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Calculators / Science / Lighting energy savings
Lighting energy savings calculator
Compare annual energy and cost before and after a lighting upgrade.
On this page
Annual energy saved2,400kWh
Annual cost saved480
Power reduction1,000W
Calculator controls
How to calculate
Compare annual energy and cost before and after a lighting upgrade.
annual savings = watt reduction × quantity × daily hours × days ÷ 1000
Worked example
Old lamp power each (W): 60; New lamp power each (W): 10; Number of lamps: 20; Hours used / day: 8; Days used / year: 300; Electricity price per kWh: 0.2.
Annual energy saved: 2,400 kWh; Annual cost saved: 480 ; Power reduction: 1,000 W.
Assumptions and limits
Rated watts do not capture maintenance, controls, cooling interaction, light output, power quality, or changing tariffs.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Compare annual energy and cost before and after a lighting upgrade. Every assumption remains visible so the result can be checked or changed.
When this tool is useful
Use the lighting energy savings for an initial estimate, comparison, or classroom calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Old lamp power each (W) | Enter a number of at least 0 and no more than 1000000000000. |
| New lamp power each (W) | Enter a number of at least 0 and no more than 1000000000000. |
| Number of lamps | Enter a number of at least 1 and no more than 100000. |
| Hours used / day | Enter a number of at least 0 and no more than 24. |
| Days used / year | Enter a number of at least 0 and no more than 366. |
| Electricity price per kWh | Enter a number of at least 0 and no more than 1000000000000. |
Frequently asked questions
What are the limits of this lighting energy savings?
Rated watts do not capture maintenance, controls, cooling interaction, light output, power quality, or changing tariffs.
Can I use different units?
Use the units printed beside each field. Convert measurements first when your source uses different units.