Enter Project Inputs
The input area uses 3 columns on large screens, 2 on medium screens, and 1 on mobile screens.
Example Data Table
| Input Item | Example Value | Explanation |
|---|---|---|
| Number of Fixtures | 120 | Total luminaires considered in the retrofit. |
| Current Wattage | 72 W | Existing fluorescent or legacy fixture load. |
| LED Wattage | 28 W | Nominal LED fixture wattage before controls. |
| Dimming Reduction | 10% | Expected controls benefit from dimming or occupancy strategies. |
| Hours / Day | 10 | Average daily operating schedule. |
| Days / Month | 26 | Monthly usage frequency. |
| Electricity Rate | $0.14/kWh | Blended energy tariff. |
| Net Project Cost | Calculated | Fixture cost plus installation minus rebates. |
Formula Used
1) Effective LED wattage
Effective LED Wattage = LED Wattage × (1 − Dimming Percentage ÷ 100)
2) Annual energy use
Annual kWh = (Fixture Count × Wattage × Hours per Day × Days per Month × 12) ÷ 1000
3) Annual energy cost
Annual Energy Cost = Annual kWh × Electricity Rate
4) Annual demand cost
Annual Demand Cost = Connected kW × Coincidence Factor × Demand Charge Rate × 12
5) Annual maintenance cost
Annual Maintenance = Fixture Count × Maintenance Cost per Fixture per Year
6) Annual replacement cost
Annual Replacement = Fixture Count × (Annual Operating Hours ÷ Lifespan Hours) × Replacement Cost per Fixture
7) Annual operating cost
Operating Cost = Energy Cost + Demand Cost + Maintenance + Replacement
8) Annual savings
Annual Savings = Current Annual Operating Cost − LED Annual Operating Cost
9) Project net cost
Project Net Cost = Fixture Count × (LED Unit Cost + Installation Cost − Rebate per Fixture)
10) Simple payback
Simple Payback (months) = Project Net Cost ÷ Monthly Savings
11) NPV
NPV = −Project Net Cost + Σ [Annual Savings ÷ (1 + Discount Rate)t]
12) CO₂ reduction
Annual CO₂ Reduction = Annual kWh Saved × Emission Factor
How to Use This Calculator
- Enter the total number of fixtures in the lighting project.
- Provide the existing fixture wattage and proposed LED wattage.
- Enter the expected controls reduction, if dimming or sensors apply.
- Add operating hours, days per month, and your electricity rate.
- Enter demand charges if your utility bill includes them.
- Fill in equipment cost, installation cost, rebates, and maintenance values.
- Provide replacement costs, lifespans, discount rate, and analysis period.
- Press Calculate LED Lighting Cost to view results above the form.
- Use the CSV and PDF buttons to export the result summary.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates energy use, operating cost, maintenance, replacement expense, annual savings, payback, ROI, NPV, and emissions reduction for an LED retrofit project.
2) Why include demand charges?
Some utility tariffs bill both energy consumption and peak demand. Lower lighting wattage can reduce connected demand and improve total project savings.
3) What is the dimming or controls reduction field?
It models extra savings from occupancy sensors, daylight harvesting, scheduling, or dimming controls. The percentage lowers effective LED wattage during operation.
4) How is replacement cost estimated?
The calculator spreads replacement cost across yearly operating hours using the fixture lifespan. Shorter lifespan products produce higher annualized replacement expense.
5) What does NPV mean here?
NPV discounts future savings into present value. A positive NPV suggests the LED project creates financial value over the chosen analysis period.
6) Can I use blended electricity pricing?
Yes. A blended rate is practical when your bill combines several charges into an effective average cost per kilowatt-hour.
7) What if monthly savings are negative?
Negative savings usually mean the proposed LED scenario is not cost-effective under the entered assumptions. Review wattage, operating hours, rates, and project cost.
8) Is this suitable for commercial projects?
Yes. It is especially useful for offices, retail spaces, schools, warehouses, and other facilities comparing legacy fixtures against LED upgrades.