# LED against fluorescent: what actually drives the saving > Why operating hours matter more than wattage when comparing LED with fluorescent, and how the same two fittings give opposite answers in different buildings. Source: https://commercialepcupgrades.co.uk/guides/led-vs-fluorescent-running-costs --- # LED against fluorescent: what actually drives the saving The question people ask is which fitting uses less power. The question that decides the answer is how many hours it is on. A saving per hour is worth very little in a building lit for six hours a day and a great deal in one lit continuously, which is why payback figures quoted without the hours behind them are close to meaningless. Payback is around a year under continuous operation, and longer on shorter hours. ## Where a payback figure comes from Four numbers: the power difference between old and new, the number of hours the lighting runs, the price you pay per unit of electricity, and the installed cost of the change. Alter any one and the answer moves, sometimes dramatically. Operating hours are the one that varies most between buildings, and the one most often left unstated. A quote claiming a two-year payback has assumed a number of hours. Ask which, and check it against your building rather than against the industry average it probably came from. ## The same fittings, two buildings Consider the identical upgrade in two buildings. An office lit from eight until six on weekdays runs its lighting roughly two and a half thousand hours a year. A distribution building running two shifts six days a week runs perhaps twice that, and a continuous operation more again. The energy saved per hour is the same in both. The annual saving is not, and neither is the payback. The warehouse case is strong on numbers the office case simply cannot reach, and that is before any of the other differences between those buildings. ## What else is in the comparison and usually left out - Lamp replacement labour. Fluorescent tubes fail and get replaced, repeatedly, often at height. That recurring cost disappears with LED and rarely appears in the comparison. - Disposal. Fluorescent tubes contain mercury and are hazardous waste, with a cost attached each time. - Cooling. In an air-conditioned building, lighting heat is removed at further cost, so the saving is larger than the lighting bill alone. - Light quality and light levels. A like-for-like wattage comparison ignores whether the space ends up better lit, which is usually the point of doing it. - Availability. The lamp types are being withdrawn in phases, so part of the comparison is against a future where replacements are harder to source. ## Where the honest answer is "not yet" A building lit a few hours a day, with sound recent fittings and no compliance pressure, has a long payback and no particular reason to hurry. Saying so is more useful than producing a business case that only works on optimistic hours. The reasons to move anyway are a compliance deadline, a refurbishment that makes the access free, or fittings approaching end of life. Absent all three, a short-hours building can reasonably wait. ## Questions we get asked ### How much cheaper is LED than fluorescent to run? ### What payback should I expect? ### What gets left out of the comparison? ### Is there a case for waiting? Sources - Payback on a commercial LED retrofit depends primarily on operating hours: around a year where lighting runs continuously, and longer in a building lit for normal office hours. [LED revolution puts lighting top of the energy efficiency agenda, Carbon Trust, 2014](https://www.carbontrust.com/news-and-insights/insights/led-revolution-puts-lighting-top-of-the-energy-efficiency-agenda) Where this page describes costs or savings it gives a general range rather than a quoted figure, because the numbers depend on your building, your operating hours and the equipment being replaced. A contractor gives you a figure after a survey. Last updated 8 October 2026 . - [Lamp swap or new fittings The other half of the decision](https://commercialepcupgrades.co.uk/guides/lamp-swap-vs-fixture-replacement) - [What it costs The installed cost side of the sum](https://commercialepcupgrades.co.uk/cost) - [Long-hours buildings Where the numbers work hardest](https://commercialepcupgrades.co.uk/buildings/warehouse) Next step ## Find out what your building actually needs Tell us the building type, the floor area and the rating you are on now. One commercial contractor comes back to you with a quote. No panel, no cold calls. Or call [07367 293494](tel:+447367293494). Monday to Friday, 9am to 5.30pm.