gate is opened, allowing water to flow downhill through a large pipe towards the power station. As the water passes through the turbines, their blades are driven by the force of the flowing water. The turbines are connected to a generator, which converts this mechanical energy into electrical energy. The electricity is then transmitted through power lines to the national grid.

At night, when electricity demand is lower, the intake gate is closed and the direction of water flow is reversed. Water collected in the lower reservoir is pumped back through the turbines towards the high-level reservoir. In this process, the turbines operate in the opposite direction and function as pumps, returning the water to the upper reservoir. Consequently, the stored water can be used again to generate electricity during the following day.

Overall, the hydroelectric station forms a closed-loop system, in which water is repeatedly transferred between the upper and lower reservoirs to produce electricity during periods of demand.

AI examiner evaluation

Task Achievement / Task Response — Band 7.5

The student has fully addressed all parts of the task by accurately summarising the main features of the hydroelectric power station process. The response successfully covers both operational modes, distinguishing between the daytime electricity generation phase and the night-time water pumping phase. An effective overview is provided in both the second paragraph and the conclusion, capturing the dual-phase closed-loop nature of the system. Key stages such as the high-level reservoir, dam, intake gates, reversible turbines, generator, and low-level reservoir are clearly identified and sequenced without any misinterpretation of the visual data. The progression of water flow during both day and night is accurately reported. All descriptors for Band 8.0 are comprehensively met.

Coherence and Cohesion — Band 7.5

The response is logically organized with a clear overall progression from introduction to overview, daytime operations, night-time operations, and a final summary. Paragraphing is used appropriately and effectively, separating the distinct phases of the process. Cohesive devices such as 'During the daytime', 'As the water passes', 'At night', and 'Consequently' are managed well to guide the reader through the sequence. Reference words are handled accurately, ensuring the relationships between reservoirs, turbines, and the national grid remain clear throughout. The cohesion is natural and unobtrusive, supporting a smooth flow of information from start to finish.

Lexical Resource — Band 7.5

The vocabulary used is precise and well-suited to an academic process description. The student demonstrates a wide and flexible range of lexical items, incorporating less common terminology naturally, such as 'retained behind a dam', 'mechanical energy into electrical energy', 'demand is lower', and 'closed-loop system'. Word choices and collocations are accurate throughout the response. Spelling and word formation are entirely error-free, reflecting a strong command of appropriate academic register. While it stops just short of the absolute effortless sophistication of a Band 9, it easily meets the high standards of Band 8.

Grammatical Range and Accuracy — Band 7.5

The student exhibits a wide range of complex grammatical structures executed with a high degree of accuracy. Sentences such as 'As the water passes through the turbines, their blades are driven by the force of the flowing water' and 'Water collected in the lower reservoir is pumped back through the turbines towards the high-level reservoir' demonstrate excellent control over subordinate clauses and passive voice constructions. The vast majority of sentences are completely error-free, with only rare, non-systematic slips. Punctuation is used correctly throughout to separate clauses and structure the technical explanations clearly.

See this exact question answered at other band scores — the same prompt compared across bands.

Browse more IELTS Writing model answers or get your own writing scored by the same AI examiner.