# LED Conversion Savings and Payback Calculator Annual kWh, annual cost and payback period for converting existing luminaires to LED — with ballast loss counted and equivalence matched on lumens. Published: 2026-09-06 · Last updated: 2026-09-06 ## Contents 1. Worked example 2. Short answer 3. Ballast loss: the watts you actually pay for 4. Match on lumens, not on watts 5. The electricity price to use 6. What the payback figure leaves out 7. When conversion is not the right answer 8. What to send us for a quote ## Calculator Annual kWh, annual cost saved and payback period when you convert existing luminaires to LED. Note: This page contains an in-browser calculator; results are computed instantly from your inputs and no data is sent to a server. The full method is explained below. ## Worked example Opened with its default case — **Number of luminaires / lamps: 200 · Existing luminaire type: Fluorescent 2×36 W (≈86 W with low-loss ballast) · Existing power (W) — if entering manually: 86** — the calculator returns the figures below. They are written out here so the output is readable without running JavaScript: in print, with scripts disabled, or by a search engine. Worked example — inputs | Input | Value | | --- | --- | | Number of luminaires / lamps | 200 | | Existing luminaire type | Fluorescent 2×36 W (≈86 W with low-loss ballast) | | Existing power (W) — if entering manually | 86 | | Equivalent LED power (W) | 42 | | Operating hours per day | 10 | | Operating days per year | 300 | | Electricity unit price (TRY/kWh) | 0 | | LED luminaire unit price (TRY) | 0 | | Installation cost per point (TRY) | 0 | Worked example — results | Result | Value | | --- | --- | | Annual kWh saved | 26,400 kWh/year | | Total investment | Enter a unit price | | Reduction in connected load | 51.2% (8.8 kW) | Change any field above and the calculator recomputes; this table is the default case only. ## How do you calculate the saving from an LED conversion? Four numbers decide it, and the first one is the one most often got wrong. **(1) The real power of what you have now** — a 2×36 W fluorescent luminaire does not draw 72 W; with a low-loss ballast it draws about 86 W, and with an old magnetic ballast more. **(2) The LED power that produces the same light**, matched on lumens rather than watts. **(3) The annual operating hours** (hours per day × days per year). **(4) The net-of-VAT electricity price per kWh**, distribution charges included. The saving is **(existing W − LED W) × points × annual hours ÷ 1000 × price**, and the payback is the investment divided by that. Ignoring ballast loss understates the saving by 15–20%; matching on watts instead of lumens overstates it and leaves the space too dark, which is the failure mode that gets a conversion reversed. ## Ballast loss: the watts you actually pay for A discharge lamp cannot run directly from the mains; it needs control gear, and that gear consumes power itself. The lamp label states the lamp, not the system. Every honest comparison starts from the system figure, because that is what the meter records. Lamp watts against system watts | Existing luminaire | Lamp watts | Typical system watts | Loss added by the gear | | --- | --- | --- | --- | | Fluorescent 1×58 W, low-loss ballast | 58 W | ≈ 67 W | ≈ 16% | | Fluorescent 2×36 W, low-loss ballast | 72 W | ≈ 86 W | ≈ 19% | | Fluorescent 4×18 W office panel | 72 W | ≈ 100 W | ≈ 39% | | Mercury vapour 250 W | 250 W | ≈ 275 W | ≈ 10% | | Metal halide 400 W | 400 W | ≈ 460 W | ≈ 15% | | High-pressure sodium 400 W | 400 W | ≈ 465 W | ≈ 16% | These are typical figures for low-loss magnetic gear, which is what is normally found in an installation old enough to be worth converting. Older high-loss ballasts add more; electronic ballasts add less. If the luminaire has a nameplate stating system watts, use that in preference to the table. ## Match on lumens, not on watts The most common conversion mistake is buying an LED of roughly half the existing wattage because “LED is about twice as efficient”. Efficiency varies by a factor of two *within* the LED category, so the correct replacement wattage depends on which LED you buy. The same 6,600 lm, three ways | LED efficacy | Wattage needed for 6,600 lm | What it is | | --- | --- | --- | | 105 lm/W | ≈ 63 W | Budget product, often unbranded | | 160 lm/W | ≈ 42 W | Current mainstream efficient product | | 210 lm/W | ≈ 32 W | Premium, high-efficacy product | The saving against an 86 W fluorescent is 27% with the first, 51% with the second and 63% with the third. The price gap between them is usually smaller than the energy gap over the life of the installation, which is why efficacy in lm/W belongs in the enquiry alongside the wattage. Two further figures change what “equivalent” means. **Luminaire lumens are not lamp lumens**: a fluorescent luminaire loses light in the reflector and diffuser, so an LED luminaire quoted on output lumens can be lower than the lamp figure and still be brighter on the working plane. And **distribution matters**: a wide-beam LED in a tall space wastes light on the walls. Where the layout changes, compare on lux at the working plane, not on lumens at the ceiling. ## The electricity price to use Use the price you actually pay per kilowatt-hour, net of recoverable VAT, with distribution charges and levies included. Taking only the energy component understates the saving significantly, because the non-energy components of an industrial bill are substantial and are avoided along with the consumption. The arithmetic is linear in price, so the payback figure moves directly with the tariff: if the price rises 20%, the payback period falls by about a sixth. For a conversion that pays back in more than three years at today’s tariff, it is worth running the calculation again at the tariff you expect rather than the one you have. ## What the payback figure leaves out Simple payback — investment divided by annual saving — is the right figure for a first decision and the wrong one for a final one. Three things it omits, all of which make LED look better than the number suggests: 1. **Maintenance avoided.