Lighting Retrofit ROI: How to Calculate Savings and Payback
Updated: 3 days ago
Lighting retrofit ROI starts with two defensible figures: the complete project cost and the annual savings the project is expected to produce. Record how each figure was calculated, then distinguish simple payback from return over a stated period.
This guide uses a transparent commercial LED example. The figures are illustrative assumptions, not a customer case study, a market price or a promised result.
The inputs you need before calculating payback
Collect the following for each fixture group or area:
Existing and proposed fixture quantities.
Complete system input watts, including the existing ballast where applicable.
Annual operating hours and any existing control effects.
The applicable electricity tariff and avoidable energy charges.
Materials, labor, access equipment, disposal and other installed costs.
Estimated rebates, their approval status and expected payment timing.
Documented maintenance costs if maintenance savings will be included.
Use the lighting audit checklist to collect the baseline. The LED retrofit savings calculator can help test project assumptions before they enter the proposal.
Step 1: Calculate existing and proposed energy separately
For a constant-power fixture group, annual energy equals quantity multiplied by input watts and annual operating hours, divided by 1,000.
Illustrative assumptions: 100 existing fixtures at 59 W each, replaced by 100 LED fixtures at 30 W each. Both cases operate for 4,000 hours per year. The avoided energy rate is US$0.15/kWh. Controls, demand charges, maintenance and HVAC effects are excluded from this first calculation.
Calculation | Existing | Proposed LED |
|---|---|---|
Connected lighting load | 5.9 kW | 3.0 kW |
Annual energy | 23,600 kWh | 12,000 kWh |
Annual energy cost | US$3,540 | US$1,800 |
Annual energy savings are 11,600 kWh, worth US$1,740 per year under these assumptions.
The 59 W baseline is an example input, not a universal rating for every two-lamp T8 fixture. Verify the installed system. If the upgrade changes fixture counts or operating hours, use the different quantities and schedules in their respective cases.
Step 2: Establish gross and net installed cost
Include the work required to deliver the agreed scope: products, accessories, installation, mobilization, lift rental, disposal, controls commissioning, permits and applicable project costs. State whether tax is included and use the same currency throughout.
For this example, assume a US$12,000 installed price and a US$2,000 estimated rebate. Estimated net cost is US$10,000 if the incentive is approved and received.
A rebate does not always reduce the amount due at installation. Show cash due and expected later reimbursement separately where appropriate. The rebate cash-flow guide explains that distinction.
Step 3: Calculate simple payback
Simple payback, years = net project cost ÷ annual net savings.
Using energy savings alone, the example produces:
Before the estimated rebate: US$12,000 ÷ US$1,740 = 6.90 years.
After the estimated rebate: US$10,000 ÷ US$1,740 = 5.75 years.
Simple payback does not account for the time value of money, financing, future replacements or savings after the payback point. It is a useful screening measure when its limits and assumptions are clear.
Step 4: Define what you mean by ROI
State the period and formula instead of presenting an unexplained ROI percentage.
One simple, undiscounted project-return calculation is:
Return over the stated period = (cumulative net operating savings − net initial cost) ÷ net initial cost × 100%.
At a constant US$1,740 per year for ten years, cumulative savings would be US$17,400. Against the assumed US$10,000 net initial cost, that gives a 74% undiscounted ten-year return. This simplified example excludes maintenance, replacements, tax, financing, changing rates and discounting. It is not an internal rate of return.
For decisions involving different lifetimes, replacement schedules or financing structures, use an appropriate life-cycle analysis. DOE's Building Life Cycle Cost resources explain tools for evaluating initial and future building costs.
Add controls savings to the remaining LED consumption
Calculate the LED-only case first, then apply an evidenced control assumption to the energy that remains. Existing controls, overlapping strategies and minimum dimmed output all affect the result.
In the example, a hypothetical 20% reduction in the LED-only 12,000 kWh would save another 2,400 kWh, or US$360 per year. The 20% is a scenario input, not an expected result for every building. The cost of the controls must also be added before comparing payback.
Record occupancy patterns, schedules and commissioning requirements. Our commercial lighting controls guide covers the scope questions to resolve before quoting.
Treat demand, maintenance and HVAC effects separately
Connected-load reduction does not automatically equal billed demand savings. Include demand savings only when the tariff, timing and billing method support the calculation. Fixed charges may remain unchanged.
For maintenance, use an observed replacement history, product costs, labor and access requirements. Longer rated life alone does not establish a fixed annual saving. Include realistic LED driver, sensor or fixture replacement costs where they are material to the study.
HVAC effects depend on climate, heating and cooling systems, schedules and system interactions. A reduced lighting load can lower cooling demand but increase heating needs. Do not add a generic HVAC savings percentage to every project.
Show assumptions beside the proposal results
Present annual kWh savings, estimated annual cost savings, gross price, incentive status, estimated net cost and simple payback together. Add the wattages, hours, rates and excluded effects that let the customer check the figures.
Distinguish a forecast from verified performance. DOE's measurement and verification guidance explains the role of a documented baseline and post-installation verification.
LumaQuote connects recorded lighting quantities with proposed replacements, costs, rebates and proposal output. Inspect a sample lighting retrofit proposal and check current plans to test your own project assumptions.
Frequently asked questions
Is payback the same as ROI?
No. Simple payback estimates how long annual savings take to recover the stated project cost. ROI expresses return using a defined formula and period. Neither should be labelled as the other.
Should rebates be included in lighting retrofit payback?
You can show a rebate-adjusted scenario when the amount and status are clearly labelled. Include the before-rebate case as well, particularly while approval is pending or reimbursement occurs later.
Can lower wattage alone establish a good LED replacement?
No. Check light output, distribution, visual requirements, controls compatibility and the installation. The proposed energy reduction must come from a solution that suits the space.
