Retrofit payback with maintenance notes
Retrofit payback with maintenance compares annual energy saving and maintenance saving against one project cost.
Payback sequence
Enter the annual savings basis, then compare the project cost with the combined annual benefit.
- 1Enter the annual kWh saved
Use the same savings basis for the payback note.
- 2Enter the energy rate
Convert the kWh saving into annual AUD.
- 3Enter the project cost
Use the same cost scope for the whole note.
- 4Add maintenance saving
Include the annual maintenance value if it is part of the case.
- 5Read both paybacks
Keep the energy-only and maintenance-included values visible.
Application estimate fit
Match the search phrase to one lighting load, period and assumption set before reading the result.
| Search phrasing | Calculator case | Carry forward |
|---|---|---|
| Retrofit payback with maintenance | Annual kWh saving, rate, project cost and annual maintenance saving. | Energy-only payback and payback with maintenance. |
| LED replacement economics | A retrofit case where the kWh saving is already known. | Project cost and maintenance saving kept visible. |
| Upgrade screen | A quick review of whether the annual savings are large enough. | Keep the result in simple-payback terms only. |
| Maintenance offset | A note where maintenance access or lamp replacement changes the business case. | Write the maintenance saving and energy saving as distinct lines. |
Reading the result
Each output belongs to a bounded lighting energy estimate and should travel with its assumptions.
| Output | Technical meaning | Review item |
|---|---|---|
| Payback with maintenance | Project cost divided by energy plus maintenance saving. | This is the preferred payback number in the note. |
| Energy-only payback | Project cost divided by annual energy saving. | Use it as a comparison number. |
| Annual energy saving | Saved kWh multiplied by the entered rate. | Keep the kWh and rate visible. |
| Total annual saving | Energy saving plus annual maintenance saving. | This is the total annual benefit. |
| Project cost | User-entered cost basis for the payback note. | Keep the cost visible beside the result. |
Assumptions that stay visible
Small changes in load, hours, rate or factor can move the result, so the assumptions stay beside the number.
| Assumption | Why it matters | Where it belongs |
|---|---|---|
| Annual kWh saved | Enter the energy reduction as its own input. | Use a known savings basis. |
| Energy rate | The payback changes when the rate changes. | Keep the entered rate visible. |
| Project cost | The cost basis drives the payback period. | Use the same scope through the note. |
| Maintenance saving | Extra annual saving shortens the payback period. | Write the maintenance assumption beside the number. |
retrofit savings case before the number
A useful retrofit payback with maintenance estimate begins with the exact retrofit savings case, not a whole-site average. The same building can include reception lights, display lights, warehouse aisles, amenity rooms and exterior signs that all run for different hours. Naming the group keeps the load, hours and money value tied to one visible lighting job.
That boundary also makes later revision easier. If the fittings, scene level or operating period changes, the row can be revised without rebuilding unrelated areas. Write the space name, fitting family and control group beside the result so another person can check the same case later.
Connected load remains the anchor
Energy and cost estimates move when connected load changes. Count the fittings or enter the load that belongs to the named group, then keep the wattage basis visible. Complete fitting input watts are stronger than a bare lamp value because drivers, control gear and luminaire packages can change the actual load.
The connected-load note does not prove the light level is suitable. A lower load can still be too dim, glary or uneven, while a higher load may support a harder task. Keep lux, beam, colour and measured-light pages nearby when the lighting quality also needs checking.
Hours carry much of the movement
Annual savings basis can move the annual result more than a small wattage change. Seven-day corridors, hospitality scenes, office task rows, seasonal stores and after-hours security lights may all have different operating patterns even when the fittings look similar.
Enter the hours for the same lighting group named in the result. If the group has a normal scene and an after-hours scene, split those cases rather than hiding both in one average. A tidy input line with hours, days and control state is easier to revise than a single unexplained total.
Controls change energy without changing installed load
The retrofit is the control change can reduce energy by shortening operating time or lowering average output. Occupancy sensing, daylight dimming, timeclocks, scene presets and holiday shutdowns all change the energy case while the installed wattage may remain the same.
Keep full connected load and controlled operation visible as different ideas. That separation lets a user compare the installed capacity, the normal operating case and the reduced-energy case without implying that the electrical installation has changed.
Rates and factors are user-entered assumptions
The entered energy rate belongs beside the result because it can change while the lighting kWh stays fixed. A rate comparison, carbon estimate or simple payback note is only as current as the entered cents per kWh, emissions factor or annual saving value.
For Australian lighting notes, keep the rate date, account basis or factor source in the project file if the result will be reused. This page keeps the arithmetic transparent; it does not choose an electricity plan, account structure, rebate or finance outcome.
Read comparisons as bounded arithmetic
Energy-only versus energy-plus-maintenance payback is helpful when the two cases share the same lighting group and schedule basis. Rate A and Rate B, old hours and new hours, or full output and dimmed output should describe the same load before the numbers are compared.
A comparison can show the size of a difference, but it does not decide whether the lighting change is appropriate. Light level, comfort, controls, maintenance access and site operating needs still need their own notes when they affect the decision.
Monthly, annual and period values are different
Monthly values are useful for a short period or a local cost note. Annual values are useful for longer operating schedules, carbon factors and simple payback. After-hours and shutdown values describe only the named period, not the whole lighting account.
Keep the period wording in the result. A monthly cost, an annual kWh value and a holiday shutdown saving should not be compared until the period, hours and days have been made consistent.
Australian energy estimate limits
retrofit payback with maintenance pages on AuLumens are planning estimates for lighting load, kWh, user-entered cost rates, carbon factors or simple payback. They do not model demand items, metered account totals, rebates, tax treatment, electrical design, emergency lighting or certification.
It is a simple payback screen, not a finance model. Keep account-specific charges, landlord agreements, emissions reporting basis and electrical installation details in the appropriate site file. The value of the lighting estimate is that it records the load, period and assumptions before those wider checks begin.
A concise calculation note
A readable note includes the lighting group, connected load, operating period, output state, user-entered rate or factor, and whether the result is monthly, annual or limited to a named period. For split cases, include both sides of the comparison.
Keep the LED replacement and annual kWh pages nearby when the retrofit also needs a load or output note. That context makes the result practical. Another person can change the hours, revise the rate, adjust the control state or compare the result with measured energy data without guessing how the original number was produced.