** Lamp and ballast replacement over the life of the installation is a real recurring cost, and in high-bay or external lighting the access equipment costs more than the lamp. 2. **Cooling load.** In an air-conditioned space, every watt of lighting is also a watt of heat that has to be removed. The electrical saving is followed by a smaller but real cooling saving. 3. **Failure profile.** Discharge lamps dim substantially before they fail, so an installation nearing end of life is already delivering less light than it was specified for. The comparison is usually being made against a system that is under-performing. One thing it omits in the other direction: LED output also declines, and a product’s rated life is stated at a light-output level (L70, L80, L90) that must be read alongside the hours. A 50,000-hour L70 product and a 50,000-hour L90 product are not the same purchase. ## When conversion is not the right answer Three cases where the calculation will show a saving and the project still should not go ahead as a straight lamp-for-lamp swap. **Very low operating hours:** a store room lit two hours a week will not pay back within any reasonable horizon, whatever the tariff. **A luminaire layout that was wrong to begin with:** if the existing lighting does not meet the required lux level, replacing it one-for-one preserves the fault — that is a design job, not a conversion. **Emergency and safety lighting:** those luminaires have their own duration and testing requirements and are replaced as a system, not as a lamp. ## What to send us for a quote Send the calculator output with the count by luminaire type, the mounting height and the space in question (office, warehouse aisle, external yard). Mounting height and area decide the beam distribution, which is what makes an offer comparable. We quote luminaires, drivers, mounting accessories and the installation consumables as one list, delivered to site on one invoice. ## Frequently Asked Questions What LED wattage replaces a 36 W fluorescent tube? Not 18 W. A 36 W T8 tube produces roughly 3,350 lm, so at 160 lm/W the LED needs about 21 W, and at a budget 105 lm/W about 32 W. Match on lumens, and remember that the fluorescent system also drew ballast loss on top of the 36 W. Why is my fluorescent luminaire drawing more than the lamp rating? Because the ballast consumes power too. A 2×36 W luminaire with low-loss magnetic gear draws about 86 W at the meter rather than 72 W, and a 4×18 W office panel about 100 W. The saving is calculated against the system figure, which is why the calculator uses it. How long should an LED conversion take to pay back? In a space lit 3,000 hours a year at a typical industrial tariff, a well-specified conversion usually pays back in one to three years. Beyond four years, check the operating hours and the LED efficacy you assumed — one of the two is usually the reason. Does the calculation include maintenance savings? No, deliberately. It reports simple energy payback only, so the figure is conservative and cannot be accused of double counting. Avoided lamp and ballast replacement, and the access equipment that goes with it, shorten the real payback further. Can I keep the existing luminaire and fit an LED tube? Sometimes, but it is a decision about the control gear, not the tube. A retrofit tube either requires the ballast to be bypassed or is designed to run on the existing one — the two are not interchangeable, and the work must be recorded on the luminaire so the next person does not fit the wrong type. Tell us which route you intend and we will quote the matching product. Do you supply the luminaires and the installation materials together? Yes — luminaires, drivers, mounting kits, cable and connectors on one quote and one invoice, delivered to site. Send the calculator output with the mounting height and we will come back within one business day. ## Related guides ### Fluorescent to LED: The Replacement Table That Actually Works Why an 18 W tube is not replaced by an 18 W LED. [Read more](https://aksco.com.tr/en/insights/fluorescent-to-led-replacement-guide/) ### Electrical & Lighting Luminaires, lamps, drivers, cable and accessories in one quote. [Read more](https://aksco.com.tr/en/products/electrical-lighting/) ### Supplier Evaluation Scorecard Score lighting suppliers on eight weighted criteria. [Read more](https://aksco.com.tr/en/tools/supplier-evaluation-scorecard/) ## Send your list — your quote is ready within 1 business day. A list, a photo or an Excel file — whatever is easiest. On standard items most quotes go out the same business day. Custom production, imports or 50+ line lists can take longer; when they do, we tell you the timeline in writing on the day we receive the request. [Request a Quote](https://aksco.com.tr/en/request-a-quote/)[Message on WhatsApp](https://wa.me/905343356922) --- AKSCO Ticaret ve Tedarik — https://aksco.com.tr AKSCO Ticaret ve Tedarik · Esentepe Mah. Talat Paşa Cad. No:5 İç Kapı No:1, Şişli/İstanbul Türkiye'nin 81 ili ve uluslararası sevkiyat info@aksco.com.tr · 0534 335 69 22