The environmental argument for LED lighting is usually made in general terms. On a commercial or industrial project the argument that actually carries weight is narrower and more useful: what the installation costs to run, how quickly the difference pays back the capital, and what happens to that calculation when the grid is unreliable.
Where the saving comes from
An LED converts far more of its input power into visible light than the technologies it replaces, and it directs that light where it is wanted rather than radiating it in all directions. In practice, replacing a 400W metal halide highbay with a modern 150W LED equivalent delivers comparable or better light on the working plane at a little over a third of the connected load.
Two additional factors are easy to overlook and often larger than expected:
- Reduced cooling load. Lighting that produces less waste heat lowers the demand on air conditioning. In an air-conditioned interior this can add a meaningful fraction on top of the direct lighting saving.
- Maintenance avoided. Relamping a high bay or a street light is a scaffold, a cherry picker or a road closure. On inaccessible installations the labour saved over ten years frequently exceeds the electricity saved.
Working out payback honestly
A defensible payback calculation needs four inputs, and the third is the one most often guessed at.
- Connected load before and after, in kilowatts, using real luminaire wattages rather than nominal lamp ratings – the ballast or driver loss counts.
- Annual operating hours. A warehouse on two shifts and a reception area on a timer are entirely different cases.
- Your actual tariff, in Rand per kilowatt-hour, including the demand charge where one applies. Many commercial tariffs price peak demand separately, and reducing connected load can cut that charge as well as the consumption charge.
- Installed cost, including labour and any control gear, not the price of the fittings alone.
Our ROI calculator works through this with South African defaults, and will show the payback period as well as the annual saving.
Load-shedding changes the arithmetic
In South Africa, reduced connected load is worth more than the tariff saving alone suggests.
Lower lighting load means a smaller inverter or UPS is needed to keep a site operating, or that an existing one runs longer on the same battery. On sites with generator backup, reduced load means less diesel burned during every outage. Where a solar installation is being considered, cutting the lighting load first reduces the size and cost of the array required – it is almost always cheaper to reduce demand than to generate more supply.
Solar-powered luminaires with integrated batteries take this further for perimeter, security and area lighting, removing those circuits from the supply entirely and from the trenching schedule as well.
Controls usually beat further efficiency gains
Once a site has moved to efficient luminaires, the next saving rarely comes from a more efficient product. It comes from not lighting empty space.
- Occupancy sensing in storerooms, stairwells, ablutions and aisles, where lights routinely burn for hours with nobody present.
- Daylight harvesting near glazing and rooflights, dimming to maintain a target level rather than running at full output regardless of conditions.
- Time scheduling for areas with predictable occupancy.
- Task tuning – many spaces are lit well above the level their use requires, and dimming to the correct level saves energy while improving comfort.
These are frequently the shortest-payback measures available on a site that has already been relamped.
What to check before believing an efficiency claim
Not every stated saving survives contact with a project.
- Compare delivered lumens, not watts. A lower wattage that does not meet the required illuminance is not a saving, it is an under-lit space.
- Check efficacy at the CCT and CRI you are specifying, not the manufacturer’s best-case combination.
- Ask for the L rating. A product that has faded to 70% output by year four has quietly given back much of its advantage.
- Confirm the driver. An efficient LED behind a poor driver will not deliver the projected life, and replacement labour erodes the saving.
- Model the real operating hours. Savings quoted at 24-hour operation flatter any product.
End of life
LEDs contain no mercury, which distinguishes them from the fluorescent and discharge lamps they replace and removes a hazardous waste stream from the site. They do contain recoverable aluminium and electronics, and should go to e-waste handling rather than to landfill. Because a well-built luminaire lasts far longer than the lamps it replaces, the volume of material moving through the waste stream falls considerably over the life of a building.
In short
The environmental case and the commercial case point the same way, but they are strongest when argued specifically. Real wattages, real operating hours, your real tariff, and an honest view of maintenance access will produce a number that stands up in a budget meeting – and on most commercial and industrial sites in South Africa, that number is comfortably in favour of the change.
If you would like this worked through for a specific site, send us the details and our technical team will help.
