Lighting can typically constitute between 3% and 15% of total electricity use in a commercial building. The proportion will vary widely based on such aspects as:
- Building type (office, university, factory, shipyard, warehouse)
- Hours of operation (day/night, shifts)
- Wattage
- Control of lamps
- Skylights
Whilst a modern 9-5 office might be expected to be consuming around 10% of its electricity on lighting, a factory might be using less than 5% on light because of the significant energy users on site such as compressors, chillers, ventilation, motors and pumps. In such cases, production and operation processes are likely to carry greater energy and cost saving benefits than addressing lighting alone. In contrast to a factory, a logistics warehouse might have high bay lamps of up to 400 Watts each and no mechanical ventilation, cooling or process operations. As such, lighting might constitute significantly higher amounts.
In all cases, lighting can be measured by its circuit wattage. The combined wattage of the lamp and its associated ballast.
By knowing the wattage of the lamp and ballast/starter, the number of lamps and the hours per day/week/year that they operate, a good understanding of energy use in kWh will be available.
Taking replacement LED solutions that provide similar lumens per watt will result in lower wattages. Typically LED replacements will be around 50% lower wattage.
Clearly by replacing these older lamps with LEDs, energy can be reduced by a more than half, provided lamps are on for the same hours per day/week/year. Furthermore, additional savings can be made at install through:
- Installation of presence sensors
- Installation of daylight sensors
- Reduced cost in replacing failed lamps
- Revising the layout of lighting units
As such, savings available can be of the order of 80% if the work is properly planned and appropriate lamps and luminaires are specified.
It should be borne in mind that whilst LED technology has advanced rapidly and prices have reduced significantly, there are still products on the market that are not fit for purpose. As such, care should be taken in selection.
It should also be recognised that LED technology for lighting purposes is still relatively new and should not be used in every application. There remain concerns over the long-term health effects of blue light and its affects upon the human body clock (circadian rhythms).
