Lighting Energy Savings Calculator
Enter existing and replacement fixture wattage, quantity, operating schedule, electricity rate, and optional project cost for a transparent retrofit estimate.
- Existing annual energy
- kWh/year
- Replacement annual energy
- kWh/year
- Annual energy saved
- kWh/year
- Annual cost saved
- $/year
- Simple payback
- years
Calculation details
- Calculation basis
- Energy boundary
Recent results
Formulas
- Existing annual kWh = existing watts x fixture count x hours/day x days/year / 1000
- Replacement annual kWh = replacement watts x fixture count x hours/day x days/year / 1000
- Annual kWh saved = existing annual kWh - replacement annual kWh
- Annual cost saved = annual kWh saved x electricity rate
- Simple payback years = project cost / annual cost saved when annual cost saved is greater than zero
Use this calculator
Estimate annual kWh and electricity-cost savings from replacing existing fixtures with lower-wattage fixtures.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This lighting energy-savings estimate uses entered wattage, schedule, and electricity-rate assumptions. It does not model light levels, controls, maintenance, demand charges, taxes, rebates, HVAC interaction, utility tariffs, or project approval.
FAQs
Does lower wattage prove the replacement is better?
No. Compare light output, distribution, color, controls, maintenance, lifetime, compatibility, heat, project cost, and applicable energy requirements in addition to wattage.
Does the payback include rebates or demand charges?
No. The simple payback uses only the entered project cost and annual energy-cost savings. Utility tariffs, rebates, taxes, demand charges, and maintenance changes need separate review.