Engineering
Lighting Retrofit Savings Calculator
Estimate retrofit kWh, operating cost, baseline reduction, annual savings, and simple payback.
Existing annual lighting energy-
Retrofit energy before controls-
Retrofit annual energy after controls-
Annual energy reduction-
Annual electricity savings-
Energy plus maintenance savings-
Simple payback-
Average monthly energy reduction-
Average monthly retrofit energy-
Decision view
Baseline and retrofit lighting floor
Baseline and retrofit lighting floorFixture rows, control zones, monthly energy reduction, annual savings, and payback share one plan.
Lighting baseline, retrofit savings, and paybackExisting annual energy is compared with retrofit monthly energy while energy reduction, annual cost savings, installed cost, and payback remain explicit.
Exact scenario comparisonRetrofit watts per fixture changes while all other entered assumptions remain constant.
| Retrofit watts per fixture | Existing annual lighting energy | Retrofit energy before controls | Retrofit annual energy after controls | Annual energy reduction | Annual electricity savings | Energy plus maintenance savings | Simple payback | Average monthly energy reduction | Average monthly retrofit energy |
|---|
Period-by-period detail
lighting retrofit monthly operating projection
How to use Lighting Retrofit Savings Calculator
- Inventory fixture count and true input watts.
- Use schedule and control factors by space type.
- Check light levels, glare, color quality, emergency lighting, and installation cost.
Calculator guide
Understanding Lighting Retrofit Savings Calculator
Lighting-retrofit savings depend on fixture watts, quantity, operating hours, controls, ballast or driver loss, tariff, maintenance, and installed cost.
Calculation method
How the calculation works
Calculate baseline and retrofit fixture energy separately, apply the entered control reduction only to retrofit energy, and combine verified maintenance savings for simple payback. Multiply connected kW by operating hours, days, and effective load factor, then compare with the entered baseline and tariff.
Lighting floor
Replace fixture rows and compare lit hours
The ceiling plan contrasts baseline and retrofit fixtures, control zones, monthly kWh, savings, and payback.
Worked situations
Practical examples
- Occupancy sensors save little in continuously occupied areas.
- LED input watts may differ from lamp label watts.
- Reduced heat can also lower cooling load but raise heating load.
Better inputs
Useful tips
- Measure representative circuits.
- Model controls separately from lamp replacement.
- Include maintenance and disposal savings outside the simple energy result.
Before relying on the result
Limitations and common mistakes
- One blended power, schedule, and tariff are used.
- Daylight, controls, demand charges, HVAC interaction, degradation, and maintenance are simplified.
- Photometric adequacy is not evaluated.
Reference
Key terms
- Connected load
- Total rated electrical input of installed fixtures.
- Control factor
- Share of scheduled time lighting is actually energized.
- Efficacy
- Light output per watt.
Important note
Calculated from the entered values using the displayed engineering relationship. Confirm design values, load cases, safety factors, standards, and field conditions with a qualified professional.
Frequently asked questions
Should fixture quantity be included in rated power?
Yes; enter the total connected kW or calculate it first.
Does the result include maintenance savings?
No, unless incorporated separately.
Does lower wattage prove equal light?
No.