A bit of confusion exists in the understanding of the requirement for artificial lighting. As part of the current energy efficiency regulations, artificial lighting needs to be calculated to ensure a reasonable level of power usage. The allowances are measured in Watts per square metre as per the following:
- Class 1 (house): 5w/m2
- Class 10 (garage/carport): 3W/m2
- Verandah/Balcony: 4W/m2
There is also an allowance for exterior perimeter lighting. I won’t confuse things by addressing this right now, (it’s all about efficacy, motion sensors, daylight sensors and switching arrangements).
The main confusion is that many people regard the allowable Watts as an indication of the amount of light produced. This is incorrect.
A ‘Watt’ is a measurement of power. Light is measured in ‘Lumens’.
Still confused? Think of an old car and a new car. The old car uses a lot of fuel to travel from A to B. The new car uses less fuel to travel the same distance.
Now think of an old incandescent light globe and a new LED globe. The old incandescent globe uses 100 Watts to light a small room. The new LED globe uses 22 Watts to light the same room.
- 100W incandescent = 1600 Lumens
- 22W LED = 1600 Lumens
So in summary, just as buying more petrol to run an old car requires more money; more Watts to run an old light globe requires more money to be spent on your electricity bill.
When you choose light fittings make sure you choose energy efficient fittings such as LED (Light Emitting Diode) or CFL (Compact Fluorescent). Look for the Lumens to gauge how many you need for the task.
So, how many Lumens do I need?
This depends on your individual requirements, so the below is a general guide, representing the amount of light needed in typical areas. All you need to do is multiply the area of the room by the number of lumens required.
- In dining rooms and corridors you will need around 10 – 20 lumens per square metre.
- Kitchens and rooms where you read casually will require more lighting, around 20 – 55 lumens per square metre.
- Rooms for more intensive reading or study need to be better lit, with a lumens requirement of around 55 – 110 per square metre.
As an added extra we can provide a room by room lumen calculation with our energy compliance reports.