Compare options that provide the same service
See this course’s project requirements
A desk-based household energy comparison with checked kWh estimates, usage assumptions and a safe no-installation conservation recommendation.
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What to include
- Calculate power-time energy with explicit units.
- Complete a quantity-aware 30-day device table.
- Separate ratings, measurements and standardized estimates.
- Compare matched lighting output and calculate differences.
- Recommend an existing-control action preserving essential services.
- Recalculate the final comparison and retain evidence limits.
Review and revise
Use these criteria to check your work and choose what to improve.
- Method: applies the course-specific rules to the supplied cases with visible intermediate work.
- Accuracy: results agree with the stated facts, units, boundaries and independent checks.
- Reasoning: explains why the result follows and identifies a limitation or unresolved question.
- Transfer: completes changed cases and revises the final project when a relevant assumption changes.
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The idea in everyday life
Fictional lamp cards: A—800 lumens, 60 W; B—800 lumens, 12 W; C—300 lumens, 5 W. Task requires 800 lumens from one compatible lamp, 5 h/day for 30 days. Compatibility and suitable light appearance are supplied for A and B; no installation is performed.
Efficiency comparisons need a comparable useful service. For lighting, lumens describe light output while watts describe power; color appearance and suitability also matter. Compare energy only after matching the task’s brightness, duration and number of lamps. A lower-power option that supplies too little light is not an equal-service comparison.
Compare options that provide the same service — worked practice
Efficiency comparisons need a comparable useful service. For lighting, lumens describe light output while watts describe power; color appearance and suitability also matter. Compare energy only after matching the task’s brightness, duration and number of lamps. A lower-power option that supplies too little light is not an equal-service comparison.
Fictional lamp cards: A—800 lumens, 60 W; B—800 lumens, 12 W; C—300 lumens, 5 W. Task requires 800 lumens from one compatible lamp, 5 h/day for 30 days. Compatibility and suitable light appearance are supplied for A and B; no installation is performed.
1. 1. Match
Identify the cards satisfying the stated output.
You should see: A and B supply 800 lumens; C does not.
2. 2. Calculate
Find energy for the two matching cards.
You should see: A: 9 kWh; B: 1.8 kWh.
3. 3. Compare
Calculate energy difference and fraction of A avoided.
You should see: 9−1.8=7.2 kWh; 7.2÷9=80%.
4. 4. Qualify
Explain why C is not ranked as equivalent service.
You should see: Its 300 lumens fail this task even though watts are lower.
What to finish
An equal-service comparison with kWh difference, percentage and an excluded nonmatching card.
Watch for this
B uses 0.012 kW×5 h/day×30 days=1.8 kWh. Keep the daily duration and full period in the calculation.
How can I tell I understand it?
Estimate a changed matching-power option without treating watts as brightness.
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Source & access notes · checked 2026-10-01
Web open/search showed the official page, its topic heading and relevant concept description. This is a content/source check, not a provider endorsement.
Access: Official page retrieved with the web reader on 2026-10-01; interactive tools and videos were not certified by retrieval.
Reuse: Original fictional teaching cases, calculations, questions and examples; link and short factual paraphrase only. No copied source exercises or illustrations.
Source & access notes · checked 2026-10-01
Web open/search showed the official page, its topic heading and relevant concept description. This is a content/source check, not a provider endorsement.
Access: Official page retrieved with the web reader on 2026-10-01; interactive tools and videos were not certified by retrieval.
Reuse: Original fictional teaching cases, calculations, questions and examples; link and short factual paraphrase only. No copied source exercises or illustrations.
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