Quick guide
How to use this calculator
- Enter values from one real situation and keep currencies, quantities, and periods consistent.
- Use the optional fields only when they apply; the calculator will keep every entered adjustment visible in the result.
- Compare the component outputs and read the calculator-specific boundary before making a purchase or plan.
Calculation method
Calculation method
Energy = fixtures × watts × hours ÷ 1,000; lamp purchases = fixtures × ceiling(hours used per fixture ÷ rated lamp life).
Entered fixed decimals use exact rational arithmetic wherever the task involves money, ratios, or allocations. Whole packages, tables, seats, and items round only where the real task requires indivisible units.
Worked example
Worked example
Ten 60 W lamps replaced by 9 W lamps used 3 hours daily save about 558.45 kWh annually.
Energy = fixtures × watts × hours ÷ 1,000; lamp purchases = fixtures × ceiling(hours used per fixture ÷ rated lamp life).
Supported inputs
Precision and limits
Your scenario
No live price, promotion, retailer policy, tax, cultural norm, household consumption rate, attendance rate, or media speed is supplied automatically.
Plan, not a guarantee
Results organize visitor-entered assumptions. They do not guarantee availability, attendance, product life, savings, suitability, or contractual rights.
Precision and privacy
Inputs stay in this browser. Invalid denominators, contradictory counts, impossible percentages, and unsupported ranges return explicit messages rather than misleading results.
Calculator-specific boundary
Lamp purchases assume every fixture starts the comparison horizon with a newly purchased lamp. Rated life and wattage do not guarantee real service life, compatibility, light output, dimmer performance, colour quality, fixture temperature, or installation suitability.
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