The levels which must be achieved for different building types are quoted below. These figures must be based on a weighted average calculation based on all luminaires used in the building.
Offices, industrial and Storage buildings
- not below 40 luminaire - lumens/circuit watt. (A maximum of 500W of
installed capacity in the building is exempt from this calculation allowing
flexibility for the use of feature lighting.)
Other buildings - not below 50 luminaire - lumens/circuit
watt except for display lighting
Display lighting - installed capacity of display lighting
not below 15 luminaire - lumens/circuit watt
Note Circuit watts = power consumed
in lighting circuits by lamps gear and power factor correction equipment.
For example imagine a building with only two luminaire types, 100 x Merlin
1 x 35W 30% up 70% down in the offices (MER2R13570S) and 200 – 250W
Harrier Metal Halide (Venture lamp) Low Bays with rack reflectors in the
factory (HRR250H). The calculation for the building would be as follows
| Position | Offices | Factory | Total | |
| Number | 100 | 200 | ||
| Description | 100 Merlin 1 x 35W | 200 Harrier 250W | ||
| Circuit Watts per luminaire | 39 | 271 | ||
| Lamp Lumens per luminaire | 3300 | 23600 (Venture) | ||
| Luminaire L.O.R. | 0.868 | 0.810 | ||
| Luminaire control correction factor | 1 (no control) | 1 (no control) | ||
| Total corrected luminaire output - number of luminaires x lamp (Cl) lumens per luminaire at 100 hours x LOR/Cl | 286,440 | 3,823,200 | 4,109,640 | |
| Total Circuit watts | 3,900 | 54,200 | 58,100 |
Without controls, by dividing total circuit watts into the total corrected luminaire output (4,109,640/58,100) we arrive at a weighted average luminaire lumens per circuit watt of 70.73, well in excess of the target of 40. With a single form of control or approved switching the figure achieved would be increased to 88.41. (70.73/0.8).