# A electric storage heater uses electrical energy to heat up special bricks overnight, when electricity is cheaper. During the day, the stored thermal energy is released slowly to warm a room. Explain why the efficiency of the storage heater can never reach 100%, and describe TWO ways in which the efficiency of the storage heater could be increased.

> Edexcel A-Level Physics (9PH0) — 3.2 EMF, resistance and circuits · Explain · 5 marks

> An electric storage heater is rated at 3 kW. Over one night it stores energy in its internal bricks. During the day, some of this energy is released as useful heat into the room, but some energy is lost to the surroundings through the outer casing of the heater.

## Mark scheme (5 marks)

1. Energy cannot be created or destroyed (conservation of energy), so waste energy transfers mean useful output is always less than total input
2. Some energy is transferred as waste heat to the surroundings through the outer casing (waste energy transfer), reducing useful output
3. Thermal insulation applied to the outer casing of the heater would reduce heat loss to the surroundings
4. Correct explanation of how thermal insulation increases efficiency — less energy is wasted / a greater proportion of the stored energy is released as useful heat into the room
5. Recycling / recovering the waste heat that escapes through the casing and redirecting it into the room as useful energy input, increasing efficiency

## Key terms

- [efficiency](https://www.gradenine.co.uk/glossary/efficiency)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-electric-storage-heater-uses-electrical-732a74d9) · Published by Druglandscape Ltd.