Choosing Bulbs


An energy efficient bulb box has lots of useful information on it to help you choose the right light for you.


Like standard incandescent light bulbs, you'll need to make sure the base of the new bulb (bayonet or screw fitting) is the same as the one you're replacing. If it doesn't fit, don't force it.


You may also see lumens (lm) on packaging, to indicate brightness. While wattage measures the energy a light bulb uses, light output is actually measured in lumens - the higher the lumens, the brighter the light. Both will appear on most light bulb packaging, which can be helpful when you want to find which bulb uses the least energy for the most light output. So think lumens for brightness not watts (W).
Energy efficient bulbs produce more light with less energy than standard incandescent bulbs, so if you're replacing a 100 W incandescent bulb, you'll only need to use a 20 to 24 W CFL or 15 to 18 W LED.


How much energy the bulb uses is measured in watts (W). The higher the wattage, the more the bulb costs to run.
Check the packaging of the efficient bulb to find the correct wattage and lumens. A 75 W standard incandescent is approximately equivalent to an 18 - 20 W CFL, 52 W halogen and 12 - 15 W LED.

Standard Incandescent Bulb
40 W (415 lumens)
60 W (710 lumens)
75 W (920 lumens)
100 W (1300 lumens)
Equivalent New Generation Halogen
28 W
42 W
52 W
70 W
Equivalent Compact Fluorescent
12 W
15 W
18/20 W
20/24 W
Equivalent Light Emitting Diode (LED)
6-9 W
9-12 W
12-15 W
15-18 W

Light efficiency

How efficiently the bulb converts electricity into light is measured in lumens per watt (lm/W). The higher the lumens per watt, the more efficient a bulb is.

Colour temperature

We measure how warm or cool a light is in kelvins (K) and refers to the colour. A "warm" light provides a more yellow light, whereas a "cool" white light has more blue - the higher the number of kelvin, the whiter the light.
‘Warm white' is roughly the same colour as standard incandescent light bulbs and is is usually around 2,700 - 3,000 K. It helps enrich the warm colours in your home, and is suitable for lounges, hallways and bedrooms.
A ‘cool white’ is usually around 4,000 - 6,500 K, gives off a bluer light that improves contrasts. It is good for task lighting and gives the ‘bright' light you might prefer to use in kitchens, laundries, bathrooms and offices.


The number of hours a bulb should last when in use.
Standard incandescent bulbs have a typical lifetime of 1,000 hours, CFLs around 6,000 - 8,000 hours and LEDs at least 15,000 hours (based on manufacturers’ information).


The amount of mercury a bulb contains. CFLs must not contain more than 5mg of mercury. Halogens and LEDs contain no mercury.

Special features

Light fittings with special features or functions (like dimmable lights, bathroom fan lights and chandeliers) need compatible light bulbs. Check light bulb packaging to find ones with the functionality you need.